Bacteriology


(Courtesy of Dr. Charles C. Shepard, Public Health Image Library, Centers for Disease Control and Prevention.)


a. Borderline tuberculoid leprosy


b. Lady Windermere syndrome


c. Lepromatous leprosy


d. Scrofula


e. Tuberculoid leprosy


182. An 85-year-old homeless man is brought to the emergency room. He says that he has been living on the street for the past 10 years. There is a strong smell of alcohol on his clothing and you suspect he is an alcoholic. He says he has constant headaches, and a fever that comes and goes about every 5 days. He also complains of great pains in his legs. The nurses say that when they cut off his clothes, they found lice. You suspect that he has trench fever caused by which organism?


a. Bacillus anthracis


b. Brucella abortis


c. Bartonella bacilliformis


d. Bartonella henselae


e. Bartonella quintana


183. A 45-year-old man goes to his family doctor complaining of a constant, non-productive cough. The man also has severe chest pains which he says have bothered him for the past week. The man also says that this is unusual for him because it is summer and he usually gets his “colds” in the winter and not in July. When the physician examines the man’s chest, he hears an abnormal or pathological sound upon auscultation. The man had pneumonia with consolidation in both lobes. No organism was isolated from his sputum on blood agar, but the physician gave him a shot of penicillin “just in case”. As it turned out, the penicillin shot did nothing to relieve the man’s distress. After 96 hours, a Gram-negative bacterium from the man’s sputum did grow on buffered charcoal yeast extract. What disease did this man have?


a. Legionnaires’ disease


b. Lobar pneumonia caused by Klebsiella pneumoniae


c. Lobar pneumonia caused by Streptococcus pneumoniae


d. Psittacosis


e. Tuberculosis


184. At a state dinner, the menu included steak or fried chicken, baked potato or homemade potato salad, green beans, and a “green” salad. The salad dressing was either Italian or Russian. Dessert included either chocolate cake or apple pie. The beverage was water, iced tea, or coffee. After 3 hours, only the diners who had eaten the potato salad, became violently ill with vomiting, stomach cramps, and/or diarrhea. It became immediately obvious that the source of the food poisoning was the potato salad. When the potato salad was sent to a clinical microbiology lab, which of the following bacteria was isolated in large numbers?


a. Bacillus cereus


b. Clostridium botulinum


c. Escherichia coli


d. Staphylococcus aureus


e. Staphylococcus epidermidis


185. A young boy, 9 years of age, is outside playing in the summer in Texas and steps on a board with a rusty nail in it. The nail goes right through his gym shoe and enters his right foot. He does not tell his parents about it because he is sure his mother will yell at him because she is always telling him not to do what he just did. He is also afraid she will curtail his playing outside privileges. Besides, it did not bleed much and the bleeding stopped before he went in for supper. Besides, the boy’s family did not believe in going to the doctor for every little thing. In fact, the boy cannot remember the last time he saw a doctor. About a week later, the boy developed a sore throat and then 4 days later his parents did take him to the hospital (reluctantly) with difficulty in swallowing, talking, and breathing. Also, the boy began to experience muscle spasms. The hospital doctor recognized the signs of tetanus and immediately administered tetanus immune globulin. The doctor asked the parents when the last time the boy had received a tetanus shot and they replied that they did not know. After being in the hospital for a week, the boy unfortunately died of respiratory failure. This unfortunate incident occurred because which of the following facts represents the best answer?


a. The causative organism, Clostridium tetani, is a strict anaerobe


b. The causative organism, Clostridium tetani, is a strict aerobe


c. The causative organism, Clostridium tetani, produces a potent heat-labile neurotoxin


d. The causative organism, Clostridium tetani, is a spore producer, a strict anaerobe, and produces a potent heat-labile neurotoxin


e. The causative organism, Clostridium tetani, is a spore former, a strict aerobe, and produces a potent heat-labile neurotoxin


186. A 6-year-old girl in Russia developed a sore throat and was taken to the doctor by her parents. The doctor diagnosed a “strep throat” and gave her a shot of penicillin. The penicillin shot did not help, and the child’s health worsened and she was brought back to the doctor. Now the child complained of more than a sore throat. Now she refused to eat and was very lethargic. She also had a fever of 40°C. When the doctor reexamined the child, he observed a normal chest sound, a productive pharyngitis, and inflamed cervical lymph nodes. A throat culture did not reveal any Group A streptococci, and the child was becoming increasingly lethargic. The doctor then noticed a structure in the back of the child’s throat that looked like a leather membrane. The parents told the doctor when he asked that the girl had received no vaccinations. The doctor then knew what disease he was observing. The organism most likely to be the causative agent of this infection was which of the following?


a. Bacillus anthracis


b. Clostridium botulinum


c. Clostridium perfringens


d. Clostridium tetani


e. Corynebacterium diphtheriae


187. A patient with a burning epigastric pain is admitted to the hospital, and a gastric biopsy is performed. The tissue is cultured on chocolate agar incubated in a microaerophilic environment at 98.6°F (37°C) for 5 to 7 days. On fifth day of incubation, colonies appear on the plate and curved, gram-negative, oxidase-positive rods are observed. Which of the following is the most likely identity of this organism?


a. Campylobacter fetus


b. Campylobacter jejuni


c. Haemophilus influenzae


d. Helicobacter pylori


e. Vibrio parahaemolyticus


188. A 2-year-old boy who missed several scheduled immunizations presents to the emergency room with a high fever, irritability, and a stiff neck. Fluid from a spinal tap reveals 20,000 white blood cells per milliliter with 85% polymorphonuclear cells. Gram stain evaluation of the fluid reveals small pleomorphic gram-negative rods that grow on chocolate agar. If an inhibitor is designed to block its major virulence, which of the following would be the most likely major virulence factor?


a. Capsule formation


b. Endotoxin assembly


c. Exotoxin liberator


d. Flagella synthesis


e. IgA protease synthesis


189. A local community is in distress due to a natural disaster. After consuming contaminated water, many individuals experience nausea, vomiting, and diarrhea that produce stools resembling rice water. An experimental compound is discovered that prevents the activation of adenylate cyclase and the resulting increase in cyclic adenosine monophosphate (AMP). The toxic effects of which of the following bacteria would most likely be prevented with the use of this experimental compound?


a. Brucella abortus


b. Corynebacterium diphtheriae


c. Listeria monocytogenes


d. Pseudomonas aeruginosa


e. Vibrio cholerae


190. A single, 30-year-old woman presents to her physician with vaginitis. She complains of a slightly increased, malodorous discharge that is gray-white in color, thin, and homogenous. Clue cells are discovered when the discharge is examined microscopically. Which of the following organisms is the most likely cause of her infection?


a. Candida albicans


b. Trichomonas vaginalis


c. Escherichia coli


d. Gardnerella vaginalis


e. Staphylococcus aureus


191. A 12-year-old girl begins to limp while playing soccer. She has pain in her right leg and upper right thigh. Her temperature is 102°F. X-ray of the femur reveals that the periosteum is eroded. Assuming that this case is managed as an infectious disease, which of the following is the most likely etiologic agent?


a. Listeria monocytogenes


b. Salmonella enteritidis


c. Staphylococcus saprophyticus


d. Staphylococcus aureus


e. Streptococcus pneumoniae


192. A scraping from a painful, inflamed wound is found to contain numerous gram-negative bacteria. Upon questioning, the feverish patient states that he was bitten by a cat while trying to rescue it from a storm drain earlier in the day. Given these observations, which of the following organisms is the most likely cause of infection?


a. Aeromonas species


b. Campylobacter jejuni


c. Pasteurella multocida


d. Pseudomonas aeruginosa


e. Yersinia enterocolitica


193. A 40-year-old male, who was in good health earlier, begins experiencing a chronic cough. Over the following 6 weeks, the cough gradually worsens and becomes productive. He is also coughing up blood, and notes weight loss, fever, and night sweats. A sputum sample is positive for acid-fast bacilli. Which of the following pathogenic mechanisms can be primarily attributed to the etiologic agent involved in this disease?


a. Cell-mediated hypersensitivity


b. Clogging of alveoli by large numbers of acid-fast mycobacteria


c. Humoral immunity


d. Specific cell adhesion sites


e. Toxin production by the mycobacteria


194. A person living on streets is infected with an invasive salmonella organism that is resistant to most of the antibiotics that could be considered for treatment. It did show sensitivity to quinolones that are bacteriocidal. Which of the following is the best explanation of their mode of action on growing bacteria?


a. Inactivation of penicillin-binding protein II


b. Inhibition of β-lactamase


c. Inhibition of DNA gyrase


d. Inhibition of reverse transcriptase


e. Prevention of the cross-linking of glycine


195. A high school student with a natural immunodeficiency is treated aggressively with a variety of potent antibiotics to overcome several bacterial infections. The most recent problem is caused by S. aureus, which is reported to be vancomycin-indeterminate (VISA). Which of the following statements concerning VISA is correct?


a. Patients with VISA isolates need not be isolated


b. Minimum inhibitory concentration (MIC) for vancomycin is at least 1.0 mcg/mL


c. VISAs have emerged because of the extended use of vancomycin for methicillin-resistant Staphylococcus aureus (MRSA)


d. VISA isolates are infrequent, so surveillance at the present time is not warranted


e. VISA isolates are usually methicillin susceptible


196. A 3-year-old girl, who has missed several scheduled immunizations, presents to the emergency room with a fever and troubled breathing. A sputum sample is brought to the laboratory for analysis. Gram stain reveals the following: rare epithelial cells, 8 to 10 polymorphonuclear leukocytes per high-power field, and pleomorphic gram-negative rods. As a laboratory consultant, which of the following interpretations is correct?


a. The appearance of the sputum is suggestive of H. influenzae


b. The patient has pneumococcal pneumonia


c. The patient has Vincent disease


d. The sputum specimen is too contaminated by saliva to be useful


e. There is no evidence of an inflammatory response


197. A 25-year-old medical student presents with a ruptured appendix. A peritoneal infection develops, despite prompt removal of the organ and extensive flushing of the peritoneal cavity. An isolate from a pus culture reveals a gram-negative rod identified as Bacteroides fragilis. Anaerobic infection with B. fragilis is best characterized by which of the following?


a. A black exudate in the wound


b. A foul-smelling discharge


c. A heme-pigmented colony formation


d. An exquisite susceptibility to penicillin


e. Severe neurologic symptoms


198. Several days after an unprotected sexual encounter, a healthy 21-year-old male develops pain and pus on urination. A Gram stain reveals gram-negative diplococci. Which of the following structures is responsible for adherence of the offending microbe to the urethral mucosa?


a. Capsule


b. Fimbriae


c. Flagella


d. F pili


e. Peptidoglycan


f. Lipopolysaccharide (LPS)


199. A 1-week-old newborn develops meningitis. Short, gram-positive rods are isolated. History reveals that the mother had eaten unpasteurized cheese from Mexico during pregnancy, and she recalled having a flu-like illness. Which of the following is the most likely etiologic microorganism?


a. Corynebacterium diphtheriae


b. Escherichia coli


c. Group B streptococci


d. Listeria monocytogenes


e. Streptococcus pneumoniae


Questions 200 to 203


200. A 30-year-old male patient is seen by the emergency service and reports a 2-week history of a penile ulcer. He notes that this ulcer did not hurt. Which of the following conclusions/actions is most valid?


a. Draw blood for a herpes antibody test


b. Even if treated, the lesion will remain for months


c. Failure to treat the patient will have no untoward effect, as this is a self-limiting infection


d. Perform a dark-field examination of the lesion


e. Prescribe acyclovir for primary genital herpes


201. The laboratory reports that the Venereal Disease Research Laboratory (VDRL) test performed on the above patient is reactive at a dilution of 1:4 (4 dils). The patient also reports to you that he has recently been diagnosed with hepatitis A. Which one of the following is most appropriate next step in management?


a. Order a confirmatory test such as the fluorescent treponemal antibody (FTA) test


b. Order a rapid plasma reagin (RPR) test


c. Perform a spinal tap to rule out central nervous system (CNS) syphilis


d. Repeat the VDRL test


e. Report this patient to the health department, as he has syphilis


202. In the same patient from the previous vignette, which of the following test combinations for syphilis is most appropriate?


a. FTA-Abs (IgG)/FTA-Abs (IgM)


b. RPR/culture of the lesion


c. RPR/FTA-Abs


d. Treponema pallidum hemagglutination (TPHA)/microhemagglutination—Treponema pallidum (MHTP) tests


e. VDRL/RPR


203. Assume that the same patient from the previous vignette absolutely denies any contact, sexual or otherwise, with a person who had syphilis. Also assume that both the RPR and the FTA-Abs are positive on this patient. Which of the following tests could be used to show that this patient probably does not have syphilis?


a. Frei test


b. MHTP test


c. Quantitative RPR


d. Treponema pallidum immobilization (TPI) test


e. VDRL


204. A patient is hospitalized after an automobile accident. The wounds become infected, and the patient is treated with tobramycin, carbenicillin, and clindamycin. Five days after antibiotic therapy was initiated, the patient develops severe diarrhea and pseudomembranous enterocolitis. Antibiotic-associated diarrhea and the more serious pseudomembranous enterocolitis can be caused by which of the following organisms?


a. Bacteroides fragilis


b. Clostridium difficile


c. Clostridium perfringens


d. Clostridium sordellii


e. Staphylococcus aureus


205. A 2-year-old child has a fever, stiff neck, and is irritable. Gram stain smear of spinal fluid reveals gram-negative, small pleomorphic coccobacillary organisms. What is the most appropriate procedure to follow in order to reach an etiological diagnosis?


a. Culture the spinal fluid in chocolate agar, and identify the organism by growth factors


b. Culture the spinal fluid in mannitol-salt agar


c. Perform a catalase test of the isolated organism


d. Perform a coagulase test with the isolate


e. Perform a latex agglutination (LA) test to detect the specific antibody in the spinal fluid


206. A patient complains to his dentist about a draining lesion in his mouth. A Gram stain of the pus shows a few gram-positive cocci, leukocytes, and many-branched gram-positive rods. Branched yellow sulfur granules are observed by a microscope. Which of the following is the most likely cause of the disease?


a. Actinomyces israelii


b. Actinomyces viscosus


c. Corynebacterium diphtheriae


d. Propionibacterium acnes


e. Staphylococcus aureus


207. A 39-year-old primigravid Caucasian female lawyer develops premature rupture of membranes at 35 weeks of gestation. She develops fever up to 103°F, and the amniotic fluid reveals a group B Streptococcus. Which of the following is the best option to reduce Group B streptococcal infection in her fetus?


a. Identification of possible high-risk births


b. Intravenous penicillin administered at least 4 hours before delivery


c. Screening of pregnant female at the first office visit, usually during the first trimester


d. Screening of pregnant female in the last trimester


e. Use of a polysaccharide vaccine


208. A 1-week-old neonate presents to the pediatric emergency room with fever, irritability, poor feeding, and a bulging anterior fontanelle. Lumbar puncture is performed, and the cerebrospinal fluid (CSF) grows group B Streptococcus. Which of the following is the most likely pathogenic mechanism?


a. Complement C5a, a potent chemoattractant, activates polymorphonuclear neutrophils (PMNs)


b. In the absence of a specific antibody, opsonization, phagocyte recognition, and killing do not proceed normally


c. The alternative complement pathway is activated


d. The streptococci are resistant to penicillin


209. A man who has a penile chancre appears in a hospital’s emergency service. The VDRL test is negative. Which of the following is the most appropriate course of action?


a. Perform dark-field microscopy for treponemes


b. Perform a Gram stain on the chancre fluid


c. Repeat the VDRL test in 10 days


d. Send the patient home untreated


e. Swab the chancre and culture on Thayer-Martin (TM) agar


210. A clinically depressed farmer complains of extreme weakness, a daily rise and fall in fever, and night sweats. Small gram-negative rods are isolated from blood cultures after a 2-week incubation period. Which of the following organisms is the most likely etiologic agent?


a. Brucella melitensis


b. Campylobacter jejuni


c. Francisella tularensis


d. Salmonella enteritidis


e. Serratia marcescens


211. An outbreak occurs in a community where the water supply is contaminated. Multiple patients experience nausea and vomiting as well as profuse diarrhea with abdominal cramps; stools are described as “rice water.” Curved, gram-negative rods are isolated on a sulfate-citrate-bile-sucrose agar. In the treatment of patients who have cholera, the use of a drug that inhibits adenyl cyclase would be expected to have which of the following characteristics?


a. Block the action of cholera toxin


b. Eradicate the organism


c. Increase fluid secretion


d. Kill the patient immediately


e. Reduce intestinal motility


212. A box of ham sandwiches with mayonnaise, prepared by a person with a boil on his neck, is left out of the refrigerator for the on-call interns. Three doctors become violently ill approximately 2 hours after eating the sandwiches. Which of the following is the most likely cause?


a. Clostridium perfringens toxin


b. Coagulase from S. aureus in the ham


c. Penicillinase given to inactivate penicillin in the pork


d. Staphylococcus aureus enterotoxin


e. Staphylococcus aureus leukocidin


213. A 34-year-old diabetic truck driver notices maceration of the web space of his toes on the right foot. Two days later he has a temperature of up to 100°F, exquisite tenderness, erythema, and swelling of the right leg. Culture exudate from the foot yields S. aureus. Which of the following often complicates treatment of S. aureus infection with penicillin?


a. Allergic reaction caused by staphylococcal protein


b. Inability of penicillin to penetrate the membrane of S. aureus


c. Lack of penicillin-binding sites on S. aureus


d. Production of penicillin acetylase by S. aureus


e. Production of penicillinase by S. aureus


214. Two of 3 family members have dinner at a local restaurant and, within 48 hours, start experiencing double vision, difficulty in swallowing and speaking, and breathing problems. These symptoms are consistent with which of the following?


a. Activation of cyclic AMP


b. Endotoxin shock


c. Ingestion of a neurotoxin


d. Invasion of the gut epithelium by an organism


e. Secretion of an enterotoxin


215. A clinical research group attempting to develop an improved Neisseria meningitidis vaccine is granted approval to gather volunteers for a clinical trial. Part of the volunteer evaluation is to sample bacteriologically for normal oral flora Neisseria. They find that almost all of the participants have several commensal species as part of their upper respiratory tract (URT) flora. Which of the following statements accurately describes the significance of these bacteria?


a. As a part of the normal flora, Neisseria provide a natural immunity in local host defense


b. As a part of the respiratory flora, they are the most common cause of acute bronchitis and pneumonia


c. Commensal bacteria stimulate a cell-mediated immunity (CMI)


d. Commensal Neisseria in the upper respiratory tract impede phagocytosis by means of lipoteichoic acid


e. Normal flora, such as nonpathogenic Neisseria, provides effective nonspecific B-cell-mediated humoral immunity


216. A family routinely consumes unpasteurized milk, claiming “better taste.” Several members experience a sudden onset of crampy abdominal pain, fever, and profuse bloody diarrhea. Campylobacter jejuni is isolated and identified from all patients. Which of the following is the treatment of choice for this type of enterocolitis?


a. Ampicillin


b. Campylobacter antitoxin


c. Ciprofloxacin


d. Erythromycin


e. Pepto-Bismol


217. An unimmunized, 2-year-old boy presents with drooling from the mouth, elevated temperature, and enlarged tonsils. During attempts at intubation, no gray-white membrane is observed but the epiglottis appears “beefy” red and edematous. Which of the following is the most likely organism?


a. Haemophilus haemolyticus


b. Haemophilus influenzae


c. Klebsiella pneumoniae


d. Mycoplasma pneumoniae


e. Neisseria meningitidis


Questions 218 to 220


218. A 70-year-old female patient is readmitted to a local hospital with fever and chills following cardiac surgery at a major teaching institution. A gram-positive coccus grows within 24 hours from blood taken from the patient. Initial tests indicate that this isolate is resistant to penicillin. Which of the following is the most likely identification?


a. Enterococcus species


b. Group A Streptococcus


c. Group B Streptococcus


d. Neisseria species


e. Streptococcus pneumoniae


219. Further testing of the patient in the previous question reveals that the isolate possesses the group D antigen, and is not β-lactamase-positive, but is resistant to vancomycin. Which of the following is the most likely identification of this isolate?


a. Enterococcus casseliflavus


b. Enterococcus durans


c. Enterococcus faecalis


d. Enterococcus faecium


e. Streptococcus pneumoniae


220. Which of the following is the treatment of choice for the isolate in Question 219?


a. Ciprofloxacin


b. Gentamicin


c. Gentamicin and ampicillin


d. Rifampin


e. No available treatment


221. A young man crashes his bicycle, injuring one leg. Bacteria from the wound and a subsequent blood culture are isolated and identified, and an acute hematogenous osteomyelitis is diagnosed. Which organism listed below most often causes this type of infection?


a. Escherichia coli


b. Proteus mirabilis


c. Staphylococcus aureus


d. Staphylococcus epidermidis


e. Streptococcus faecalis


222. A 3-year-old girl, with no history of vaccination, is brought to the hospital with a sore throat, fever, malaise, and difficulty in breathing. Physical examination reveals a gray membrane covering the pharynx. Growth of the etiologic agent on cysteine-tellurite agar forms gray-to-black colonies with a brown halo. The major virulence factor of this organism is only produced by those strains that will most likely have which of the following characteristics?


a. Encapsulated


b. Endotoxin


c. Glucose fermenters


d. Lysogenic for β-prophage


e. Sucrose fermenters


Questions 223 to 225


A 28-year-old menstruating woman appears in the emergency room with the following signs and symptoms: fever, 104°F (40°C); WBC, 16,000/μL; blood pressure, 90/65 mm Hg; a scarlatiniform rash on her trunk, palms, and soles; extreme fatigue; vomiting; and diarrhea.


223. Which of the following is the most likely diagnosis?


a. Chicken pox


b. Guillain–Barré syndrome


c. Scalded skin syndrome


d. Staphylococcal food poisoning


e. Toxic shock syndrome (TSS)


224. Culture of the menstrual fluid in this case cited would most likely reveal a predominance of which of the following?


a. Clostridium difficile


b. Clostridium perfringens


c. Gardnerella vaginalis


d. Staphylococcus aureus


e. No organisms isolated


225. Which of the following is the most likely source and characteristic finding not yet revealed in the case just presented?


a. A meal of chicken in a fast-food restaurant


b. A retained tampon


c. Heavy menstrual flow


d. Recent exposure to rubella


e. Travel to Vermont


Questions 226 and 227


A severe URT outbreak occurs in the residence of students of a private school, resulting in several cases of otitis media and acute sinusitis. Some students do not have any clinical evidence of infection. The state public health laboratory receives and evaluates a new LA reagent for H. influenzae polysaccharide capsular antigen in urine (intact antigen elimination). The results, shown below, are compared with the isolation of H. influenzae from pharyngeal swabs.


LA POS, CULT POS: 25


LA POS, CULT NEG: 5


LA NEG, CULT POS: 5


LA NEG, CULT NEG: 95


226. Which of the following best indicates the sensitivity of LA?


a. 0%


b. 30%


c. 85%


d. 95%


e. 100%


227. Which of the following best indicates the specificity of LA?


a. 0%


b. 30%


c. 80%


d. 95%


e. 100%


228. A severely burned firefighter develops a rapidly disseminating bacterial infection while hospitalized. “Green pus” is noted in the burned tissue, and cultures of both the tissue and blood yield small, oxidase-positive, gram-negative rods. Which of the following statements best describes this organism?


a. Endotoxin is the only virulence factor known to be produced by these bacteria


b. Humans are the only known reservoir hosts for these bacteria


c. The bacteria are difficult to culture because they have numerous growth requirements


d. These are among the most antibiotic resistant of all clinically relevant bacteria


e. These highly motile bacteria can “swarm” over the surface of culture media


229. Several hours after dining on sweet and sour chicken and pork fried rice at the home of an Asian friend, a 34-year-old car salesman exhibits abdominal discomfort, nausea, and vomiting. In the middle of the night he awakens with watery diarrhea. Which of the following pairs of organisms is routinely responsible for food poisoning?


a. Clostridium botulinum and Bacillus anthracis


b. Clostridium difficile and C. botulinum


c. Clostridium perfringens and B. cereus


d. Clostridium tetani and B. anthracis


e. Clostridium tetani and B. cereus


230. MRSA is isolated from seven patients in a 14-bed intensive care unit. All patients are isolated and the unit closed to any more admissions. Which of the following best explains these rigorous methods to control MRSA?


a. MRSA causes TSS


b. MRSA is inherently more virulent than other staphylococci


c. MRSA is resistant to penicillin


d. MRSA spreads more rapidly from patient to patient than antibiotic-susceptible staphylococci do


e. The alternative for treatment of MRSA is vancomycin, an expensive and potentially toxic antibiotic


231. A 2-year-old infant is brought to the emergency room with hematuria, fever, and thrombocytopenia. Which one of the following bacteria would most likely be isolated from a stool specimen?


a. Aeromonas species


b. Enterobacter aerogenes


c. Escherichia coli 0157/H7


d. Salmonella enteritidis


e. Shigella flexneri


232. A 65-year-old healthy, retired female executive goes to Mexico on her yearly vacation. Unlike her previous trips, she decides to use the local water to make her favorite punch. Thirty-six hours later, she develops profuse watery diarrhea, severe cramping, and abdominal pain. She is diagnosed with Escherichia coli-related diarrhea. Which of the following E. coli types is characterized by the presence of heat-labile (LT) and heat-stable (ST) toxin proteins?


a. Enteroinvasive (EIEC)


b. Enterotoxigenic (ETEC)


c. Enterohemorrhagic (EHEC)


d. Enteropathogenic (EPEC)


233. A 48-year-old farmer in New Mexico is bitten by a flea and, 5 days later, develops a sudden onset of fever, chills, weakness, and headache. A few hours later he develops swollen, necrotic lymph nodes (buboes) in the right axilla and groin, which are intensely painful. This patient is subsequently diagnosed with bubonic plague and does not develop any pneumonic features of the disease. Human plague can be bubonic or pneumonic. Which of the following is the primary epidemiologic difference between the two clinical forms of plague?


a. Age of the patient


b. Geographic location of the animal vector


c. Health of the animal vector


d. Route of infection


e. Season of the year


234. A 9-year-old child is brought to the emergency room with the chief complaint of enlarged, painful axillary lymph nodes. The resident physician also notes a small, inflamed, dime-sized lesion surrounding what appears to be a small scratch on the forearm. The lymph node is aspirated and some pus is sent to the laboratory for examination. A Warthin-Starry silver impregnation stain reveals many highly pleomorphic, rod-shaped bacteria. Which of the following is the most likely cause of this infection?


a. Bartonella henselae


b. Brucella canis


c. Mycobacterium scrofulaceum


d. Yersinia enterocolitica


e. Yersinia pestis


235. A sixth-grade boy returns from a summer camp with several minor cuts and abrasions. Within a week, extensive cellulitis develops, and it is apparent that subcutaneous tissue is involved, requiring surgical removal of nonviable tissue. Antibiotics are used aggressively. Cellulitis is usually caused by which of the following?


a. Bacillus cereus


b. Clostridium tetani


c. Group A streptococci


d. Micrococcus species


e. Staphylococcus aureus


236. A 40-year-old female reports chronic gastritis. She tests positive for H. pylori. After a course of the appropriate antibiotic therapy, her symptoms subside. Which of the following is the most effective noninvasive test for the diagnosis of Helicobacter-associated gastric ulcers?


a. Culture of stomach contents for H. pylori


b. Detection of H. pylori antigen in stool


c. Growth of H. pylori from a stomach biopsy


d. Growth of H. pylori in the stool


e. IgM antibodies to H. pylori


237. The following examination and test results are observed in a woman tested in November who reports being in the woods in Pennsylvania during the last summer. While there, she was bitten by a tick, and now has a flattened red area near the bite with central clearing. She also has flu-like illness with fever, myalgia, and headache. Which of the following is the most appropriate course of action?


a. Ask the patient if she has a severe headache


b. Do a spinal tap for CSF


c. Observe the lesion


d. Order a Lyme disease antibody titer


e. Start treatment with tetracycline


238. Several white male patients, over 50 years of age and suffering from cavitary pulmonary disease, being followed and treated at a university AIDS clinic are found to be infected by Mycobacterium avium, a major opportunist pathogen. M. avium from these patients is best characterized by which one of the following statements?


a. Few isolates from AIDS patients are acid-fast.


b. Most isolates from AIDS patients are sensitive to isoniazid and streptomycin


c. M. avium can be isolated from the blood of many AIDS patients


d. M. avium isolates from AIDS patients are of multiple serovars


e. The majority of M. avium isolates from AIDS patients are nonpigmented


239. A 12-year-old girl experiences a group A streptococcus pharyngitis and, within 3 weeks, has chest pain and develops new murmurs of mitral regurgitation. Which of the following statements best typifies the disease she is suffering from?


a. It is a complication of group A streptococcal skin disease but usually not of pharyngitis


b. It is characterized by inflammatory lesions that may involve the heart, joints, subcutaneous tissues, and CNS


c. It is very common in developing countries but extremely rare and decreasing in incidence in the United States


d. Prophylaxis with benzathine penicillin is of little value


e. The pathogenesis is related to the similarity between a staphylococcal antigen and a human cardiac antigen


240. After extraction of a wisdom tooth, an 18-year-old male student is diagnosed with subacute bacterial endocarditis (SBE). He has a congenital heart disease that has been under control. Which of the following is the most likely organism causing the infection?


a. Staphylococcus aureus


b. Staphylococcus epidermidis


c. Streptococcus pneumoniae


d. Streptococcus viridans


e. Enterococcus faecalis


241. A 70-year-old male is taken to the emergency room with a history of “cold-like” symptoms for at least 3 days. At the time of the visit, his temperature is 102°F and he experienced shaking, chills, chest pain, and a productive cough with bloody sputum. Blood agar culture reveals gram-positive α-hemolytic colonies. If a quellung test was done on the colonies, which of the following bacteria would most likely be positive?


a. Corynebacterium diphtheriae


b. Enterobacter species


c. Haemophilus parainfluenzae


d. Neisseria gonorrhoeae


e. Streptococcus pneumoniae


242. A 6-month-old infant is admitted to the hospital with acute meningitis. The Gram stain reveals gram-positive, short rods, and the mother indicates that the child has received “all” of the meningitis vaccinations. Which of the following is the most likely cause of the disease?


a. Haemophilus influenzae


b. Listeria monocytogenes


c. Neisseria meningitidis, group A


d. Neisseria meningitidis, group C


e. Streptococcus pneumoniae


243. A 40-year-old man presents to the emergency medicine department 1 week following a foot injury. He is experiencing intense pain in the area of injury and the muscles of the jaw. Which of the following is the most common portal of entry for the etiologic organism?


a. Gastrointestinal (GI) tract


b. Genital tract


c. Nasal tract


d. Respiratory tract


e. Skin


244. A 22-year-old homeless person with a known drug abuse problem and multiple opportunistic infections has a positive PPD (purified protein) test. Which of the following is the most common way this infection is acquired?


a. GI tract


b. Genital tract


c. Nasal tract


d. Respiratory tract


e. Skin


245. A 31-year-old school teacher returns from foreign travel and experiences a sudden (1-2 days) onset of abdominal pain, fever, and watery diarrhea, caused by a heat-labile exotoxin that affects both the gut and the CNS. This infection is caused by an etiologic agent commonly acquired through which of the following routes?


a. GI tract


b. Genital tract


c. Nasal tract


d. Respiratory tract


e. Skin


246. A college student is surprised one morning by painful urination and a cream-colored exudate. Any person who acquires the gram-negative microbe that causes this infection is most likely to have acquired it via which of the following?


a. GI tract


b. Genitourinary tract


c. Nasal tract


d. Respiratory tract


e. Skin


247. A 25-year-old college student with no history of allergic rhinitis has a 12-day history of facial pain, clear rhinorrhea, fever, headache, and back pain. Her symptoms do not respond to over-the-counter medication. Culture of the fluid from the sinus reveals Moraxella (Branhamella) catarrhalis. Which of the following best characterizes M. catarrhalis?


a. A gram-negative, pleomorphic rod that can cause endocarditis


b. A gram-negative rod, fusiform-shaped, that is associated with periodontal disease but may cause sepsis


c. The causative agent of rat-bite fever


d. The gram-negative diplococcus, which is the causative agent of sinusitis, bronchitis, and pneumonia


e. The causative agent of trench fever


248. A 16-year-old Hispanic female with poor oral hygiene and severe gingivitis presents with a temperature of 103.5°F and hypotension. Blood culture is positive for Capnocytophaga. Which of the following best characterizes Capnocytophaga?


a. A gram-negative, pleomorphic rod that can cause endocarditis


b. A gram-negative rod, fusiform-shaped, that is associated with periodontal disease but may cause sepsis


c. The causative agent of rat-bite fever


d. The causative agent of sinusitis, bronchitis, and pneumonia


e. The causative agent of trench fever


249. Several employees in a veterinary facility experience a mild influenza-like infection after working on six sheep with an undiagnosed illness. The etiologic agent causing the human disease is most often transmitted to humans by which of the following methods?


a. Fecal contamination from flea deposits on the skin


b. Inhalation of infected particles or aerosols from the suspected animal urine and feces


c. Lice feces scratched into the broken skin during the louse’s blood feeding


d. Tick saliva during feeding on human blood


e. Urethral discharge from infected humans


250. An endocarditis patient under a physician’s care develops a urinary tract infection (UTI). A group D enterococcus (Enterococcus faecium) is isolated but the UTI does not respond to ampicillin and gentamicin treatments. Which of the following options would be considered the most clinically appropriate action?


a. Consider vancomycin as an alternative drug


b. Determine if fluorescent microscopy is available for the diagnosis of actinomycosis


c. Do no further clinical workup


d. Suggest to the laboratory that low colony counts may reflect infection


e. Suggest a repeat antibiotic susceptibility test


251. A patient with symptoms of a UTI has a culture taken, which grows 5 × 103 E. coli. The laboratory reports it as “insignificant.” Which of the following is the most appropriate next step in management?


a. Consider vancomycin as an alternative drug


b. Determine if fluorescent microscopy is available for the diagnosis of actinomycosis


c. Do no further clinical workup


d. Suggest to the laboratory that low colony counts may reflect infection; follow up with culture


e. Suggest a repeat antibiotic susceptibility test


252. A patient appears in the emergency room with a submandibular mass. A smear is made of the drainage and a bewildering variety of bacteria are seen, including branched, gram-positive rods. Which of the following is the most clinically appropriate action?


a. Consider vancomycin as an alternative drug


b. Determine if fluorescent microscopy is available for the diagnosis of actinomycosis


c. Do no further clinical workup


d. Suggest to the laboratory that low colony counts may reflect infection


e. Suggest a repeat antibiotic susceptibility test


253. A 55-year-old male develops malaise, fever up to 103.5°F, nonproductive cough, headache, and shortness of breath a few days after he repaired the cooling system of an old hotel. A chest x-ray reveals fluid in his lungs. From a sputum sample, a gram-negative rod grew slowly on a buffered cysteine containing charcoal-yeast agar. Which of the following antibiotic therapies is most appropriate for treating this patient?


a. Ampicillin


b. Ceftriaxone


c. Erythromycin


d. Penicillin


e. Vancomycin


254. A 60-year-old male resident from a nursing home presents to the emergency room with a fever of 105.8°F (41°C), shaking chills, severe pain to the right side of his chest that worsens with breathing, and a productive cough with blood-tinged sputum. During the previous 3 days, he noted cold-like symptoms. Gram stain evaluation of the sputum reveals gram-positive diplococci that grow into α-hemolytic colonies on blood agar. Which of the following antibiotic therapies is the most appropriate treatment for this patient?


a. Ampicillin


b. Ceftriaxone


c. Erythromycin


d. Penicillin


e. Vancomycin


255. A 12-year-old boy, after a camping trip near a wooded area in Northern California, is taken to the emergency room after complaining of a headache. He has an erythema migrans rash around what appears to be a tick bite. Which of the following is the antibiotic of choice for treating this patient?


a. Ampicillin


b. Ceftriaxone


c. Erythromycin


d. Penicillin


e. Vancomycin


256. A 6-year-old girl presents to her pediatrician with fever, headache, and a sore throat. She has swollen, tender cervical lymph nodes, and her oropharynx is red with a gray-white exudate covering both her tonsils. A rapid strep test of her throat swab is positive, and the culture subsequently grows β-hemolytic Streptococcus. Which of the following antibiotic therapies is most appropriate for treating this patient?


a. Ampicillin


b. Ceftriaxone


c. Erythromycin


d. Penicillin


e. Vancomycin


257. A young woman being treated with a broad-spectrum antimicrobial develops endoscopically observed microabscesses and diarrhea. Which of the following is the therapy of choice for this form of enterocolitis?


a. Ampicillin


b. Ceftriaxone


c. Erythromycin


d. Penicillin


e. Vancomycin


258. Although cholera, a Vibrio infection, has rarely been seen in the United States, there have been recent outbreaks of classic cholera associated with shellfish harvested from the Gulf of Mexico. Vibrios are shaped like curved rods, and infections more common than cholera may be caused by a variety of curved-rod bacteria. Which of the following best describes C. jejuni?


a. Cause of gastroenteritis; reservoir in birds and mammals, optimal growth at 107.6°F (42°C)


b. Human pathogen, halophilic, lactose-negative, sucrose-negative; causes GI diseases primarily from ingestion of under-cooked seafood


c. Human pathogen, halophilic, lactose-positive; produces heat-labile, extracellular toxin wound infections


d. Organisms are susceptible to acid; not an invasive organism


e. Urease-positive; cause of fetal distress in cattle


259. Vibrio cholerae is worldwide in distribution and continues to expand as water sources become polluted. Which of the following best describes this organism?


a. Cause of gastroenteritis; reservoir in birds and mammals, optimal growth at 107.6°F (42°C)


b. Human pathogen, halophilic, lactose-negative, sucrose-negative; causes GI diseases primarily from ingestion of under-cooked seafood


c. Human pathogen, halophilic, lactose-positive; produces heat-labile, extracellular toxin, wound infections


d. Organisms susceptible to acid; not an invasive organism


e. Urease-positive; cause of fetal distress in cattle


260. A 20-year-old female in post-Katrina New Orleans eats poorly cooked seafood (oysters, clams, and mollusks) for her birthday dinner. Twenty-four hours later, she develops explosive watery diarrhea and abdominal cramps. She is positive for V. parahaemolyticus. Which of the following best describes this organism?


a. Cause of gastroenteritis; reservoir in birds and mammals, optimal growth at 107.6°F (42°C)


b. Human pathogen, halophilic, lactose-negative, sucrose-negative; causes GI diseases primarily from ingestion of under-cooked seafood


c. Human pathogen, halophilic, lactose-positive; produces heat-labile, extracellular toxin, wound infections


d. Organisms susceptible to acid; not an invasive organism


e. Urease-positive; cause of fetal distress in cattle


261. A 25-year-old male, with a history of hepatitis C, has to wade through brackish water in post-Katrina New Orleans. He develops worsening abdominal pain and jaundice. Regarding Vibrio vulnificus, which of the following best describes this organism?


a. Cause of gastroenteritis; reservoir in birds and mammals, optimal growth at 107.6°F (42°C)


b. Human pathogen, halophilic, lactose-negative, sucrose-negative; causes GI diseases primarily from ingestion of under-cooked seafood


c. Human pathogen, halophilic, lactose-positive; produces heat-labile, extracellular toxin, wound infections


d. Organisms susceptible to acids; not an invasive organism


e. Urease-positive; cause of fetal distress in cattle


262. Yersinia enterocolitica, formerly a Pasteurella, has more than 50 sero-types that can be isolated from rodents, sheep, cattle, swine, dogs, and cats and water contaminated by them, and is best described by which of the following?


a. Commonly inhabits the canine respiratory tract and is an occasional pathogen for humans; strongly urease-positive


b. Gram-negative bipolar stained bacilli that cause diarrhea by means of a heat-stable enterotoxin, with abdominal pain that may be mistaken for appendicitis


c. Pits agar, grows both in carbon dioxide and under anaerobic conditions, and is part of the normal oral cavity flora


d. Typically infects cattle, requires 5% to 10% carbon dioxide for growth, and is inhibited by the dye thionine


e. Typically is found in infected animal bites in humans and can cause hemorrhagic septicemia in animals


263. Four weeks after assisting in several calf deliveries, a farmer develops fever, weakness, muscle aches, and sweats. The fever rises in the afternoon and falls during the night. Brucella abortus is isolated. Which one of the three Brucella species is a possible bioterrorism agent and is best described by one of the following?


a. Commonly inhabits the canine respiratory tract and is an occasional pathogen for humans; strongly urease-positive


b. Gram-negative bipolar stained bacilli that cause diarrhea by means of a heat-stable enterotoxin, with abdominal pain that may be mistaken for appendicitis


c. Pits agar grows both in carbon dioxide and under anaerobic conditions, and is part of the normal oral cavity flora


d. Typically infects cattle, requires 5% to 10% carbon dioxide for growth, and is inhibited by the dye thionine


e. Typically is found in infected animal bites in humans and can cause hemorrhagic septicemia in animals


264. Bordetella bronchiseptica could be confused with the agent of whooping cough since it occasionally causes chronic respiratory tract infections in humans, but has less intensive symptoms (rhinitis and cough). It is best described by which of the following?


a. Commonly inhabits the canine respiratory tract and is an occasional pathogen for humans; strongly urease-positive


b. Gram-negative bipolar stained bacilli that cause diarrhea by means of a heat-stable enterotoxin, with abdominal pain that may be mistaken for appendicitis


c. Pits agar grows both in carbon dioxide and under anaerobic conditions, and is part of the normal oral cavity flora


d. Typically infects cattle, requires 5% to 10% carbon dioxide for growth, and is inhibited by the dye thionine


e. Typically is found in infected animal bites in humans and can cause hemorrhagic septicemia in animals


265. Pasteurella species can produce a range of human diseases and formerly included all yersiniae and francisellae organisms. Pasteurella multocida occurs worldwide in the URT and GI tracts of domestic and wild animals. It is best described by which of the following?


a. Commonly inhabits the canine respiratory tract and is an occasional pathogen for humans; strongly urease-positive


b. Gram-negative bipolar stained bacilli that cause diarrhea by means of a heat-stable enterotoxin, with abdominal pain that may be mistaken for appendicitis


c. Pits agar grows both in carbon dioxide and under anaerobic conditions, and is part of the normal oral cavity flora


d. Typically infects cattle, requires 5% to 10% carbon dioxide for growth, and is inhibited by the dye thionine


e. Typically is found in infected animal bites in humans and can cause hemorrhagic septicemia in animals


266. A 26-year-old male presents to his family physician with complaints of painful burning during urination and a milky discharge. The purulent discharge reveals many neutrophils with intracellular gram-negative diplococci. Which of the following mediums would most likely be used for isolating Neisseria gonorrhoeae, the suspected organism?


a. Löffler medium


b. Löwenstein–Jensen medium


c. Sheep blood agar


d. TM agar


e. Thiosulfate citrate bile salts sucrose medium


267. Twenty-four hours after returning from a short trip to Asia, a 35-year-old female has a sudden onset of vomiting and massive watery diarrhea that is colorless, odorless, and contains flecks of mucus. Which of the following mediums would most likely be used for isolating V. cholerae, the suspected organism?


a. Löffler medium


b. Löwenstein–Jensen medium


c. Sheep blood agar


d. TM agar


e. Thiosulfate citrate bile salts sucrose medium


268. A 32-year-old female prostitute is seen at the public health clinic with fever, night sweats, and reports coughing up blood. Her medical history reveals that she is HIV positive and has lost 20 lbs over the past month. Acid-fast bacilli are observed in the sputum. After digestion of the sputum, isolation of the suspected organism is best accomplished by using which one of the following media?


a. Löffler medium


b. Löwenstein–Jensen medium


c. Sheep blood agar


d. TM agar


e. Thiosulfate citrate bile salts sucrose medium


269. Bacillus and Clostridium species are spore-forming bacilli and can survive in the environment for years. Several species cause important disease in humans, although most will respond quickly to appropriate antibiotic therapy. However, which organism listed below would not benefit from such prompt antibiotic treatment?


a. Bacillus anthracis


b. Clostridium botulinum


c. Clostridium difficile


d. Clostridium perfringens


e. Clostridium tetani


270. A 12-year-old boy has sudden onset of fever, headache, and stiff neck. Two days earlier, he swam in a lake that is believed to have been contaminated with dog excreta. Leptospirosis is suspected. Which of the following laboratory tests is most appropriate to determine whether he has been infected with leptospira?


a. Agglutination test for leptospiral antigen


b. Counterimmunoelectrophoresis of urine sample


c. Gram stain of urine specimen


d. Spinal fluid for dark-field microscopy and culture in Fletcher serum medium


e. Urine culture on EMB and TM agar


271. A 60-year-old female complains of tenderness and pain around a peritoneal catheter. Blood cultures reveal gram-positive, catalase-positive cocci. Which of the following is the most likely organism that is also considered a predominant organism on skin?


a. α-Hemolytic streptococci


b. Bacteroides fragilis


c. Escherichia coli


d. Lactobacillus species


e. Staphylococcus epidermidis


272. A healthy 45-year-old female had root canal treatment about 3 weeks ago. She now presents with a new heart murmur, fever, painful skin nodules, abdominal pain, and an abnormal liver function test. Which of the following organisms would mostly likely cause endocarditis and is implicated in dental caries or root canal infections?


a. α-Hemolytic streptococci


b. Bacteroides fragilis


c. Escherichia coli


d. Lactobacillus species


e. Staphylococcus epidermidis


273. A 17-year-old man is hospitalized with trauma to the abdomen following a gang-related fight. He develops an intraabdominal abscess, which is drained and sent to the laboratory. A mixture of gram-negative anaerobes is detected. Which of the following microorganisms is the most likely and is also the most prevalent bacterium in the gut?


a. α-Hemolytic streptococci


b. Bacteroides fragilis


c. Escherichia coli


d. Lactobacillus species


e. Staphylococcus epidermidis


274. A 25-year-old female is treated with a course of broad-spectrum antibiotics for severe pelvic inflammatory disease. She now reports a thick milky white pruritic vaginal discharge. Which of the following is the most prevalent microorganism in the vagina and may also be protective?


a. α-Hemolytic streptococci


b. Bacteroides fragilis


c. Escherichia coli


d. Lactobacillus species


e. Staphylococcus epidermidis


275. Viridans streptococci (S. mutans, S. mitis) usually have α-hemolysis and are optochin-resistant. They are becoming increasingly important as causes of endocarditis and abscesses (mixed infections). Which of the following best describes S. mutans?


a. An anaerobic, filamentous bacterium that often causes cervicofacial osteomyelitis


b. A β-hemolytic organism that causes a diffuse, rapidly spreading cellulitis


c. A facultative anaerobe that is highly cariogenic and sticks to teeth by synthesis of a dextran


d. A facultative anaerobe that often inhabits the buccal mucosa early in a neonate’s life and can cause bacterial rheumatic fever (RF)


e. A facultatively anaerobic, rod-shaped bacterium that sticks to teeth and is cariogenic, commonly involved in problems involving dental procedures, trauma, surgery, or aspiration


276. Streptococcus salivarius, a common isolate, which is considered as normal, nonpathogenic flora in the clinical laboratory, is best described by which of the following?


a. An anaerobic, filamentous bacterium that often causes cervicofacial osteomyelitis


b. A β-hemolytic organism that causes a diffuse, rapidly spreading cellulitis


c. A facultative anaerobe that is highly cariogenic and sticks to teeth by synthesis of a dextran


d. A facultative anaerobe that often inhabits the buccal mucosa early in a neonate’s life and can cause bacterial RF


e. A facultatively anaerobic, rod-shaped bacterium that sticks to teeth and is cariogenic, commonly involved in problems involving dental procedures, trauma, surgery, or aspiration


277. Actinomyces species are a large, diverse group of gram-positive bacilli. Actinomyces israelii is an organism that causes pyogenic lesions with interconnecting sinus tracts that contain granules of microcolonies embedded in the tissues. It is best described by which of the following?


a. An anaerobic, filamentous bacterium that often causes cervicofacial osteomyelitis


b. A β-hemolytic organism that causes a diffuse, rapidly spreading cellulitis


c. A facultative anaerobe that is highly cariogenic and sticks to teeth by synthesis of a dextran


d. A facultative anaerobe that often inhabits the buccal mucosa early in a neonate’s life and can cause bacterial RF


e. A facultatively anaerobic, rod-shaped bacterium that sticks to teeth and is cariogenic, commonly involved in problems involving dental procedures, trauma, surgery, or aspiration


278. Actinomyces viscosus, a ubiquitous actinomycete, grows under micro-aerophilic or strict anaerobic conditions and produces a yellow-orange granule in the typical tissue exudates. It is best described by which of the following?


a. An anaerobic, filamentous bacterium that often causes cervicofacial osteomyelitis


b. A β-hemolytic organism that causes a diffuse, rapidly spreading cellulitis


c. A facultative anaerobe that is highly cariogenic and sticks to teeth by synthesis of a dextran


d. A facultative anaerobe that often inhabits the buccal mucosa early in a neonate’s life and can cause bacterial RF


e. A facultatively anaerobic, rod-shaped bacterium that sticks to teeth and is cariogenic, commonly involved in problems involving dental procedures, trauma to or surgery of the oral cavity, or aspiration


279. A 3-year-old girl from a family that does not believe in immunization presents to the emergency room with a sore throat, fever, malaise, and difficulty breathing. A gray membrane covering the pharynx is observed on physical examination. Which of the following best describes C. diphtheriae, the etiologic agent?


a. It produces at least one protein toxin consisting of two subunits, A and B, that cause severe spasmodic cough, usually in children


b. It produces a toxin that blocks protein synthesis in an infected cell and carries a lytic bacteriophage that produces the genetic information for toxin production


c. It secretes an erythrogenic toxin that causes the characteristic signs of scarlet fever


d. It secretes an exotoxin that has been called “verotoxin” and “Shiga-like toxin”; infection is mediated by specific attachment to mucosal membranes


e. It requires cysteine for growth


280. A 4-year-old boy is taken to see his pediatrician because of a persistent cough that gradually worsened over a 12-day period. On the day of the examination, the cough is so severe that it is frequently followed by vomiting. A blood cell count shows marked leukocytosis with a predominance of lymphocytes. Which of the following best characterizes this microorganism?


a. It produces a toxin that increases cAMP levels, resulting in increased mucus production


b. It produces a toxin that blocks protein synthesis in an infected cell and carries a lytic bacteriophage that produces the genetic information for toxin production


c. It secretes an erythrogenic toxin that causes the characteristic signs of scarlet fever


d. It secretes an exotoxin that has been called “verotoxin” and “Shiga-like toxin”; infection is mediated by specific attachment to mucosal membranes


e. It requires cysteine for growth


281. A 48-year-old deer hunter presents to the emergency room with lymphadenopathy and a skin lesion, which started as a painful papule at the site of a tick bite. The papule then ulcerates with a necrotic center and raised border. Aspirate of the ulcer is positive for F. tularensis. Which one of the following best characterizes this bacterium?


a. It produces at least one protein toxin consisting of two subunits, A and B, that cause severe spasmodic cough, usually in children


b. It produces a toxin that blocks protein synthesis in an infected cell and carries a lytic bacteriophage that produces the genetic information for toxin production


c. It secretes an erythrogenic toxin that causes the characteristic signs of scarlet fever


d. It secretes an exotoxin that has been called “verotoxin” and “Shiga-like toxin”; infection is mediated by specific attachment to mucosal membranes


e. It requires cysteine for growth


282. Ten boy scouts are hospitalized with bloody diarrhea and severe hematological abnormalities. An investigation establishes that all of the boys developed symptoms following consumption of hamburgers from the same fast-food restaurant chain. Which of the following best describes E. coli 0157/H7, the etiologic bacterium responsible for the outbreak?


a. It produces at least one protein toxin consisting of two subunits, A and B, that cause severe spasmodic cough, usually in children


b. It produces a toxin that blocks protein synthesis in an infected cell and carries a lytic bacteriophage that produces the genetic information for toxin production


c. It secretes an erythrogenic toxin that causes the characteristic signs of scarlet fever


d. It secretes an exotoxin that has been called “verotoxin” and “Shiga-like toxin”; infection is mediated by specific attachment to mucosal membranes


e. It requires cysteine for growth


283. A 4-year-old girl awakens at midnight complaining of a sore throat and headache, and she has a fever of 101°F. Physical examination reveals an erythematous throat. A rapid strep test is positive. A throat swab is sent to the laboratory for further testing. Which of the following best characterizes S. pyogenes as the presumed etiologic agent?


a. It produces at least one protein toxin consisting of two subunits, A and B, that cause severe spasmodic cough, usually in children


b. It produces a toxin that blocks protein synthesis in an infected cell and carries a lytic bacteriophage that produces the genetic information for toxin production


c. It secretes an erythrogenic toxin that causes the characteristic signs of scarlet fever


d. It secretes an exotoxin that has been called “verotoxin” and “Shiga-like toxin”; infection is mediated by specific attachment to mucosal membranes


e. It has capsules of polyglutamic acid, which is toxic when injected into rabbits


284. A 19-year-old military recruit who lives in the barracks develops a macular papular skin rash, severe headache, photophobia, fever, stiff neck, and blurred vision. He is presumed to have N. meningitidis. Which of the following is a characteristic physiological trait of this organism?


a. It causes spontaneous abortion and has tropism for placental tissue due to the presence of erythritol in allantoic and amniotic fluid


b. It has a capsule of polyglutamic acid, which is toxic when injected into rabbits


c. It possesses N-acetylneuraminic acid capsule and adheres to specific tissues by pili found on the bacterial cell surface


d. It secretes two toxins, A and B, in the large bowel during antibiotic therapy


e. It synthesizes protein toxin as a result of colonization of vaginal tampons


285. A 45-year-old cattle-farm worker goes to the public health clinic after experiencing 6 weeks of undulating fever, chills, sweating, headache, fatigue, muscle pain, and weight loss. History reveals that he enjoys drinking fresh unpasteurized milk with his other coworkers during the mid-morning breaks. A blood sample is sent to the state laboratory for serologic testing because the physician assistant suspects Brucella infection. Which of the following best characterizes this organism?


a. It causes spontaneous abortion and has tropism for placental tissue due to the presence of erythritol in allantoic and amniotic fluid


b. It has a capsule of polyglutamic acid, which is toxic when injected into rabbits


c. It has 82 polysaccharide capsular types; capsule is antiphagocytic; type 3 capsule (β-D-glucuronic acid polymer) most commonly seen in infected adults


d. It secretes two toxins, A and B, in the large bowel during antibiotic therapy


e. It synthesizes protein toxin as a result of colonization of vaginal tampons


286. An 18-year-old male patient presents to the emergency room with a 3-day history of fever, dry cough, difficulty in breathing, and muscle aches and pains. His chest x-ray shows a diffuse left upper lobe infiltrate. Mycoplasma pneumoniae pneumonia (walking pneumonia) may be rapidly identified by which of the following procedures?


a. Cold agglutinin test


b. Culture of respiratory secretions in HeLa cells after centrifugation of the inoculated tubes


c. Culture of respiratory secretions on monkey kidney cells


d. Detection of specific antigen in urine


e. Electron microscopy of sputum


287. A 50-year-old male presents with severe bilateral pulmonary infiltrate, elevated temperature leucocytosis, elevated enzymes, and elevated creatine kinase. He recently visited his favorite restaurant that had a large water fountain, which was misty on the day of his visit. Which of the following procedures would most rapidly diagnose the suspected organism that is the etiologic agent of Legionnaires disease in this patient?


a. Cold agglutinin test


b. Culture of respiratory secretions on a charcoal-based nutrient agar


c. Detection of antigen in respiratory secretions


d. Detection of specific antigen in urine


e. Electron microscopy of sputum


288. A group of elementary school-age children meet for a birthday party, and in the next few days, about half of them experience a mild upper respiratory illness, with sore throat and runny nose. One family gets laboratory work done and finds that Chlamydia pneumoniae (TWAR) is involved. Which of the following procedures would be best if the laboratory wanted to isolate this bacterium?


a. Cold agglutinin test


b. Culture of respiratory secretions in HeLa cells after centrifugation of the inoculated tubes


c. Culture of respiratory secretions on monkey kidney cells


d. Detection of specific antigen in urine


e. Electron microscopy of sputum


289. A 70-year-old man with a history of diabetes presents with severe pain in his right ear. The patient was diagnosed with external otitis. Further tests suggested that the patient suffered bone and nerve damage. Clinical laboratory analysis showed that the isolated microorganism produced a distinct blue pigment as well as an ADP-ribosylating toxin. What is the most likely causative agent?


a. Staphylococcus epidermidis


b. Staphylococcus aureus


c. Pseudomonas aeruginosa


d. Enterococcus faecalis


e. Candida albicans


290. A 40-year-old woman has a history of several months of gastric pain that was temporarily relieved with antacid. Stomach biopsies revealed the presence of comma-shaped organisms. The patient responded very well to a combined treatment of proton pump inhibitors and amoxicillin. Which of the following factors produced by the etiologic agent is associated with the development of gastric cancer in persons with chronic infections?


a. CagA protein


b. Flagella


c. Mucinase


d. Urease


e. Vacuolating toxin


291. A 60-year-old man suffered from fever, watery diarrhea, abdominal pain, and nausea. Three weeks later, he was admitted to the hospital unable to speak but coherent and oriented. Neurological examination revealed bilateral muscle weakness in his legs. Within hours, the muscle weakness extended to his arms and chest. He was diagnosed with Guillain–Barré syndrome. With which organism was he most likely infected?


a. Campylobacter jejuni


b. Clostridium tetani


c. Cytolmegalovirus


d. Salmonella enterica


e. Shigella sonnei


292. An outbreak of gastroenteritis occurred in a youth group camp. Water at the camp, which was not chlorinated or filtered, was obtained from a spring on the premises. The farmland near the camp was grazed by cattle and sheep. Run-off from the pasture entered the camp spring. The isolated microorganism required an atmosphere containing reduced oxygen and increased carbon dioxide for its growth. In most cases, the gastroenteritis was self-limiting. Those requiring antibiotic treatment responded to erythromycin. Which is the most likely causative agent?


a. Campylobacter jejuni


b. Enteroinvasive Escherichia coli (EIEC)


c. Enteropathogenic Escherichia coli (EPEC)


d. Vibrio cholerae


e. Vibrio parahaemolyticus


293. A man who had been wading while fishing in the Gulf of Mexico developed painful swellings that evolved into vesicles and bullae (image). These lesions became necrotic and the man developed septicemia, severe sepsis, and multiorgan dysfunction syndrome. Which of the following is the most likely cause of this man’s infection?


Image


(Reproduced, with permission, from Goldsmith LA, Katz SI, Gilchrest BA, et al. Fitzpatrick’s Dermatology in General Medicine. 8th ed. New York: McGraw-Hill Education; 2012. Fig. 183-4.)


a. Pseudomonas aeruginosa


b. Staphylococcus aureus


c. Streptococcus pyogenes


d. Vibrio parahaemolyticus


e. Vibrio vulnificus


294. A 60-year-old male in the intensive care unit recovering from back surgery required intubation for respiratory support. Forty-eight hours after intubation, he developed ventilator-associated pneumonia. The microorganism isolated from tracheal secretions aspirated from the patient is a gram-negative, oxidase positive, obligate aerobe that produces a multitude of virulence factors including proteases, toxins, and rhamnolipid. The patient was treated with broad-spectrum antibiotics for several weeks, but the treatment was unsuccessful and he died. Which is the most likely causative agent of this patient’s infection?


a. Escherichia coli


b. Haemophilus influenzae


c. Klebsiella pneumoniae


d. Moraxella catarrhalis


e. Pseudomonas aeruginosa


295. Four weeks after hurricane Rita, a 50-year-old man and his wife from southeastern Louisiana developed diarrhea. The man had mild diarrhea. However, his wife had severe watery diarrhea, fever, muscle cramps, and vomiting, which quickly progressed in to a loss of renal function and respiratory and cardiac failure. She responded very well to antibiotic and aggressive rehydration therapy. Stool samples from both patients contained gram-negative comma-shaped bacteria. Which is the most likely causative agent?


a. Campylobacter jejuni


b. Salmonella enterica


c. Shigella flexneri


d. Vibrio cholerae


e. Vibrio vulnificus


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Mar 17, 2017 | Posted by in MICROBIOLOGY | Comments Off on Bacteriology
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