B. The MIC is the amount of drug that can be administered in a single dose.

C. The MIC is the lowest drug level that is bacteriostatic.

D. The MIC is the lowest drug level that is nontoxic.

E. The MIC is the lowest drug level that kills the bacterial pathogen.

B. Legionella pneumophila.

C. Mycoplasma pneumonia.

D. Streptococcus pneumonia.

E. Staphylococcus aureus.

3. Gram-negative bacilli causing infections in health care settings often produce extended-spectrum β-lactamases (ESBLs). Which one type of the following antimicrobial agents is most appropriate for treating ESBL-producing pathogens?

B. Third-generation cephalosporins.

C. First-generation cephalosporins.

D. Second-generation cephalosporins.

E. Aztreonam.

B. Coagulase-negative staphylococci.

C. Streptococcus pneumoniae.

D. Staphylococci.

E. Enterococci.

5. A 70-year-old woman presents to her urologist with a urinary tract infection. Culture results indicate that the infecting pathogen is Escherichia coli, which has an MIC interpreted as “intermediate” for the antimicrobial agent of choice. Which one of the following statements best describes this MIC interpretation for this antibiotic?

B. This antibiotic may be efficacious either at higher doses or if concentrated in the urine.

C. Antibiotics with intermediate interpretations cannot be dosed at therapeutic levels.

D. An intermediate result indicates a technical error and must be repeated using the disk diffusion susceptibility method.

E. The intermediate category is interpreted as nonsusceptible.

6. The incidence and prevalence of etiologic agents causing sexually transmitted infections are underestimated due to diagnostic challenges and social stigma. Which one of the following statements regarding sexually transmitted infections is most accurate?

B. Nucleic acid amplification tests (NAATs) are the most sensitive and accurate method for detecting Neisseria gonorrhea and Chlamydia trachomatis infections.

C. Dark-field microscopic examination is used to diagnose herpes simplex ulcerative genital lesions.

D. Haemophilus ducreyi is the causative agent of lymphogranuloma venereum.

E. Syphilis is currently on the rise in the adolescent population in urban settings.

B. Chlamydia trachomatis.

C. Listeria monocytogenes.

D. Neisseria gonorrhoeae.

E. Campylobacter jejuni.

B. Haemophilus influenza.

C. Streptococcus pneumonia.

D. Neisseria meningitidis.

E. Listeria monocytogenes.

9. An 11-year-old patient presented to the emergency department with fever and axillary lymphadenopathy. Erythematous papules are noted on the right hand and forearm. A Gram stain and a Kinyoun acid-fast stain of a lymph node biopsy were both negative, as were cultures of the biopsy and blood cultures that were incubated for 5 days. The family has a 2-month-old kitten that they recently adopted from a shelter. The diagnosis was made using a serologic assay. Which one of the following is the most likely cause of the disease in this patient?

B. Borrelia burgdorferi.

C. Coxiella burnetii.

D. Bartonella henselae.

E. Mycobacterium haemophilum.

10. A 5-year-old child presented to her pediatrician with bloody diarrhea of 2 days’ duration accompanied by abdominal cramps and dehydration. She was afebrile. She had become symptomatic 4 days after consuming potato salad, a hamburger, and milk. Examination of growth of the stool specimen on sorbitol-MacConkey agar plates coupled with a positive enzyme immunoassay (EIA) stool test provided the diagnosis. Which one of the following is the most likely pathogen in this case?

B. Shiga toxin-producing Escherichia coli.

C. Salmonella enterica.

D. Yersinia enterocolitica.

E. Campylobacter jejuni.

11. A 70-year-old woman presented to the emergency department with a fever of 102°C, a cough, and night sweats. She frequently visits Lebanon, where her family resides. Slow-growing, small coccobacillary rods were isolated from blood cultures after 48 hours on chocolate and sheep blood agar; no growth was observed on MacConkey plates. The pathogen was oxidase and urease positive and was identified by a rise in serologic titers. Which one of the following is the most likely etiologic agent?

B. Mycobacterium tuberculosis.

C. Brucella melitensis.

D. Bordetella bronchiseptica.

E. Haemophilus influenza.

12. A 14-year-old male sustained a traumatic injury to his foot from a jagged seashell while at the beach. The next day he presented to the emergency department with a high fever and erythema, with diffuse swelling and purulent drainage from the foot and ankle. The Gram stain from drainage revealed the presence of curved gram-negative bacilli. Which one of the following is the most likely pathogen?

B. Haemophilus influenza.

C. Vibrio vulnificus.

D. Campylobacter jejuni.

E. Pasteurella multocida.

B. Streptococcus pneumonia.

C. Streptococcus agalactiae.

D. Staphylococcus aureus.

E. Staphylococcus epidermidis.

14. Which one of the following Gram stain components acts as a counterstain?

B. Iodine.

C. Crystal violet.

D. Acetone alcohol.

E. Methylene blue.

15. Which one of the following bacteriologic media is considered both differential and selective?

B. Chocolate agar.

C. MacConkey agar.

D. Brucella agar.

E. Mueller Hinton agar.

B. Proteus mirabilis.

C. Pseudomonas aeruginosa.

D. Proteus vulgaris.

E. Serratia liquefaciens.

17. An 80-year-old woman was admitted from a long-term care facility for worsening diarrhea. She had received antibiotics the previous week for a urinary tract infection. Endoscopy revealed the presence of pseudomembranous colitis. Which one of the following is the best treatment regimen to initiate?

B. Clindamycin.

C. Levofloxacin.

D. Fluconazole.

E. Vancomycin.

18. A 6-week-old infant presented to the pediatrician with a 7-day history of symptoms of a mild cold that progressed to paroxysms of coughing, gasping for breath, and vomiting. Upon admission to the hospital, a chest radiograph was taken and found to be normal. Nasopharyngeal swabs were diagnostic for the illness. Which one of the following is the most likely pathogen?

B. Group A streptococci (GAS).

C. Streptococcus pneumoniae.

D. Bordetella pertussis.

E. Moraxella catarrhalis.

19. A 12-year-old child presented the emergency department with facial edema, a 3-day history of dark-colored urine, and a sore throat of 10 days’ duration. Laboratory results showed hematuria and proteinuria. Urine and blood cultures were negative, and a throat culture grew β-hemolytic gram-positive cocci in chains. The presumptive diagnosis was acute glomerulonephritis. Which one of the following is the most likely etiologic agent of this disease?

B. Streptococcus agalactiae (GBS).

C. Enterococcus faecium.

D. Streptococcus pneumoniae.

E. Streptococcus mutans.

20. A patient presented to the emergency department with shortness of breath and fever. A chest radiograph revealed a left lower lobe infiltrate and right pleural effusion. His family indicated that he became symptomatic several days after visiting a petting zoo. Both blood cultures and pleural fluid grew oxidase-negative, small gram-negative coccobacilli on sheep blood agar, but there was no growth on MacConkey agar. Which one of the following is the most likely cause of the infection?

B. Capnocytophaga canimorsus.

C. Burkholderia pseudomallei.

D. Yersinia pestis.

E. Francisella tularensis.

21. A 7-month-old infant presented to the emergency department after 1 day of bloody diarrhea and fever. He was transferred to the pediatric intensive care unit in septic shock. Onset of symptoms occurred shortly after the family’s purchase of an iguana. Stool and blood cultures yielded gram-negative bacilli that appeared as red colonies with a black center on xylose-lysine-deoxycholate and colorless colonies on MacConkey media. Which one of the following is the most likely etiologic agent causing this infection?

B. Salmonella spp.

C. Campylobacter jejuni.

D. E. coli O157:H7.

E. Yersinia enterocolitica.

22. Gram-positive cocci in clusters were isolated from a breast abscess of a 30-year-old diabetic woman. The bacteria were slide-coagulase positive and tube coagulase negative. Both the pyrrolidonyl arylamidase (PYR) and ornithine decarboxylase tests were positive. Which one of the following is the most likely pathogen?

B. Staphylococcus lugdunensis.

C. Staphylococcus epidermidis.

D. Staphylococcus schleiferi.

E. Staphylococcus haemolyticus.

23. Small, gram-negative coccobacilli grew from a blood culture collected from a patient with ventilator-associated pneumonia. The isolate was oxidase negative and nonmotile, produced colorless colonies on MacConkey agar, and was multi-drug resistant. Which one of the following is the most likely pathogen identified by this workup?

B. Klebsiella pneumoniae.

C. Acinetobacter baumannii.

D. Stenotrophomonas maltophilia.

E. Pseudomonas aeruginosa.

24. Which one of the following methods is most commonly used in molecular epidemiology to generate strain-specific molecular fingerprints to determine microbial strain relatedness in a hospital setting?

B. Staphylococcal cassette chromosome mec (SCCmec).

C. Peptide nucleic acid fluorescent in situ hybridization.

D. Pulsed-field gel electrophoresis (PFGE).

E. Matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry.

25. A patient presented to the adolescent clinic with symptoms of dysuria and a purulent vaginal discharge. She gave a history of being sexually active with one partner over the past 2 months. A urine specimen tested positive for Neisseria gonorrhoeae. Which one of the following diagnostic tests is best for rapid detection of the etiologic agent?

B. Gene sequencing.

C. Cell culture.

D. NAAT.

E. Gram stain.

26. A 30-year-old woman with a prior history of recurrent episodes of cystitis presented to her private practitioner with urinary urgency and dysuria. A urinalysis and culture were ordered, and results were positive for leukocyte esterase, nitrite, and growth of more than 10⁴ colony forming units (CFU)/mL of lactose-fermenting, oxidase-negative, indole-positive, gram-negative bacilli. Which one of the following is the most likely pathogen?

B. Proteus mirabilis.

C. Acinetobacter baumannii.

D. Pseudomonas aeruginosa.

E. Escherichia coli.

27. A 23-year-old woman in her second trimester of pregnancy presented to her obstetrician with symptoms of malodorous vaginal discharge. Specimens were sent to the microbiology laboratory, where a Gram stain detected the cause of her bacterial infection. Which one of the following is the most likely cause of this infection?

B. Chlamydia trachomatis.

C. Trichomonas.

D. Neisseria gonorrhoeae.

E. Candida albicans.

28. The foul-smelling purulent drainage from the surgical wound of a patient with a ruptured appendix was sent for culture. The Gram stain showed gram-negative bacilli, and the culture grew Bacteroides fragilis, Citrobacter freundii, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Escherichia coli. Which one of the following anaerobic pathogens is the most likely cause of this infection?

B. Enterobacter aerogenes.

C. Veillonella parvula.

D. Pseudomonas aeruginosa.

E. Escherichia coli.

29. A 17-year-old patient with cystic fibrosis presented to her pulmonologist with increased respiratory secretions and difficulty breathing. A sputum specimen was sent for culture. Four days later a presumptive identification was obtained for a slow-growing, short, gram-negative nonlactose fermenter that was weakly oxidase positive. Which one of the following is the most likely etiologic agent?

B. Klebsiella pneumonia.

C. Burkholderia cepacia complex.

D. Acinetobacter lwoffii.

E. Stenotrophomonas maltophilia.

B. Streptococcus pneumoniae.

C. Clostridium species.

D. Corynebacterium species.

E. Enterococcus species.

31. Rapid phenotypic tests are often used in the microbiology laboratory as an aid in the identification algorithm. Which one of the following phenotypic tests can differentiate enterococci from staphylococci?

B. The PYR reaction.

C. The oxidase reaction.

D. The catalase reaction.

E. The hippurate reaction.

32. A positive blood culture obtained from a septic patient in the intensive care unit was reported as Escherichia coli resistant to piperacillin, ceftazidime, and aztreonam but susceptible to imipenem and cefoxitin. Which one of the following mechanisms of resistance does this pathogen exhibit?

B. Metallo-β-lactamase.

C. Carbapenemase.

D. AmpC β-lactamase.

E. ESBL.

33. A 58-year-old man presented to the emergency department with fever and shortness of breath. A chest radiograph was consistent with pneumonia. A rapid urine antigen test revealed the likely causative agent, and he was discharged with a 2-week course of levofloxacin. Routine bacteriology cultures failed to recover the pathogen. Which one of the following is the most likely cause of his pneumonia?

B. Staphylococcus aureus.

C. Haemophilus influenza.

D. Mycobacterium tuberculosis.

E. Influenza A.

B. Patient results can be reported because this rapid device has a very high specificity.

C. Patient results can be reported because this rapid device has a very high sensitivity.

D. The result should be reported as negative because the control line is not present.

E. The patient result is invalid because the control line is not present.

35. An 88-year-old woman presented to the emergency department with signs and symptoms of pneumonia. She had shortness of breath, tachycardia, and a fever of 102°F. Sputum was obtained and sent for bacterial culture. Gram stain demonstrated many polymorphonuclear leukocytes and small, faintly staining gram-negative coccobacilli. After 24 hours, only the chocolate agar plate demonstrated growth. Which one of the following tests is most useful for identifying this pathogen?

B. PYR reaction.

C. Bacitracin susceptibility.

D. X and V factor growth requirements.

E. Bile solubility.

36. An 18-year-old college student presented to her campus health clinic with complaints of sore throat, lymphadenopathy, and low-grade fever. A rapid “strep test” was negative. The student was not prescribed antibiotics based on a presumptive diagnosis of a virus infection. Due to persistent symptoms, a bacterial throat culture was obtained. Twenty-four hours later the pathogen was identified. Which one of the following is the most likely cause of her pharyngitis?

B. Haemophilus influenza.

C. Streptococcus dysgalactiae subspecies equisimilis.

D. Streptococcus pneumonia.

E. GBS.

B. Campylobacter jejuni.

C. Salmonella enteritidis.

D. Cryptosporidium parvum.

E. Clostridium difficile.

B. Pseudomonas aeruginosa.

C. Acinetobacter baumannii.

D. Stenotrophomonas maltophilia.

E. Serratia marcescens.

39. Commercially available multiplex PCR assays are used to detect bloodstream infections caused by Staphylococcus aureus and methicillin-resistant S. aureus (MRSA). These methods are designed to detect pathogen-specific molecular targets directly from newly positive blood culture bottles showing gram-positive cocci in clusters. Which one of the following answers best describes the genetic regions targeted in these assays?

B. Staphylococcal Panton-Valentine leukocidin (PVL), spa gene, and mecA gene.

C. Staphylococcal protein A (spa), SCCmec–orfX junction, and vanA gene.

D. nuc gene, mupA gene, and mecA gene.

E. SCCmec–orfX junction, agr gene, and mecA gene.

B. Klebsiella pneumoniae.

C. Stenotrophomonas maltophilia.

D. Pseudomonas aeruginosa.

E. Escherichia coli.

41. The microbiology laboratory evaluated a new agar media (agar B) developed to be both selective and differential for MRSA with claims of enhanced sensitivity. A total of 500 nares swabs were inoculated onto the laboratory’s current MRSA agar (agar A, the gold standard) and onto agar B. Concordance was observed for 138 positive and 337 negative cultures. Fourteen specimens were positive on agar A and negative on agar B. Eleven specimens were positive on agar B and negative on agar A. Based on this data, which one of the following statements is correct?

B. Agar B demonstrated a lower sensitivity of 90.8%.

C. Agar B demonstrated a higher sensitivity of 96.0%.

D. Agar B demonstrated a lower sensitivity of 95%.

E. Agar B demonstrated a lower sensitivity of 92.6%.

42. Which one of the following set of parameters for performing antimicrobial susceptibility testing of aerobic, nonfastidious bacteria best follows established practice guidelines?

B. 1.0 McFarland inoculum, Mueller Hinton agar with 5% sheep blood agar, CO₂ incubation.

C. 1.0 McFarland inoculum, Mueller Hinton agar with 5% sheep blood agar, ambient air incubation.

D. 1.0 McFarland inoculum, Mueller Hinton agar, ambient air incubation.

E. 0.5 McFarland inoculum, Mueller Hinton agar, CO₂ incubation.

B. Nocardia cyriacigeorgica.

C. Rhodococcus equi.

D. Gordonia sputa.

E. Mycobacterium fortuitum.

B. Porphyromonas asaccharolytica.

C. Fusobacterium nucleatum.

D. Bacteroides fragilis.

E. Clostridium septicum.

45. An elderly man was transferred from a nursing home to your hospital with low-grade fever, flank pain, hypothermia, dysuria, and nausea. His workup included blood cultures and a urine specimen. The urine specimen grew 10⁴ non–β-hemolytic colonies of gram-positive cocci in pairs and chains on blood agar media. Which one of the following is the most likely agent causing this infection?

B. Enterococcus faecium.

C. Staphylococcus saprophyticus.

D. GAS.

E. Staphylococcus aureus.

46. A 10-year-old girl presented to the emergency department with signs and symptoms of depression. Her mother reported disruptive behavior at school and suspects sexual abuse. Urine and vaginal discharge specimens were sent to the microbiology laboratory for analysis. Which one of the following statements best describes the tests that must be performed to optimize detection of sexually transmitted pathogens?

B. Direct fluorescent antibody tests and serology.

C. NAATs and serology.

D. Viral culture and serology.

E. Gram stain and NAATs.

47. A 48-year-old man presented to an outpatient clinic with a 1-week history of daily fevers to 102°F. On physical exam a new heart murmur was detected. He was referred to the emergency department for a transesophageal echocardiogram, which identified a vegetation on the aortic valve. Blood cultures were collected, and 24 hours later gram-positive cocci in pairs and tetrads were reported. The organism was α-hemolytic, PYR positive, leucine aminopeptidase (LAP) negative, and susceptible to vancomycin. Which one of the following is the most likely etiologic agent?

B. Aerococcus urinae.

C. Streptococcus pneumoniae.

D. Pediococcus acidilactici.

E. Aerococcus viridians.

B. Closely related.

C. Possibly related.

D. Different.

E. Inconclusive.

49. An 18-year-old patient was admitted to the hospital with fever, hypotension, altered mental status, and an erythematous abscess on her leg that was developing a blackened eschar. A diagnosis of necrotizing fasciitis was made. Blood cultures were collected, and the abscess was cultured. The Gram stain revealed gram-positive cocci in clusters. Which one of the following is the most likely etiologic agent?

B. Bacillus anthracis.

C. Beta-hemolytic Streptococcus pyogenes (GAS).

D. MRSA.

E. Staphylococcus lugdunensis.

B. Fluorochrome stain and NAAT.

C. Giemsa stain and liquid culture.

D. Fluorochrome stain and nucleic acid sequencing.

E. DNA probe assay and high-pressure liquid chromatography.

51. A tissue biopsy obtained from a 5-year-old child with submandibular lymphadenitis was positive on direct examination for acid-fast bacilli. Nonchromogenic slow-growing colonies were observed only on chocolate agar at 30°C and not on standard mycobacterial media at 37°C. Which one of the following is the most likely etiologic agent?

B. Mycobacterium haemophilum.

C. Mycobacterium avium.

D. Mycobacterium leprae.

E. Mycobacterium marinum.

52. A thin, immunocompetent, 85-year-old woman presents with chronic obstructive pulmonary disease and a chronic cough. Sputum smears were acid-fast positive, and a nonchromogenic mycobacterial isolate grew from multiple specimens after 21 days of culture. Which one of the following is the most likely etiologic agent causing her infection?

B. Mycobacterium kansasii.

C. Mycobacterium avium complex.

D. Mycobacterium scrofulaceum.

E. Mycobacterium gordonae.

53. A 43-year-old HIV-positive man presented to the emergency department with a 2-month history of fever, night sweats, cough with productive sputum, and a 20-pound weight loss. He was recently released from prison. Three sputum specimens were positive for acid-fast bacilli (AFB). Which one of the following statements best describes the conventional methods used for diagnosis and identification of this pathogen?

B. Culture on standard media used to isolate bacterial agents causing community-acquired pneumonia.

C. Cavitary lesions on chest radiographs, which are diagnostic of tuberculosis.

D. Culture on mycobacterial selective media, along with the use of DNA probes and biochemical tests.

E. The use of NAATs identifying the Mycobacterium avium complex.

54. A 52-year-old man living in southern Louisiana presents with multiple, hyposensitive, irregularly shaped, annular macules on his arms and back and bilateral numbness of his hands. Kinyoun carbol fuchsin staining of a skin biopsy shows AFB, but culture of the biopsy tissue is negative. He reports no travel history outside the United States and frequently hunts deer and armadillos. Which one of the following is the most likely etiologic cause of his disease?

B. Borrelia burgdorferi.

C. Treponema pallidum.

D. Nocardia brasiliensis.

E. Mycobacterium leprae.

55. Which of the following statements best describes species of mycobacteria that are classified as nontuberculous mycobacteria?

B. Mycobacterium kansasii, Mycobacterium abscessus, and Mycobacterium avium-intracellulare complex.

C. Mycobacterium avium-intracellulare complex, Mycobacterium microti, and Mycobacterium mucogenicum.

D. Mycobacterium chelonae, Mycobacterium africanum, and Mycobacterium scrofulaceum.

E. Mycobacterium gordonae, Mycobacterium bovis, and Mycobacterium kansasii.

56. An asymptomatic health care worker from India had a positive tuberculin skin test. She had a history of Bacille Calmette-Guerin vaccination. Which one of the following tests should be performed to confirm the diagnosis of latent tuberculosis?

B. Purified protein derivative inoculation.

C. Chest radiograph.

D. Adenosine deaminase assay.

E. Galactomannan assay.

57. A 29-year-old woman presented to her physician with a papular rash on her calf that developed 2 weeks after receiving a tattoo. A punch biopsy showed inflammatory cells but no microorganisms. Upon culture nonchromogenic, AFB grew within 7 days. The results of biochemical tests included negative iron uptake, positive citrate utilization, and NaCl intolerance. Which one of the following is the most likely etiologic agent?

B. Mycobacterium chelonae.

C. Mycobacterium abscessus.

D. Mycobacterium fortuitum.

E. Mycobacterium szulgai.

58. Which one of the following phenotypic methods can best be used to differentiate Mycobacterium tuberculosis from Mycobacterium bovis?

B. Urease.

C. Growth on MacConkey agar.

D. Niacin.

E. Pigment production.

59. Subtyping of strains of Mycobacterium tuberculosis is important for epidemiologic purposes. Which one of the following methods is considered the current gold standard for molecular typing of M. tuberculosis isolates?

B. IS6110 restriction length polymorphism analysis.

C. Spacer oligonucleotide typing (spoligotyping).

D. Mycobacterial interspersed repetitive units/variable number tandem repeat (MIRU-VNTR) typing.

E. Genome-wide single nucleotide polymorphism analysis.

60. A patient who immigrated to the United States from China presented to her clinician with a chronic productive cough and a 1-month history of treatment with isoniazid. A chest radiograph revealed a nodular infiltrate in the apex of the upper lobe. The patient had a positive tuberculin skin test. Which one of the following is the most effective initial treatment regimen?

B. Fluoroquinolone, pending drug susceptibility results.

C. Second-line drugs (e.g., ethionamide, cycloserine, kanamycin), pending drug susceptibility results.

D. Treatment with isoniazid, rifampin, pyrazinamide, and ethambutol, pending drug susceptibility results.

E. Isoniazid plus ethambutol is adequate to avoid the hepatotoxicity of rifampin.

B. The isolate is a multi-drug-resistant tuberculosis strain.

C. The isolate is rifampin monoresistant.

D. The isolate is low-level isoniazid resistant and rifampin susceptible.

E. The results cannot be interpreted due to culture contamination of the control quadrant.

62. A 2-year-old child presented to the emergency department with painless unilateral enlargement of a cervical lymph node. A fine-needle aspirate was performed, and the specimen was sent to the microbiology laboratory for culture. Which one of the following is the most likely pathogen?

B. Mycobacterium gordonae.

C. Mycobacterium mucogenicum.

D. Mycobacterium kansasii.

E. Mycobacterium abscessus.

63. Which one of the following species of nontuberculous mycobacteria is not a photochromogen?

B. Mycobacterium kansasii.

C. Mycobacterium marinum.

D. Mycobacterium simiae.

E. Mycobacterium asiaticum.

64. Operational safety requirements are mandated to prevent transmission of Mycobacterium tuberculosis to personnel who process potentially infectious specimens and cultures. Which one of the following most accurately describes the correct safety practice(s) requirements to ensure personnel safety?

B. Air sterilization by ultraviolet light within a BSC and on the ceiling of the room to disinfect the ambient air.

C. A room or suite that has a minimum of 20 air exchanges per hour to remove 99% of airborne particulates.

D. A BSC in a controlled access area with the capacity to draw 75 to 100 linear feet of air per minute across the entire front opening for proper functioning of the HEPA filter.

E. Respiratory protection using a HEPA-filtered respirator, such as the N95 or N100, and mandatory fit testing every 6 months.

65. AFB were detected in sputum specimens from a cluster of patients in your hospital. Cultures from respiratory specimens and water sources produced slow-growing, yellow pigmented AFB that grew optimally at 42°C, were arylsulfatase test positive, and were negative by commercial rRNA probe assays. Which one of the following is the most likely etiologic agent?

B. Mycobacterium xenopi.

C. Mycobacterium abscessus.

D. Mycobacterium kansasii.

E. Mycobacterium mucogenicum.

66. From the nontuberculous mycobacteria species listed below, which one is most often considered to be clinically relevant when isolated from the sputum of a patient with symptoms indicative of nontuberculous mycobacterial lung disease?

B. Mycobacterium lentiflavum.

C. Mycobacterium terrae.

D. Mycobacterium intracellulare.

E. Mycobacterium gordonae.

67. AFB were detected in a bronchoalveolar lavage specimen from a patient presenting with a chronic cough and a chest radiograph suspicious for tuberculosis. The nucleic acid hybridization probe test result was negative for M. tuberculosis complex and positive for another mycobacterial species. The isolate was yellow after exposure to light. Which one of the following is the most likely etiologic agent?

B. Mycobacterium scrofulaceum.

C. Mycobacterium gordonae.

D. Mycobacterium kansasii.

E. Mycobacterium abscessus.

68. Proper isolation practices in patients with suspected or confirmed pulmonary tuberculosis are the primary protective measures against the spread of tuberculosis to other patients and staff. Which one of the following statements most accurately reflects the infection control criteria for release from airborne isolation?

B. Airborne isolation can be discontinued when two sputum specimens are AFB smear negative and culture negative.

C. Airborne isolation can be discontinued when the patient has received 48 hours of antituberculous therapy.

D. Airborne precautions can be discontinued in young children when three expectorated sputum specimens are AFB smear negative and culture negative.

E. Airborne isolation can be discontinued when two sputum specimens are AFB smear negative and nucleic acid probe test negative.

69. An 8-year-old child who recently traveled to rural Mexico presented to the pediatric emergency department with severe abdominal pain. She was taken to the operating room, where a nodular omental mass was noted near the colon. Peritoneal fluid and tissue specimens were sent to microbiology for analysis. A positive NAAT and molecular analysis identified the mycobacterial pathogen. Which one of the following species is the most likely etiologic agent?

B. Mycobacterium ulcerans.

C. Mycobacterium bovis.

D. Mycobacterium avium complex.

E. Mycobacterium fortuitum.

70. A 32-year-old HIV-positive patient presents to the emergency department with a chronic cough of 4 months’ duration. The chest radiograph shows bilateral infiltrates. Respiratory specimens are submitted for analysis. Which one of the following statements best describes the rapid mycobacteriology tests that are used to detect these pathogens directly in clinical specimens?

B. Fluorochrome stain and NAAT.

C. Giemsa stain and liquid culture.

D. Fluorochrome stain and nucleic acid sequencing.

E. DNA probe assay and high-pressure liquid chromatography.

B. Aspergillus nidulans.

C. Trichophyton rubrum.

D. Fusarium solani.

E. Cryptococcus neoformans.

B. Aspergillosis.

C. Candidiasis.

D. Mycetoma.

E. Rhinosporidiosis.

B. Penicillium spp.

C. Aspergillus niger.

D. Fusarium solani.

E. Aspergillus flavus.