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Antimicrobial and Antiviral Pharmacology

Antibacterials

Antimycobacterials

Antifungals

Antivirals/Antiretrovirals

Antiprotozoals

Questions

413. You are a physician and epidemiologist employed by the US Centers for Disease Control and Prevention. You get an urgent phone call stating that an envelope was opened in the mail room of a large corporation, and similar ones were delivered to various government offices. Some sort of white powder fell out and was blown around the room, exposing dozens of workers. The suspicion is anthrax. Which drug would be best, most properly indicated, for prophylaxis if the substance tests positive for Bacillus anthracis?

a. Azithromycin

b. Clarithromycin

c. Doxycycline

d. Hydroxychloroquine

e. Metronidazole

414. A jaundiced 1-day-old premature infant with an elevated free bili-rubin is seen in the premature baby nursery. The mother had received an antibiotic combination for a urinary tract infection (UTI) 1 week before delivery. Which antibiotic drug or class was the most likely cause of the baby’s kernicterus?

a. An aminopenicillin (eg, amoxicillin)

b. Azithromycin

c. Erythromycin

d. Fourth-generation cephalosporin

e. Sulfamethoxazole plus trimethoprim

415. You are caring for a patient with HIV infection and will start drug therapy initially with the nucleoside analog zidovudine (formerly called azidothymidine, or AZT). Which statement most correctly describes zidovudine or the dideoxynucleoside class to which it belongs?

a. Levels of active metabolite in cerebrospinal fluid usually are not detectable (ie, zero) because it cannot cross the blood–brain barrier

b. Resistance to these antivirals develops rapidly after monotherapy starts, involves decreased incorporation of active metabolite into viral DNA

c. The dideoxynucleoside stops viral nucleic acid synthesis

d. The active metabolite is an equally effective substrate for viral reverse transcriptase and mammalian DNA polymerase, which explains the high incidence of host toxicity

e. Zidovudine is dephosphorylated to form the active metabolite, which is incorporated into viral nucleic acid via HIV reverse transcriptase

416. A patient on antimicrobial therapy develops the following signs and symptoms that ultimately are found to be drug-induced: cough, dyspnea, and pulmonary infiltrates; neutropenia and bleeding tendencies; and paresthesias. What was the most likely cause of this patient’s symptoms?

a. Amoxicillin

b. Azithromycin

c. Ciprofloxacin

d. Isoniazid

e. Nitrofurantoin

417. A patient presents with severe, unrelenting diarrhea, and the fluid and electrolyte imbalances one would expect from that. She had been started on an antibiotic recently, and the likely diagnosis is antibiotic-associated pseudomembranous colitis (AAPMC). What drug was the most likely cause?

a. Amoxicillin

b. Azithromycin

c. Clindamycin

d. Metronidazole

e. Trimethoprim plus sulfamethoxazole (TMP-SMZ)

418. A 35-year-old woman complains of itching in the vulval area. Hanging-drop examination of the urine reveals trichomonads. What is the preferred treatment for the trichomoniasis?

a. Doxycycline

b. Emetine

c. Metronidazole

d. Pentamidine

e. Pyrazinamide

419. A patient will be started on primaquine to treat active Plasmodium vivax malaria, specifically to target the hepatic forms of the parasite. Before you administer the drug you should screen the patient to assess their relative risk of developing a relatively common and severe adverse response to the drug. What is that primaquine-associated risk?

a. Cardiac conduction disturbances

b. Hemolytic disease

c. Nephrotoxicity

d. Retinopathy

e. Seizures, convulsions

420. On morning rounds in the hospital you encounter a patient being treated with linezolid, the first approved member of the oxazolidine class of antimicrobials. Which statement accurately describes a characteristic of this drug?

a. Exerts strong bactericidal effects

b. Mainly used for relatively minor infections with gram-negative organisms

c. Preferred alternative to amoxicillin for children with otitis media

d. Preferred alternative to ciprofloxacin for B. anthracis infections

e. Suitable for vancomycin-resistant enterococci

421. A 59-year-old woman is diagnosed with tuberculosis (TB). Before prescribing a multidrug regimen, you take a careful medication history because one of the drugs commonly used to treat TB induces some of the microsomal cytochrome P450 enzymes in the liver, and is a common cause of drug–drug interactions. What is the most likely drug?

a. Ethambutol

b. Isoniazid

c. Pyrazinamide

d. Rifampin

e. Vitamin B₆

422. A patient with HIV infection is receiving a combination of protease inhibitors as part of overall antiviral therapy. What is, ordinarily, the most likely/most common side effect(s) of the protease inhibitors?

a. Anemia and neutropenia

b. Hyperglycemia and hyperlipidemia

c. Lactic acidosis

d. Neuropathy

e. Pancreatitis

423. A 27-year-old woman has just returned from a trip to Southeast Asia. Over the past 24 hours she has developed shaking, chills, and a temperature of 104°F. A blood smear reveals Plasmodium vivax. What drug would you prescribe to eradicate the extraerythrocytic phase of the organism?

a. Chloroguanide

b. Chloroquine

c. Primaquine

d. Pyrimethamine

e. Quinacrine

424. A patient has a severe bacterial infection that normally would respond to an oral penicillin or cephalosporin. However, his chart documents anaphylactoid reactions to both classes of drugs. Given the history, what drug would be preferred for treating the infection, and also poses the least risk of cross-reactivity and an allergic response?

a. Clotrimazole

b. Gentamicin

c. Metronidazole

d. Tetracycline

e. Vancomycin

425. A 40-year-old man is HIV-positive and has a cluster-of-differentiation-4 (CD4) count of 200/mm³. Within 2 months after starting drug therapy for his HIV he develops a peripheral white blood cell count of 1000/mm³ and a hemoglobin of 9.0 mg/dL. Which drug most likely caused the hematologic abnormalities?

a. Acyclovir

b. Dideoxycytidine

c. Foscarnet

d. Rimantadine

e. Zidovudine

426. An 86-year-old man complains of cough and blood in his sputum for the past 5 days. On admission, his temperature is 103°F. Physical examination reveals rales in his right lung, and x-ray examination shows increased density in the right middle lobe. A sputum smear shows many grampositive cocci, confirmed by sputum culture as penicillinase-producing Staphylococcus aureus. Which antibiotic would be best to administer first?

a. Ampicillin

b. Mezlocillin

c. Oxacillin

d. Penicillin (G or V)

e. Ticarcillin

427. When considering all the main antibacterial drugs that work by inhibiting protein synthesis in one way or another, virtually every one exerts bacteriostatic actions. Which drug or drug class differs from the rest because the usual consequence of therapeutic plasma levels is bactericidal, rather than mere inhibition of bacterial growth and replication?

a. Aminoglycosides

b. Clindamycin

c. Erythromycins

d. Linezolid

e. Tetracyclines

428. A patient with HIV infection and clinical AIDS is treated with a combination of agents, one of which is zidovudine. Which enzyme or replicative process is the main target of this antiviral drug?

a. Nonnucleoside reverse transcriptase

b. Nucleoside reverse transcriptase

c. RNA synthesis

d. Viral particle assembly

e. Viral proteases

429. A patient with HIV/AIDS, being treated with multiple antiviral and immunosuppressive drugs, develops an opportunistic infection caused by P. jiroveci. Which drug are you most likely to use to treat the pulmonary infection caused by this protozoan?

a. Carbenicillin

b. Metronidazole

c. Nifurtimox

d. Penicillin G

e. Pentamidine

430. A 25-year-old woman with an upper respiratory tract infection caused by H. influenzae is treated with trimethoprim-sulfamethoxazole. She responds well in a matter of days after starting the TMP-SMZ. Which bacterial process is inhibited by this combination, and accounts for the antibacterial effects?

a. Cell-wall synthesis

b. Protein synthesis

c. Folic acid synthesis

d. Topoisomerase II (DNA gyrase)

e. DNA polymerase

431. A man who has been at the local tavern, drinking alcohol heavily, is assaulted. He is transported to the hospital. Among various findings is an infection for which prompt antibiotic therapy is indicated. Given his high blood alcohol level, which antibiotic should be avoided because of a high potential of causing a serious disulfiram-like reaction that might provoke ventilatory or cardiovascular failure? (Assume that were it not for the alcohol consumption, the antibiotic would be suitable for the infectious organisms that have been detected.)

a. Amoxicillin

b. Cefotetan

c. Erythromycin ethylsuccinate

d. Linezolid

e. Penicillin G

432. A 43-year-old woman is recovering from major surgery, following discharge from the hospital, in an assisted-care facility. She develops fever, rales, dyspnea, cough, and purulent sputum. Results of a chest radiograph indicate bilateral pulmonary infiltrates. We send blood and sputum cultures to the clinical pathology lab for culturing, but now must turn our attention to what we believe is community-acquired pneumonia caused by antibiotic-resistant pneumococci. We want to start empiric antibiotic therapy until culture results are available. Which drug would be best for this initial therapy?

a. Amoxicillin

b. Cefazolin

c. Erythromycin

d. Levofloxacin

e. Penicillin G

f. Vancomycin

433. Blood and sputum cultures taken in a critically ill 26-year-old woman indicate the presence of MRSA—methicillin-resistant Staph. aureus. Which drug is most likely to be effective in treating this infection?

a. Amoxicillin plus clavulanic acid

b. Clindamycin

c. Erythromycin

d. Trimethoprim-sulfamethoxazole (TMP-SMZ)

e. Vancomycin

434. Compared with most other cephalosporins, the administration of cefmetazole, cefoperazone, or cefotetan is associated with a higher incidence of an adverse response that is particularly dangerous for some patients. What is that rather unique adverse response?

a. Acute heart failure

b. Acute renal failure

c. Bleeding tendencies in patients taking warfarin

d. Hypertension

e. Ototoxicity

435. A patient develops muscle aches and pains during the course of antibiotic therapy. A muscle biopsy would clearly show myopathy. Which drug most likely (and rather uniquely) caused this adverse effect on skeletal muscle?

a. Daptomycin

b. Erythromycin

c. Gentamicin

d. Linezolid

e. Vancomycin

436. A patient with an infectious disease routinely takes their antimicrobial medication with milk or other dairy products in an attempt to reduce stomach upset from the drug. The antibiotic fails to work adequately because calcium in the dairy products chelates the drug and reduces its oral bioavailability. Which antimicrobial drug or drug class was the patient most likely taking?

a. Aminoglycoside

b. Antimycobacterial drug, specifically isoniazid

c. Cephalosporin, first generation

d. Cephalosporin, third generation

e. Penicillin

f. Tetracycline

437. A patient develops profuse, watery diarrhea, fever, abdominal pain, and leukocytosis in response to antibiotic therapy. C. difficile infection in the gut is confirmed. What is the preferred agent for therapy of this antibiotic-associated pseudomembranous colitis (AAPMC)?

a. Amphotericin B

b. Clindamycin

c. Gentamicin

d. Metronidazole

e. Trimethoprim plus sulfamethoxazole (TMP-SMZ)

438. A patient has been taking warfarin for several months and his INR (normalized prothrombin time) has been kept within the desired therapeutic range consistently. They develop an infection and are started on antibiotic therapy. Shortly thereafter their INR rises to eight (very high) and they develop epistaxis and other indicators of excessive bleeding. Which antibiotic most likely interacted with the warfarin, increasing its blood levels and effects, by inhibiting warfarin’s metabolism by the hepatic P-450 system?

a. Azithromycin

b. Erythromycin

c. Gentamicin

d. Penicillin G

e. Rifampin

439. Ampicillin and amoxicillin are in the same group of penicillins (broad spectrum, or aminopenicillins). However, there is one clinically important difference. Which phrase best states how amoxicillin differs from ampicillin?

a. Has better oral bioavailability, particularly when taken with meals

b. Is effective against penicillinase-producing organisms

c. Is a broad-spectrum penicillin

d. Does not cause hypersensitivity reactions

e. Has great antipseudomonal activity

440. A patient’s history notes a documented severe (anaphylactoid) reaction to a penicillin. What other antibiotic or class is likely to cross-react and so should be avoided in this patient?

a. Aminoglycosides

b. Azithromycin

c. Cephalosporins

d. Erythromycin

e. Linezolid

f. Tetracyclines

441. A 30-year-old woman develops a severe P. aeruginosa infection. The physician chooses to treat it with amikacin, not with gentamicin. Which phrase best describes how amikacin differs from gentamicin?

a. Does not require monitoring of blood levels during therapy

b. Exerts significant bactericidal effects against anaerobes too

c. Has broader spectrum against gram-negative bacilli

d. Lacks ototoxic potential

e. Protects against typical aminoglycoside nephrotoxicity

442. A 19-year-old being treated for leukemia develops a fever. You give several agents that will cover bacterial, viral, and fungal infections. Two days later, he develops acute renal failure. Which drug was most likely responsible?

a. Acyclovir

b. Amphotericin B

c. Ceftazidime

d. Penicillin G

e. Vancomycin

443. Penicillins, cephalosporins, and amphotericin B are quite different structurally, and the antimicrobial spectrum of amphotericin B is decidedly different from those of the other agents. Nonetheless, they all share a common property or action. Which statement identifies what that is?

a. Act, though various mechanisms, on cell walls or membranes of susceptible organisms

b. Contraindicated in immunocompromised patients

c. Interact with many drugs by inducing their hepatic metabolism

d. Leukopenia (decreased white cell counts) is a common side effect

e. Nephrotoxicity is common

444. Given the periodic worldwide outbreaks of “swine flu” (particularly influenza A virus subtype H1N1) there has been a great need for prophylactic measures in certain at-risk populations who may be susceptible. Which drug is generally recommended by the US Centers for Disease Control and Prevention for this purpose?

a. Acyclovir

b. Amantadine

c. Lopinavir

d. Oseltamivir

e. Ritonavir

445. A patient with a P. aeruginosa infection is receiving intravenous gentamicin. The aminoglycoside blood levels are well above the minimum inhibitory concentration (MIC), but the clinical response is not satisfactory. A new medication order calls for adding a penicillin, administered in a separate IV line to avoid a physical incompatibility. If this order is carried out, what is most likely to occur?

a. The aminoglycoside will inactivate the penicillin

b. The aminoglycoside will chemically neutralize and abolish the effects of the penicillin

c. The patient is likely to develop Clostridium difficile colitis (superinfection)

d. The penicillin will act synergistically with the aminoglycoside

e. The penicillin will increase the risk of aminoglycoside nephrotoxicity

f. The risk of inducing resistance to both drugs increases dramatically

446. Narrow spectrum penicillins, both penicillinase-sensitive and -resistant, have relatively poor activity against gram-negative bacteria. What is the main property or characteristic that explains why these micro-organisms do not respond well to the penicillins?

a. Actively transport any absorbed penicillin back to the extracellular space

b. Have an outer membrane that serves as a physical barrier to the penicillins

c. Lack a surface enzyme necessary to metabolically activate the penicillins

d. Lack penicillin-binding proteins

e. Metabolically inactivate these penicillins by mechanisms not involving β-lactamase

447. We have a patient with an intraabdominal infection, and Bacteroides fragilis is the main organism found upon culture. Which cephalosporin has the greatest activity against anaerobes such B. fragilis?

a. Cefaclor

b. Cefoxitin

c. Cefuroxime

d. Cephalexin

e. Cephalothin

448. A patient with a serious infection received intensive antibiotic therapy that leads to hearing loss. Which antibiotic most likely caused the ototoxicity?

a. Aminoglycoside (eg, gentamicin)

b. Cephalosporin, first-generation

c. Cephalosporin, third-generation

d. Fluoroquinolone (eg, ciprofloxacin)

e. Penicillin

449. A 26-year-old woman with acquired immunodeficiency syndrome (AIDS) develops cryptococcal meningitis. She refuses intravenous medication. Which antifungal agent is the best choice for oral therapy of the meningitis?

a. Amphotericin B

b. Fluconazole

c. Ketoconazole

d. Metronidazole

e. Nystatin

450. An adult patient is being treated with a parenteral aminoglycoside for a serious Pseudomonas aeruginosa infection. He requires immediate surgery. He is premedicated with midazolam, followed by administration of pro-pofol for induction. A dose of succinylcholine is often given for intubation (due to its rapid onset), with skeletal muscle paralysis maintained during surgery with vecuronium or another neuromuscular blocker in the same class (nondepolarizing, or competitive nicotinic receptor blocker). Other components of balanced anesthesia include nitrous oxide, isoflurane, and oxygen. What is the most likely outcome of having the aminoglycoside “on board” in the perioperative setting along with all these other drugs?

a. Acute hepatotoxicity from an aminoglycoside-isoflurane interaction

b. Antagonism of midazolam’s amnestic and sedative effects

c. Enhanced aminoglycoside toxicity to host cells

d. Increased or prolonged response to neuromuscular blockers

e. Reduced risk of catecholamine-induced cardiac arrhythmias

451. A patient with tuberculosis is started on isoniazid (INH) as part of a multidrug regimen. The physician also starts therapy with vitamin B₆ at the same time. What is the main reason for giving the vitamin B₆ prophylactically?

a. Facilitates INH renal excretion, thereby protecting against nephrotoxicity

b. Inhibits metabolism of INH, thereby increasing INH blood levels

c. Is a cofactor required for activation of the INH to its antimycobacterial metabolite

d. Potentiates the antitubercular activity of the INH

e. Prevents some adverse effects of INH therapy

452. One antibiotic is considered very effective in treatment of Rickettsia, Mycoplasma, and Chlamydia infections? It is also used to mange some patients with acne vulgaris lesions. To which drug does this description apply?

a. Bacitracin

b. Gentamicin

c. Penicillin G

d. Tetracycline

e. Vancomycin

453. You are starting therapy for an established HIV infection in a 28-year-old man. The drugs are ritonavir, lopinavir, zidovudine, and didanosine. This involves, of course, using two protease inhibitors and two nucleoside reverse transcriptase inhibitors (NRTIs). What is the main purpose of using the ritonavir?

a. Helps maintain adequate saquinavir levels by inhibiting its metabolism

b. Induces the metabolic activation of the NRTIs, which are prodrugs

c. Prevents the likely development of hypoglycemia

d. Reduces, or hopefully eliminates, lopinavir-mediated host toxicity

e. Serves as the main, most active, inhibitor of viral protease in this combination

454. As part of a multidrug attack on a patient’s infection with Myco bacterium tuberculosis, a physician plans to use an aminoglycoside antibiotic. Which drug is most active against the tubercle bacillus and seems to be associated with the fewest problems with resistance or typical aminoglycoside-induced adverse effects?

a. Amikacin

b. Kanamycin

c. Neomycin

d. Streptomycin

e. Tobramycin

455. Such agents as clavulanic acid, sulbactam, or tazobactam are often added to some proprietary (manufactured) penicillin combination products. What is the main reason for including them, or describes their action best?

a. Add antibiotic activity against Pseudomonas and many Enterobacter species

b. Facilitate antibiotic penetration into the central nervous system and cerebro-spinal fluid

c. Inhibit cell wall transpeptidases

d. Inhibit inactivation of penicillin by β-lactamase-producing bacteria

e. Inhibit the normally significant hepatic metabolism of the penicillin

f. Reduce the risk and/or severity of allergic reactions in susceptible patients

456. A patient with active tuberculosis is being treated with isoniazid (INH) and ethambutol as part of the overall regimen. What is the main effect expected of the ethambutol?

a. Facilitated entry of the INH into the mycobacteria

b. Facilitated penetration of the blood-brain barrier

c. Retarded absorption after intramuscular injection

d. Retarded development of organism resistance

e. Slowed renal excretion of INH to help maintain effective blood levels

457. A patient has a severe infection caused by anaerobic bacteria. The first-year house officer writes an order for gentamicin. This approach is doomed to fail because aminoglycosides have no activity against anaerobes. Which best explains why anaerobes will be resistant?

a. Cannot metabolize the aminoglycosides, which are all prodrugs, to their bactericidal free radical forms

b. Cannot oxidatively metabolize aminoglycosides to moieties that are nontoxic to host cells

c. Lack molecular oxygen that is a prerequisite for drug binding to the 50S subunit of bacterial ribosomes

d. Lack the ability to transport aminoglycosides from the extracellular milieu in the absence of oxygen

e. Synthesize more, and more active, resistance factors than do aerobic bacteria

458. In patients with hepatic coma or portal-systemic encephalopathy decreasing the production and absorption of ammonia from the gastrointestinal (GI) tract will be beneficial. What antibiotic would be most useful in this situation?

a. Cephalothin

b. Chloramphenicol

c. Neomycin

d. Penicillin G

e. Tetracycline

459. A 19-year-old girl who previously was healthy develops bacterial meningitis. What would you consider to be the drug of choice for this situation?

a. Ceftriaxone

b. Erythromycin

c. Penicillin G

d. Penicillin V

e. Procaine penicillin

460. A patient is being treated with an antibiotic for a vancomycin-resistant enterococcal (VRE) infection. They consume an over-the-counter medication containing ephedrine and develop a significant spike of blood pressure that leads to a pounding headache. They are transported to the hospital. As part of the work-up, blood tests indicate some bone marrow suppression. Which antibiotic is most likely associated with this clinical picture?

a. Azithromycin

b. Ciprofloxacin

c. Erythromycin estolate

d. Gentamicin

e. Linezolid

461. You just started a rotation on the Infectious Disease consult service. It is at an academic medical center that is in a major hub city for international travel, so unusual or uncommon diseases are commonly seen here. One of the patients is receiving ethambutol. What is the most likely reason for which this drug is being given?

a. Amphotericin-resistant Candida infection

b. E. coli infection, severe, with profound fluid and electrolyte loss

c. Entamoeba dispar infection (amebiasis)

d. M. tuberculosis infection

e. Plasmodium (malarial) infection

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