1. Bacteria are able to transfer genes that confer resistance to each other. This usually occurs via which of the following?
B. DNA gyrase
E. Nuclear fusion
2. A 13-year-old male patient has a sore throat but no cough. His pharynx, soft palate, and tonsils are red and edematous, with tonsillar exudate. His cervical lymph nodes are tender. There is no evidence of airway compromise. Before beginning drug treatment, which of the following should be assessed?
A. Sensitivity of the infecting organism to antibiotics
B. The ability to obtain intravenous access
C. Whether the patient is allergic to penicillin
D. Previous use of the antibiotic clindamycin
E. White blood cell count
3. A patient diagnosed as having pneumococcal (Streptococcus pneumoniae) pneumonia has received an intramuscular injection of an antibiotic in the clinic. The patient has received penicillins before without having an allergic reaction. For continued oral therapy on an outpatient basis, which of the following would be the most appropriate therapy?
D. Penicillin V
4. Broad-spectrum ampicillin is different from penicillin G in that it
A. has a lower Michaelis constant (Km) for the transpeptidases of many gram-negative bacteria.
B. covalently inactivates the transpeptidases of many gram-negative bacteria.
C. is inactive against gram-positive organisms.
D. cannot show synergism with an aminoglycoside.
E. penetrates better through the outer membranes of many gram-negative bacteria.
5. A 15-day-old male infant has a fever and has been crying nonstop overnight. He vomited after breastfeeding. He was born by vaginal delivery after an uncomplicated pregnancy to a healthy mother with no history of infectious diseases. The infant's nasopharynx was inflamed, and mild nuchal rigidity was noticed. The infant's white blood count is elevated, and a urinalysis is normal. Gram stain of the cerebrospinal fluid reveals small gram-positive bacilli. Which of the following would be the best empiric therapy for this patient?
A. Penicillin G
6. A 64-year-old man has severe abdominal pain and tenderness, as well as a fever. He is nauseous and has been vomiting. Bowel sounds are absent. A computed tomography (CT) scan of the abdomen reveals the presence of colonic diverticula and extramural air. He is admitted to the hospital and started on intravenous fluids and intravenous piperacillin and tazobactam. Why is piperacillin preferred over cefazolin for treating this patient?
A. Piperacillin is more tolerable when given intravenously.
B. Cefazolin cannot be given intravenously.
C. Piperacillin is less expensive.
D. Piperacillin has greater activity against gram-negative anaerobes.
E. Piperacillin has a longer duration of action.
7. Which antibiotic inhibits terminal cross-linking of cell wall glycopeptides?
8. A 62–year-old man presents with dyspnea, angina and dizziness on exertion. An echocardiogram reveals a calcified aortic valve with a restricted opening and diminished flow. Valve replacement surgery is recommended. Thirty minutes prior to the start of surgery, the patient receives a dose of cefazolin given intravenously. Why is cefazolin preferable to other agents for this patient?
A. First-generation cephalosporins have superior activity against gram-positive organisms.
B. The patient is likely to be allergic to penicillin.
C. Cefazolin is resistant to β-lactamases.
D. Cefazolin is cheaper than a third-generation cephalosporin.
E. Cefazolin is the only cephalosporin that can be given intravenously.
9. A patient with penicillin-resistant Streptococcus pneumoniae requires an antibiotic for effective therapy. Which of the following agents would be the best choice?
C. Isopropyl alcohol
10. An 82-year-old man who has been living at home has developed a fever with a productive cough and is having difficulty breathing. He reports having alternately sweats and chills and being tired. Auscultation reveals bronchial breath sounds and rales. Sputum culture shows penicillin-resistant Streptococcus pneumoniae. He is admitted to the hospital. Which of the following would be recommended therapy for this patient?
11. A 64-year-old man has severe abdominal pain and tenderness, as well as a fever. He is nauseous and has been vomiting. Bowel sounds are absent. A computed tomography (CT) scan of the abdomen reveals the presence of colonic diverticula and extramural air. He is admitted to the hospital and started on intravenous fluids and intravenous piperacillin and tazobactam. Why is tazobactam included in this patient's treatment?
A. To counteract the side effects of piperacillin
B. To increase the half-life of piperacillin
C. To inhibit the breakdown of piperacillin by bacterial penicillinases
D. To enhance the excretion of toxic metabolites of piperacillin
E. To buffer the pH of piperacillin to prevent metabolic acidosis
12. When their sensitivity has been tested in the laboratory, staphylococcal strains that are clinically resistant to vancomycin have been found to have minimal inhibitory concentrations (MICs) that are the same as vancomycin susceptible strains, but the resistant strains have very high minimal bactericidal concentrations (MBCs). These data indicate that the vancomycin resistance of these strains is most likely due to which of the following?
A. Altered penicillin-binding proteins
B. Reduced accumulation of vancomycin
C. Increased efflux of vancomycin
D. Decreased ability of vancomycin to block peptidoglycan synthesis
E. Decreased dependency of the bacterium on folic acid
13. A 38-year-old bank branch manager noticed a small pimple on her left finger that increased in size in a span of 3 hours. She reports to a medical clinic that drains it and does a bacterial culture of the fluid. Empiric antibiotic therapy is started with a cephalosporin. The culture indicates the presence of methicillin-resistant Staphylococcus aureus (MRSA). The patient's antibiotic is changed to vancomycin. What is the reason for changing the patient's antibiotic?
A. Vancomycin is the most potent cephalosporin that can be given orally.
B. Vancomycin is less likely to produce diarrhea than a cephalosporin.
C. Vancomycin inhibits bacterial cell wall synthesis at a different step from β-lactam antibiotics.
D. Vancomycin is less expensive than the cephalosporin she was taking.
14. A relatively high incidence of pseudomembranous colitis occurs with
E. nalidixic acid
15. An antibiotic-resistant plasmid enters a Pseudomonas aeruginosa cell. This plasmid carries a β-lactamase gene and an aminoglycoside phosphotransferase gene. Which one of the following would be an effective antimicrobial agent against this cell?
16. A woman presents with urethritis. A culture has revealed the organism to be Neisseria gonorrhoeae, which was sensitive to penicillin G, ampicillin, spectinomycin, tetracycline, and erythromycin. The patient is 4 months pregnant and has previously had a severe hypersensitivity reaction to oxacillin. Which of the following drugs would be indicated for this patient?
E. A cephalosporin
17. Which of the following may cause erosion of cartilage?
D. Penicillin G
18. A 29-year-old woman has dysuria, increased frequency of urination, and urgency to urinate. A urine sample is yellow and cloudy. Dipstick urinalysis gives a pH of 5.0 and is positive for leukocyte esterases, nitrites, and blood. What is the rationale for prescribing for this pateint a combination drug containing sulfamethoxazole and trimethoprim?
A. Neither drug alone has an antibacterial action.
B. The combination has a synergistic antibacterial effect.
C. Trimethoprim prevents the development of sulfa drug allergies.
D. Sulfamethoxazole traps trimethoprim in the urine.
E. Sulfamethoxazole has a short half-life, and trimethoprim has a longer duration of action.
19. A 24-year-old woman with a history of epilepsy presents with a cough, weight loss, and night sweats. Her chest radiograph (Xray) shows cavitary lesions in the upper left lobe of her lung. A sputum smear reveals many acid-fast bacilli. She is admitted to the hospital, put in a negative pressure room, and placed on a combination of isoniazid, rifampin, pyrazinamide, ethambutol, and vitamin B6. What would be the reason for including B6 in her regimen?
A. To increase bacterial uptake of the drugs
B. To prevent central nervous system effects of isoniazid
C. To inhibit gastrointestinal side effects of the drugs
D. To inhibit bacterial resistance
E. To decrease the night sweats
20. What is the usual dose-limiting adverse effect of the antitubercular drug ethambutol?
B. Bone marrow depression
C. Loss of visual acuity
D. Central nervous system toxicity
21. Hand disinfectant dispensers are commonly found in hospitals, doctors’ offices, and many public places. Which of the following ingredients is active against vegetative bacteria, Mycobacterium tuberculosis, many fungi and lipophilic viruses?
C. Isopropyl alcohol
22. A 63-year-old man had a sharp, burning, intermittent pain in his left lower back for 3 days. He has now developed a rash in the area that was painful. The rash consists of rose-colored macules with clusters of vesicles and is restricted to a band along his back. There are no symptoms suggesting genitourinary or gastrointestinal involvement. Which of the following agents might be useful for treating this patient's symptoms?
C. Penicillin V
23. Which of the following, when administered to susceptible individuals, will reduce the incidence and/or severity of influenza types A and B disease?
24. A 28-year-old man has a fever, headache, and chills, accompanied by joint and muscle aches and pains. Because seasonal influenza has been prevalent in the area, he is given zanamivir for inhalation. How does this drug prevent virus particle aggregation and release?
A. Inhibits influenza neuraminidase
B. Inhibits influenza DNA polymerase
C. Acts as an ion channel blocker of the influenza M2 protein
D. Inhibits influenza reverse transcriptase
E. Inhibits influenza protease
25. Ribavirin inhibits the replication of which of the following viruses?
A. Rubella viruses
C. Respiratory syncytial virus
D. Human immunodeficiency virus
26. Which of the following is most likely to impair renal function?
C. Amphotericin B
27. Which one of the following is the drug of choice in acute amebic dysentery?
E. Diloxanide furoate
28. Which of the following is administered for 2 weeks after patients leave an endemic malarial area to eradicate hepatic forms of the parasite?
29. A 29-year-old woman being treated for cystitis with a combination drug containing sulfamethoxazole and trimethoprim has a vaginal discharge with itching. Although her dysuria has improved, she now has a thick, curdlike, white discharge from her vagina. There is no cervical discharge or tenderness, and the uterus and adnexa are normal. Which of the following agents may be useful for treatment of this patient?
A. Topical miconazole
B. Oral penicillin
C. Oral metronidazole
D. Oral terbinafine
E. Topical terbinafine
30. A woman who was born in the United States travels frequently to Pakistan to visit friends and relatives. Her last visit there was 9 months ago. She has had a fever with sweating, malaise, joint pain, and severe headache. Thin-film Giemsa-stained blood smear shows Plasmodium vivax schizonts. The patient is given a drug that accumulates within the acidic vacuoles of blood schizonts and inhibits the polymerization of heme released from digested hemoglobin. Which of the following drugs was she given?
Answers and Explanations
1. C Transfer of drug-resistant genes usually occurs via plasmids (p. 283).
2. C The symptoms are indicative of a group A β-hemolytic streptococcus infection. Penicillin is the antibiotic of choice for group A β-hemolytic streptococcal pharyngitis. Thus, the patient must be evaluated for penicillin allergy prior to beginning therapy. Obtaining a comprehensive patient history is the most practical way to reveal a penicillin allergy (p. 289).
3. D Penicillin is effective primarily against gram-positive organisms (e.g., streptococci). Penicillin V is acid stable, so it can be taken orally (p. 289).
A Erythromycin is a second-line agent for S. pneumoniae.
B Cefazolin is also effective against many gram-positive cocci, but it is not effective orally.
C Amoxicillin is an extended spectrum penicillin and is active against S. pneumoniae, but it should not be used for the treatment of streptococcal infections when a natural penicillin would be effective.
E Piperacillin is also an extended spectrum agent, but it is not effective orally and is not being recommended for the treatment of streptococcal infections when a natural penicillin would be effective.
4. E Ampicillin is an “extended spectrum” penicillin. It differs from penicillin G, which is effective primarily against gram-positive organisms, by also being active against some gram-negative organisms, that is, by being able to more easily penetrate the gram-negative bacteria (p. 290).
5. B The most common causes of meningitis in neonates are Listeria and group B Streptococcus. The symptoms with either bacteria are similar. When the disease presents 2 to 3 weeks postpartum, it is most likely to result from exposure to Listeria during or shortly after delivery. Treatment of Listeria meningitis is with ampicillin plus or minus gentamicin because of the resistance of Listeria to cephalosporins, which are commonly chosen as empiric therapy for streptococcal meningitis in children (p. 291).
6. D The patient has diverticulitis. Piperacillin has greater activity than cefazolin against gram-negative anaerobes likely to be involved in the inflammation (p. 292).
7. B Cephalosporins inhibit bacterial cell wall synthesis in a manner similar to that of penicillin (p. 292).
A, C Streptomycin, chloramphenicol, and lincomycin inhibit bacterial protein synthesis.
D Sulfamethoxazole, a sulfonamide, is structurally similar to p-amino benzoic acid (PABA). It blocks folic acid synthesis in microbes that must synthesize folic acid from PABA.
8. A Cefazolin is a first-generation cephalosporin that has superior activity against gram-positive organisms. In this case, it is being used to prevent infection, particularly endocarditis, during the surgery (p. 292).
9. A Third-generation cephalosporins have a further increased activity against gram-negative organisms. The parenteral third-generation cephalosporins ceftriaxone and cefotaxime have excellent activity against most strains of S. pneumoniae, including the vast majority of those resistant to penicillin (p. 293).
B–E The other agents listed would not be effective.
10. B. Cefotaxime, a third-generation cephalosporin, has excellent activity against most strains of S. pneumoniae, including the vast majority of those resistant to penicillin, and is given by injection (p. 293).
A Amikacin is an aminoglycoside antibiotic that is primarily used for the treatment of serious bacterial infections.
C, D Doxycycline, a tetracycline, and cephalexin, a first-generation cephalosporin, are not indicated for this patient.
E Because the patient's infection is penicillin-resistant, ampicillin would not be appropriate.
11. C Tazobactam is a β-lactamase inhibitor that prevents the breakdown of piperacillin (p. 295).
12. D Vancomycin's effectiveness depends on its ability to inhibit bacterial cell wall synthesis. Resistance is most likely due to a decreased ability of vancomycin to block peptidoglycan synthesis (p. 295).
A Because vancomycin acts at a different step from β-lactam antibiotics, it does not depend on penicillin-binding proteins.
B, C The fact that the MICs are the same indicates that the amount of vancomycin in the cells is the same; thus there is not a reduced accumulation or increased efflux of vancomycin.
E Vancomycin does not act through the folic acid pathway.
13. C Methicillin-resistant Staphylococcus aureus (MRSA) is a Staphylococcus aureus infection that is resistant to treatment by β-lactam antibiotics e.g., methicillin, penicillin, amoxicillin, and some cephalosporins. Thus, the patient is changed to vancomycin, a drug that is not a β-lactam antibiotic (p. 289).
14. A Clindamycin, like many antibacterial agents, alters the normal flora of the colon, which may lead to overgrowth of Clostridium difficile. Proliferation of drug-resistant C. difficile produces two toxins that may cause pseudomembranous colitis. The antibiotics that most commonly produce pseudomembranous colitis are ampicillin and clindamycin. The disease is treated by discontinuing ampicillin or clindamycin and giving either metronidazole or vancomycin (p. 299).
B–E The other agents listed typically do not produce pseudomembranous colitis.
15. A β-lactam and aminoglycoside antibiotics would be ineffective against this cell. Tetracycline is the only agent listed that is not a β-lactam or aminoglycoside (p. 299).
B, C Gentamicin and neomycin are aminoglycosides.
D, E Ampicillin and cephalothin are β-lactam antibiotics.
16. A Spectinomycin is used for treatment of gonorrhea (p. 302).
B, E Tetracycline and erythromycin are not for use in pregnant women.
D, E The patient is allergic to penicillins, such as ampicillin, and is also likely to be allergic to cephalosporins.
17. A Ciprofloxacin is a fluoroquinolone antibiotic. Fluoroquinolones are associated with an increased risk of erosion of cartilage (p. 303). B–E The other drugs are not typically associated with cartilage damage.
18. B The combination is used because the drugs exert synergistic antibacterial activity. Sulfamethoxazole inhibits bacterial folic acid synthesis by competing with para-aminobenzoic acid, and trimethoprim inhibits dihydrofolate reductase, thus blocking two consecutive steps in the synthesis of nucleic acids and proteins essential to bacteria (pp. 303 and 311).
A Each drug alone does have some antibacterial activity.
C Trimethoprim does not prevent the development of sulfa drug allergies.
D, E Sulfamethoxazole does not trap trimethoprim in the urine, and the half-lives of the drugs are about equal.
19. B Isoniazid reacts chemically with pyridoxal and can cause neuropathy and convulsions. This is usually not a problem in patients receiving adequate vitamin B6 in the diet, but this patient has a history of seizures. Thus, coadministration of vitamin B6 is used to avoid potential adverse neurologic effects (p. 309).
20. C Ethambutol is usually well tolerated, but retrobulbar neuritis (a visual field defect) is seen occasionally at high doses (p. 309).
A, B, D, E, The other conditions are not associated with ethambutol administration.
21. C Isopropyl alcohol is the active antimicrobial agent in many hand disinfectants (p. 312).
A, B, E Cephalosporins, penicillin, and isoniazid are systemic antibiotics not found in hand disinfectants.
D Glycerin is found in soaps and lotions and is used to attract moisture.
22. A The symptoms are indicative of a herpes zoster flare-up, or shingles. Acyclovir is an antiviral drug that is effective in the treatment of herpes (p. 314).
A Amantadine is an antiviral drug used in the prophylaxis and treatment of influenza A.
C Penicillin V is a β-lactam antibiotic that is effective in mild to moderate streptococcal, staphylococcal and pneumococcal infections, such as skin, ear, and respiratory infections.
D Cefazolin is a first generation cephalosporin that is effective against many gram-positive cocci.
E Rifampin is active against tuberculosis and other microbes.
23. C Oseltamivir is an inhibitor of influenza neuraminidase and acts on both influenza types A and B. Without neuraminidase, the hemagglutinin of the virus binds to sialic acid, forming clumps and preventing virus release (p. 318).
A Trifluridine is effective against herpes simplex keratitis.
B Ribavirin is effective against respiratory syncytial virus and hepatitis C.
D Interferon-alfa is used to treat hepatitis B and hepatitis C (in combination with ribavirin).
E Gancyclovir is used to treat cytomegalovirus infection in immunocompromised patients
24. A Zanamivir inhibits influenza neuraminidase. Without neuraminidase, the hemagglutinin of the virus binds to sialic acid, forming clumps and preventing virus release (p. 318).
25. B Ribavirin is administered by aerosol to treat lower respiratory tract infections caused by respiratory syncytial virus (p. 319).
26. C Of the drugs listed, amphotericin B is the one most likely to have renal side effects (p. 324).
A Flucytosine is most likely to have hematological side effects.
B Griseofulvin may cause gastrointestinal disturbances, central nervous system abnormalities, and skin rashes.
D Ketoconazole may cause fatal hepatic toxicity, and adverse cardiac events when taken with terfenadine, astemizole, or cisapride.
E Terbinafine may cause a hypersensitivity rash, increased liver enzymes or liver failure (rarely).
27. D Metronidazole is used to treat systemic and intestinal forms of amebiasis (p. 327).
A Chloroquine is an antimalarial agent.
B Iodoquinol is only used for intestinal amebiasis.
C Dehydroemetine is an investigational drug available from the U.S. Centers for Disease Control and Prevention.
E Diloxanide is an antiprotozoal drug not currently available in the United States.
28. D Primaquine can destroy exoerythrocytic, liver-lurking forms of the parasite and is gametocidal (p. 329).
A Mefloquine is effective against erythrocytic forms and not on liver forms of the parasite.
B,C Chloroquine and quinine kill erythrocytic forms but are not effective on liver forms of the parasite.
E Pyrimethamine inhibits erythrocytic and exoerythrocytic forms of the parasite.
29. A The patient has vulvovaginal candidiasis. Alteration of the normal flora by the systemic antibiotics likely contributed to the emergence of the Candida infection. Usually a topical antifungal agent such as miconazole is effective (p. 324).
B, C Penicillin and metronidazole are antibiotics agents that are unsuitable for fungal infections.
D, E Terbinafine is used to treat onychomycosis (nail infections).
30. B Chloroquine accumulates within the acidic vacuoles of blood schizonts and inhibits the polymerization of heme released from digested hemoglobin (p. 329).