Beta-lactam Antibiotics (10)
- 1.The primary mechanism of antibacterial action of the penicillins involves inhibition of
- A.
Beta-lactamases
- B.
Cell membrane synthesis
- C.
N-acetylmuramic acid synthesis
- D.
Peptidoglycan cross-linking
- E.
Transglycosylation
- 2.Questions 2–3. A 33-year-old man was seen in a clinic with a complaint of dysuria and urethral discharge of yellow pus. He had a painless clean-based ulcer on the penis and nontender enlargement of the regional lymph nodes. Gram stain of the urethral exudate showed gram-negative diplococci within polymorphonucleocytes. The patient informed the clinic staff that he was unemployed and had not eaten a meal for 2 d. What is the most appropriate treatment of gonorrhoea in this patient?
- A.
A single intramuscular dose of ceftriaxone
- B.
Amoxicillin orally for 7 d
- C.
Procaine penicillin G intramuscularly as a single dose plus oral probenecid
- D.
Meropenem orally for 7 d
- E.
Vancomycin intramuscularly as a single dose
- 3.Immunofluorescent microscopic examination of fluid expressed from the penile chancre of this patient revealed treponemes. Because he appears to be infected with Treponema pallidum, the best course of action would be to
- A.
Administer a single oral dose of fosfomycin
- B.
Give no other antibiotics because drug treatment of gonorrhea provides coverage for incubating syphilis
- C.
Inject intramuscular benzathine penicillin G
- D.
Treat with oral tetracycline for 7 d
- E.
Treat with vancomycin
- 4.Which of the following statements about beta-lactam antibiotics is false?
- A.
Cephalexin and other first-generation cephalosporins do not cross the blood-brain barrier
- B.
Ceftriaxone and nafcillin are both eliminated mainly via biliary secretion
- C.
Instability of penicillins in gastric acid can limit their oral absorption
- D.
Renal tubular reabsorption of amoxicillin is inhibited by probenecid
- E.
Ticarcillin has activity against several gram-negative rods
- 5.A 36-year-old woman recently treated for leukemia is admitted to the hospital with malaise, chills, and high fever. Gram stain of blood reveals the presence of gram-negative bacilli. The initial diagnosis is bacteremia, and parenteral antibiotics are indicated. The records of the patient reveal that she had a severe urticarial rash, hypotension, and respiratory difficulty after oral penicillin V about 6 mo ago. The most appropriate drug regimen for empiric treatment is
- A.
Aztreonam
- B.
Ceftriaxone
- C.
Meropenem
- D.
Oxacillin
- E.
Ticarcillin plus clavulanic acid
- 6.Questions 6–8. A 52-year-old man (weight 70 kg) is brought to the hospital emergency department in a confused and delirious state. He has had an elevated temperature for more than 24 h, during which time he had complained of a severe headache and had suffered from nausea and vomiting. Lumbar puncture reveals an elevated opening pressure, and cerebrospinal fluid findings include elevated protein, decreased glucose, and increased neutrophils. Gram stain of a smear of cerebrospinal fluid reveals gram-positive diplococci, and a preliminary diagnosis is made of purulent meningitis. The microbiology report informs you that for approximately 15% of S pneumoniae isolates in the community, the minimal inhibitory concentration for penicillin G is 20 mcg/mL. Treatment of this patient should be initiated immediately with intravenous administration of
- A.
Amoxicillin
- B.
Cephalexin
- C.
Ceftriaxone plus vancomycin
- D.
Nafcillin
- E.
Piperacillin
- 7.Resistance of pneumococci to penicillin G is due to
- A.
Alterations in porin structure
- B.
Beta-lactamase production
- C.
Changes in chemical structure of target penicillin-binding proteins
- D.
Changes in the d-Ala-d-Ala building block of peptidoglycan precursor
- E.
Decreased intracellular accumulation of penicillin G
- 8.If this patient had been 82-years-old and the Gram stain of the smear of cerebrospinal fluid had revealed gram-positive rods resembling diphtheroids, the antibiotic regimen for empiric treatment would include
- A.
Ampicillin
- B.
Cefoxitin
- C.
Fosfomycin
- D.
Vancomycin
- 9.A patient needs antibiotic treatment for native valve, culture-positive infective enterococcal endocarditis. His medical history includes a severe anaphylactic reaction to penicillin G during the last year. The best approach would be treatment with
- A.
Amoxicillin-clavulanate
- B.
Aztreonam
- C.
Ceftriaxone
- D.
Ticarcillin
- E.
Vancomycin
- 10.Which statement about vancomycin is accurate?
- A.
Active against methicillin-resistant staphylococci
- B.
Bacteriostatic
- C.
Binds to PBPs
- D.
Hepatic metabolism
- E.
Oral bioavailability
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