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Chapter 43: Beta-Lactam Antibiotics & Other Cell Wall- & Membrane-Active Antibiotics

JT is a 14-year-old patient who is diagnosed with otitis media and is prescribed amoxicillin. She returns 72 hours later with no signs of improvement, which suggests that the bacteria causing the infection is resistant to amoxicillin. Which of the following could be added to the treatment plan to combat this resistance?

(A) Beta-lactamase inhibitors (eg, Clavulanate)

(B) Cephalosporins (eg, Cefepime)

(C) Carbapenems (eg, Meropenem)

(D) Monobactams (eg, Aztreonam)

Penicillins bind to PBPs, which act at the transpeptidation stage of cell wall synthesis (the final step), and inhibit peptidoglycan cross-linking. Cephalosporins, carbapenems, monobactams, and other penicillins act similarly. JT’s resistance to amoxicillin may be due to increased bacterial production of beta-lactamases, so addition of a beta-lactamase inhibitor will increase the efficacy of amoxicillin. The answer is A.

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.

The most appropriate treatment of gonorrhea in this patient is

(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

Treatments of choice for gonorrhea include a single dose of ceftriaxone (intramuscularly). Because of the high incidence of beta-lactamase-producing gonococci, the use of penicillin G or amoxicillin is no longer appropriate for gonorrhea. Alternative drugs (not listed) for gonorrhea include cefixime, azithromycin (see Chapter 44) or spectinomycin (see Chapter 45). The answer is A.

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.

Immunofluorescent microscopic examination of fluid expressed from the penile chancre of this patient revealed treponemes. Because he appears to ...

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