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Chapter 51: Clinical Use of Antimicrobial Agents

A hospitalized AIDS patient is receiving antiretroviral drugs but no antimicrobial prophylaxis. He develops sepsis with fever, suspected to be caused by a Gram-negative bacillus.

Antimicrobial treatment of this severely immune-depressed patient should not be initiated before

(A) Antipyretic drugs have been given to reduce body temperature

(B) Infecting organism(s) have been identified by the microbiology laboratory

(C) Results of a Gram stain are available

(D) Results of antibacterial susceptibility tests are available

(E) Specimens have been taken for laboratory tests and examination

To delay therapy until laboratory results are available is inappropriate in serious bacterial infections, but specimens for possible microbial identification must be obtained before drugs are administered. The answer is E.

A hospitalized AIDS patient is receiving antiretroviral drugs but no antimicrobial prophylaxis. He develops sepsis with fever, suspected to be caused by a Gram-negative bacillus.

If amikacin is used in the treatment of this patient, monitoring of serum drug level may be advised because the drug

(A) Does not penetrate into cerebrospinal fluid

(B) Has a narrow therapeutic window

(C) Is antagonized by beta-lactam antibiotics

(D) Is hematotoxic

(E) Is rapidly metabolized by the liver

Monitoring plasma aminoglycoside levels is important because amikacin and other aminoglycosides have a low therapeutic index; toxicity may occur when plasma levels are only 3–4 times higher than minimum inhibitory concentrations. Decreases in renal function may elevate the plasma levels of aminoglycosides to toxic levels within a few hours. Aminoglycosides undergo renal elimination and they are not hematotoxic. The answer is B.

A hospitalized AIDS patient is receiving antiretroviral drugs but no antimicrobial prophylaxis. He develops sepsis with fever, suspected to be caused by a Gram-negative bacillus.

A combination of drugs might be given to this patient to provide coverage against multiple organisms or to obtain a synergistic action. Examples of antimicrobial drug synergism established at the clinical level include the treatment of

(A) Cryptococcal meningitis with amphotericin B and flucytosine

(B) Coliform infections with sulfamethoxazole and trimethoprim

(C) Enterococcal infections with rifampin and vancomycin

(D) Pseudomonal infections with carbenicillin and gentamicin

(E) All of ...

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