Role of aminoglycosides in face of introduction of new beta-lactam antibiotics in treatment of nosocomial infection.

Aminoglycosides often are employed for empiric therapy of nosocomial infection because of their activity against a wide spectrum of gram-negative aerobic bacilli (GNAB). New beta-lactam antimicrobials also are active against many GNAB. As toxicity appears less likely for the beta-lactams than for aminoglycosides, their use might be preferable if susceptibility profiles were equivalent. We studied susceptibility of 90 GNAB recovered from blood culture during a three-month period. All were susceptible to aminoglycosides; 93% were susceptible to at least one of the following: ampicillin, carbenicillin, ticarcillin, cephalothin, chloramphenicol or trimethoprim-sulfamethoxazole. All were susceptible to at least one of our newer beta-lactams (cefamandole, cefoxitin, cefotaxime, moxalactam, piperacillin), but the percentage susceptible to any single beta-lactam was lower than that for any of the aminoglycosides tested. All of the isolates were susceptible to combinations of two beta-lactam drugs. In our hospital, beta-lactams may be reasonable alternatives to aminoglycosides in selected cases where susceptibility has been demonstrated. However, aminoglycosides continue to provide the broadest single-drug coverage for empiric therapy of known or suspected sepsis with GNAB. The utility of combinations of beta-lactam drugs for empiric therapy requires further assessment by clinical trials.