Development of resistance by Enterobacter cloacae during therapy of pulmonary infections in intensive care patients.

The emergence of resistance during therapy and the efficacy of different antibiotic therapy regimens were studied in 38 intensive care patients suffering from pulmonary infections caused by Enterobacter cloacae. Every three days a fresh isolate was obtained from each patient and tested in vitro for susceptibility to 16 antibiotics by determination of the minimal inhibitory concentrations. During therapy with cefotaxime and tobramycin the E. cloacae strains from 47% of the patients became resistant to cefotaxime within 6 days. In all cases resistance encompassed all other broad-spectrum penicillins and cephalosporins tested, as well as aztreonam. Development of resistance regularly led to persistence of bacteria. Resistance to tobramycin, ciprofloxacin or imipenem was not observed. Treatment of 25 patients with persisting E. cloacae infections was successful in 17 out of 18 patients treated with imipenem and in 6 out of 7 patients receiving ciprofloxacin.