National surveillance of antimicrobial susceptibility of CTX-M-positive and -negative clinical isolates of Escherichia coli from Kuwait government hospitals

Abstract

Antibiotic resistance in Escherichia coli is becoming a complex therapeutic problem. Surveillance programs are valuable tools and offer important information on bacterial resistance trends. This study was undertaken to determine the susceptibility of clinically significant isolates of E. coli obtained from patients admitted to 8 Kuwait government hospitals and to examine how this was influenced by the production of CTX-M extended-spectrum beta-lactamases (ESBLs). The susceptibility of 876 consecutive clinically significant strains of E. coli to 13 antibiotics was determined by Etest. ESBL production was assessed by ESBL-Etest method and the presence of CTX-M beta-lactamases was confirmed by PCR technique. Of the 876 isolates, 604 (69%) were highly non-susceptible to ampicillin with MIC(90 )of >256 microg/ml. Resistance to the 3(rd)-generation cephalosporins ranged from 7.5% in the Maternity hospital to 29% in the Ibn Sina hospital; ciprofloxacin resistance rates ranged from 14% and 40%, respectively. Carbapenems and amikacin demonstrated excellent activity. The minimum inhibitory concentrations (MIC(90)) of cefotaxime, ceftazidime, cefepime and ciprofloxacin were >256, 64, >256 and >32 microg/ml, respectively for CTX-M-positive isolates versus 0.5, 1, 025 and 0.125 microg/ml for CTX-M-negative strains. Frequencies of CTX-M-positive isolates within the cefotaxime MIC ranges of 1-2, 3-8, 9-16 and >16 microg/ml were 0, 4, 15 and 81%, respectively. In conclusion, the susceptibility of E. coli to the 3(rd )generation cephalosporins and ciprofloxacin was influenced by the presence of CTX-M ESBL and a high proportion of the CTX-M-producing isolates were in the susceptibility ranges of cefotaxime.