Antibacterial susceptibility of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae and Escherichia coli.

BACKGROUND

The prevalence of extended-spectrum beta-lactamase-producing organisms and their antimicrobial resistance patterns may vary between geographic areas.

OBJECTIVES

To evaluate the prevalence and susceptibility of ESBL-producing organisms among Klebsiella pneumoniae and Escherichia coli isolated from adult and pediatric patients in two Israeli hospitals.

METHODS

ESBL production was tested according to recommendations of the Clinical and Laboratory Standards Institute, using ceftazidime (30 microg) and a combination of ceftazidime/clavulanate (30/ 10 microg) disks with a > or =5 mm difference indicating positivity. Antibiotic susceptibilities were determined by the disk diffusion method according to CLSI standards. Minimal inhibitory concentrations were determined by the E-test.

RESULTS

The prevalence of ESBL-producing organisms was significantly higher among K. pneumoniae than E. coli isolates - 32% (241/765) vs. 10% (57/547) respectively (P < 0.001), and more frequently isolated from adults than children (odds ratio 2.27 for K. pneumoniae and 12.94 for E. coli). Resistance rates for amoxicillin/ clavulanate, piperacillin-tazobactam, amikacin, and ciprofloxacin among the ESBL-producing K. pneumoniae and E. coli isolates were 95%, 82%, 49% and 77% for K. pneumoniae, and 77%, 35%, 25% and 100% for E coli. Two (0.8%) ESBL-producing and 4 (0.7%) ESBL-negative K. pneumoniae isolates showed intermediate susceptibility (MIC 6 microg/ml) to meropenem. All isolates were sensitive to ertapenem and colistin.

CONCLUSION

ESBL production among K. pneumoniae and E. coli is more prevalent in the adult population than the pediatric population and is associated with multidrug resistance.