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

Background: The prevalence of extended-spectrum β-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 μg) and a combination of ceftazidime/clavulanate (30/10 μg) disks with a ≥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 μg/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.