Background. Extended-spectrum β-lactamase-producing organisms causing urinary tract infections are increasing in incidence and pose a major impendence to health-care facility, having limited therapeutic options. This study aimed to assess the prevalence of ESBLs in Enterobacteriaceae isolates causing urinary tract infections in Gaza strip, Palestine, and to characterize β-lactamase types and associated resistance genes. Methods. Eighty-five Enterobacteriaceae isolates were recovered from urinary tract infections within three months in Gaza Strip hospitals. The characterization of β-lactamase genes and the genetic environments of CTX-M, the identification of associated resistance genes, and the presence and characterization of integrons were tested by PCR and sequencing. Results. The occurrence rate of ESBL among tested isolates was 30 (35.3%), and among ESBL-positive isolates, blaCTX-M was the highest followed by blaTEM. ESBL-CTX-M-1 group was confirmed in 93.3%, and the remaining carried CTX-M-9 group. CTX-M-15, CTX-M-3, CTX-M-1, CTX-M-14, CTX-M-27, and CTX-M-37 enzymes were demonstrated among the isolates with the majority (73%) being CTX-M-15. ISEcp-1 was demonstrated in 27 (90%, high incidence) of ESBL isolates. Class 1 integrons have been detected in higher rates (53.3%) in ESBL-positive isolates in comparison with non-ESBL isolates (6, 33.3%). Cassettes of integron-1 contain (aadA1, aadA2, aadA5, dfrA5, dfrA7, dfrA12, and dfrA17) genes. The aac(6′)-Ib-cr gene was demonstrated in 36.7% of ESBL-positive isolates. Conclusions. This study indicates that blaCTX-M-15 was the most prevalent β-lactamase in this region. Our study demonstrates for the first time in Palestine the identification of blaCTX-M-15 in P. rettgeri and S. liquefaciens, also blaCTX-M-37 in E. cloacae. The coexpression of multiple β-lactamase genes with aac(6′)-Ib-cr and qnr in the presence of ISEcp-1 and integrons in individual strains will increase the dissemination of highly resistant strains. ESBL producers were more resistant than non-ESBLs producers for almost all tested antibiotics.
