Prevalence of class A and AmpC β-lactamases in clinical Escherichia coli isolates from Pakistan Institute of Medical Science, Islamabad, Pakistan.

In this study, 121 Escherichia coli samples isolated from clinical specimens obtained from Pakistan Institute of Medical Science, Islamabad, Pakistan, were analyzed for extended-spectrum β-lactamases (ESBLs) and AmpC β-lactamases using disk-diffusion assay and polymerase chain reaction. Of the isolates, 78 and 43 were identified as ESBL and AmpC producers, respectively. The highest resistance (89%) was observed against cefotaxime, followed by ciprofloxacin (87.6%) and cefepime (87%). Genetic analysis showed the presence of different class A and class C β-lactamase genes, either alone (44.7%) or in combination (53.6%). CTX-M (57.7%) was the most prevalent among class A, followed by TEM (20.3%) and SHV (15.4%). CIT (including LAT-1 to LAT-4, CMY-2 to CMY-7, and BIL-1) and MOX (including MOX-1, MOX-2, CMY-1, and CMY-8 to CMY-11) family-specific plasmid-mediated AmpC β-lactamases were the most prevalent among these isolates. Our study showed that both class A and class C β-lactamases contributed to cephalosporin resistance in the E. coli isolates, thereby limiting therapeutic options. Co-expression of these enzymes may further hinder the identification of ESBLs, which is a critical step for designing a successful treatment for multidrug-resistant E. coli.