Prevalence and Genetic Relatedness of Extended Spectrum-β-Lactamase-Producing <i>Escherichia coli</i> Among Humans, Cattle, and Poultry in Pakistan

Abstract

<b><i>Objective:</i></b> To determine the prevalence and genetic relatedness of <i>bla</i>_CTX-M-type extended spectrum-β-lactamase (ESBL)-producing <i>Escherichia coli</i> at the human-animal interface in Pakistan. <b><i>Materials and Methods:</i></b> A total of 150 human, cattle, and poultry fecal samples (50 each) were screened for ESBL-producing <i>E. coli</i> using ESBL CHROMagar^®. Bacterial species confirmation as well as determination of minimum inhibitory concentrations (μg/mL) to different antibiotics was performed using the automated VITEK^®-2 compact system. Phenotypic confirmation of ESBL production was performed according to the Clinical Laboratory Standards Institute (CLSI) guidelines. Genetic analysis of <i>bla</i>_CTX-M was carried out by PCR and DNA sequencing. Plasmids and clonal similarity of the <i>E. coli</i> strains were determined by PCR-based replicon typing and pulsed-field gel electrophoresis (PFGE), respectively. <b><i>Results:</i></b> Of 150 samples, 29 (19.3%) ESBL-producing <i>E. coli</i> were recovered, and majority of them originated from human (<i>n</i> = 16; 55%), followed by cattle (<i>n</i> = 9; 31%) and poultry (<i>n</i> = 4; 13.7%). <i>bla</i>_CTX-M-15 was predominant ESBL genotype (<i>n</i> = 25; 86.2%), mainly identified from human (<i>n</i> = 15) and cattle (<i>n</i> = 9). This is also the first report of the occurrence of CTX-M-15 and CTX-M-55 in cattle and poultry <i>E. coli</i> isolates of Pakistan, respectively. The majority of the ESBL-producing <i>E. coli</i> (96.5%) showed a multidrug resistance phenotype. All isolates carried IncFII or IncFIA plasmids, and the phylogroup B1 was dominant (44.8%) followed by phylogroups A (31%), D (17.2%), and B2 (6.8%). PFGE revealed that isolates from different hosts were genetically unrelated. <b><i>Conclusion:</i></b> Presence of CTX-M-15-type ESBL-producing <i>E. coli</i> in different reservoirs is alarming and has the potential to impact both veterinary and human therapeutic treatment options.