Identification of antibiotic‐resistant pathogens and virulence genes in <i>Escherichia coli</i> isolates from food samples in the Dhaka University campus of Bangladesh

Abstract

The presence of antibiotic-resistant pathogens in food is a serious public health concern nowadays. This study focuses on the isolation and characterization of potentially pathogenic <i>Escherichia coli</i> and antimicrobial-resistant pathogens in chicken curry and potato smash samples collected from the canteens and cafeteria of Dhaka University in Bangladesh. Isolates were identified by their cultural, morphological, and biochemical tests (motility indole urease test, Kliger's iron agar test, catalase test, oxidase test, methyl red and Voges-Proskauer tests). The antibiotic susceptibility test was done by the disk diffusion method. The range of total bacterial count in the potato smash and chicken curry samples was from 1.4 × 10⁴ to 1.6 × 10⁸ CFU/g and from 2.4 × 10³ to 2.6 × 10⁶ CFU/g, respectively. <i>Escherichia coli</i>, <i>Salmonella</i>, <i>Vibrio</i>, <i>Klebsiella</i>, <i>Citrobacter</i>, <i>Enterobacter</i>, <i>Proteus</i>, <i>Clostridium</i>, <i>Staphylococcus</i>, <i>Streptococcus</i>, <i>Micrococcus</i>, <i>Bacillus</i>, and <i>Sarcina</i> strains were isolated in both samples. Isolates were highly resistant to ampicillin (90.90%) followed by colistin (52.27%), azithromycin (27.27%), and tetracycline 25%. <i>Proteus</i> species had the highest rate of multiple antibiotic resistance (MAR; 62.5%), followed by <i>Citrobacter</i> species (50%). The isolated <i>E. coli</i> strains were further analyzed through PCR assay to detect virulent genes (EPEC: <i>eaeA</i> 229 bp, <i>bfpA</i> 450 bp, ETEC <i>elt</i> 322 bp, EHEC <i>hylA</i> 534 bp, and EIEC <i>ial</i> 320 bp). One <i>E. coli</i> isolate had the <i>eae</i>A target gene under EPEC pathotypes. <i>Escherichia coli</i>, as a fecal indicator, may indicate fecal contamination or poor and unhygienic food handling. The findings recommend further investigations to identify potential mechanisms of contamination and preventive measures to improve the food safety level in the canteens and restaurants.