Diversity of antibiotic-resistant Shiga toxin-producing Escherichia coli serogroups in foodstuffs of animal origin in northern India

Practical applications This study aimed to determine the diversity of antibiotic-resistant Shiga toxin-producing Escherichia coli (STEC) serogroups in 600 foodstuff samples of animal origin in the northern part of India. Of the 158 (26.33%) E. coli isolates that were detected in food samples the 'O' antigen-based serotyping revealed the abundance of serogroups O60, O86, O154, O73, O50, O8, and O68. Overall, 45 (28.4%) E. coli isolates were potentially verotoxin producers as determined by verotoxin assay and confirmed by polymerase chain reaction (PCR), of which 42.2% of the STEC isolates originated from raw beef. Among 45 STEC isolates, 51.1% harbored vt(1) gene whereas 48.9% of the serogroups carried vt(2) gene. Chi-squared test revealed significant difference (p = .001) in the prevalence of STEC serogroups in different foodstuffs. STEC serogroups showed higher resistance to nalidixic acid (71.7%) followed by ampicillin (66.6%). Multidrug resistance (i.e., resistance to 3 or more antimicrobial classes) was exhibited by 55.6% of STEC serogroups. This investigation demonstrated the diversity of STEC, particularly multidrug-resistant serogroups in various foodstuffs, which is a matter of serious concern from a public health stand point. Foodstuffs of animal origin available for human consumption in the city of Bareilly, may pose significant health threats due to contamination of various toxigenic and multidrug-resistant non-O157 STEC serogroups, and call for public health authorities to enhance surveillance/monitoring programs to prevent the spread of multidrug-resistant toxigenic non-O157 STEC serogroups in Indian communities and for better public health protection.