Multiple-Drug Resistant Shiga Toxin-Producing E.Coli in Raw Milk of Dairy Bovine in Khyber Pakhtunkhwa, Pakistan

Abstract Shiga-toxin-producing Escherichia coli (STEC) also known as verocytotoxin-producing E. coli (VTEC), strains are zoonotic pathogens and can cause severe diseases in humans, such as diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome. E. coli O157:H7 is the most well-known serotype of this group. Ruminants are the main reservoir of these bacteria and contaminated raw milk is the key source of the infection. Shiga toxin-producing Escherichia coli (STEC) is harboring, drug-resistant genes in dairy bovine raw milk samples received from street vendors, milk shops, and dairy farms in the province of Khyber Pakhtunkhwa, Pakistan. The current study was carried out to investigate the presence of various STEC strains in raw milk of dairy bovine. Out of 800 milk samples, 321 (40.5%) samples were positive for E. coli. Further investigation of E. coli through multiplex PCR for the presence of four virulence genes i.e., stx1, stx2, eae, ehxA revealed that 40 out of 321 (5.0%) positive samples were belonging to STEC strains of various serotypes and were positive for one or more virulence genes. STEC isolates were checked for their antibiotic susceptibility to 12 antibiotics and showed resistance to a range of antimicrobial agents. The highest percentages of resistance were detected for ceftriaxone (72%), Amoxicillin (68%), and penicillin (59%) followed by Augmentin (50%), and the highest susceptibility was found for Norfloxacin (54%) followed by Enrofloxacin (50%). STEC strains showed 27.5% ability to produce extended-spectrum beta-lactamase (ESBL) and genotypically presence with the bla ctxm gene. STEC strains isolated from milk, and dairy products respectively were multi-drug resistant. These results highlight the potential threat to public health and necessitate the adoption of appropriate control measures to minimize the threat.