Molecular Characterisation of Virulence Genes and Antimicrobial Resistance in Escherichia coli Isolates from Diarrheic Ruminants

Enteric colibacillosis caused by pathogenic Escherichia coli strains remains a significant health and economic concern in neonatal ruminants, while the concurrent emergence of antimicrobial resistance poses serious public health threats. This study evaluated the prevalence of virulence genes and antibiotic resistance patterns in E. coli isolates from diarrheic lambs, kids, and buffalo calves from the Jammu region. Of 150 faecal samples collected, 123 (82%) were confirmed as E. coli. Species-wise prevalence: buffalo calves 96% (48/50), lambs 76% (38/50), kids 74% (37/50). Multiplex PCR screening revealed virulence gene distribution: hlyA 28.45% (35/123), eaeA 17.88% (22/123), stx1 15.44% (19/123), stx2 8.94% (11/123). Overall, 34.14% (42/123) of isolates harboured one or more virulence genes, with the stx1/eaeA/hlyA combination being most prevalent at 13.00%. Antibiotic susceptibility testing of 42 virulent isolates demonstrated alarming multidrug resistance: 100% resistance to Enrofloxacin, Cefoxitin, and Ampicillin; 90.24% to Cefpodoxime and Erythromycin; while Imipenem and Aztreonam retained complete sensitivity (100%). Multidrug-resistant phenotype (≥3 drug classes) was observed in 71.43% (30/42) of virulent isolates. These findings underscore the urgency of antimicrobial stewardship, enhanced surveillance, and One Health strategies to mitigate zoonotic transmission and therapeutic failures in treating colibacillosis in neonatal ruminants.