ANTIMICROBIAL RESISTANCE,SEROLOGICAL AND MOLECULAR CHARACTERIZATION OF ENTEROPATHOGENIC E. COLI K99 ISOLATED FROM NEWBORN CALVES SCOURS

This study highlights the significance of E. coli infection, the most prevalent bacterial disease causing diarrhoea in calves, the rise of multidrug-resistant strains, and the threat it poses to the bovine industry, particularly in developing countries. This study aimed to isolate and identify E. coli with their antibiogram and virulence gene detection. A total of 50 faecal samples were collected from diarrheic calves at Assiut Governorate. A total of 33 E. coli (66%) was isolated. Eight different antibiotic groups were tested. All the E. coli isolates (100%) were multidrug-resistant, such as ampicillin, amoxicillin, amoxicillin-clavulanic, cefotaxime, and rifampin. All E. coli isolated were 100% sensitive to norfloxacin and trimethoprim-sulfamethoxazole. Biofilm formation was confirmed in 30 isolates (90.9% of total pathogens, 60.0% of total samples) using the Congo red agar method. Serological identification of E. coli revealed the presence of O128:H21 (K99) (6) strains, O101 (K99) (4), O128:H2 (4), and O26:H11 (3), predominantly belonging to enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC), and enterohemorrhagic E. coli (EHEC). Serologically, K99 was exhibited in 13 isolates out of 30 (43.3%). Five of the 11 isolates positive for the K99 gene were positive for stx2, hlyA, blaTEM, ampC, and fimH, while three isolates were positive for stx1, eaeA, and blaCTX-M. The results demonstrated that genotypic detection of the biofilm virulence gene (fimH) was consistent with phenotypic detection of biofilm formation in multidrug-resistant isolates. In conclusion, these findings suggest that multidrug-resistant and virulent strains of E. Coli K99 play a role in calf scours and continuously emerge, posing serious threats to human and animal health. Antimicrobial susceptibility testing should be done regularly on drugs that are commonly used.