Pathogenicity and antibiogram of Escherichia coli isolated from diarrhoeic cow calves

Thirty two isolates of Escherichia coli recovered from diarrhoeic samples in cow calves were tested for virulence factors by a battery of in vivo (pathogenicity and enterotoxigenicity) and in vitro methods. Four isolates (12.50%) belonging to O88, O97, O98 and O159 serogroups proved fatal to Swiss albino mice on intraperitoneal inoculation of whole bacterial culture. Similarly the cell free filtrate of 4 (12.50%) isolates, belonging to O14, O88, O110 and O138 serogroups caused death of mice within 6 to 20 hours post intravenous inoculation (hpi) of intravenous inoculation. None of the isolates produced STa or LT enterotoxins in suckling mouse and mouse paw oedema test, respectively. Five (15.63%) isolates were found resistant towards the lytic action of cow calf serum, whereas 10 (31.25%) were sensitive and 17 (53.12%) intermediate sensitive to serum. The in vitro sensitivity of the isolates to antimicrobial drugs was found 100% to ciprofloxacin and sulphadiazine, followed by ceftriaxone and ceftriaxone/tazobactum (96.88%), cefotaxime (71.90%), amoxyclav (68.75%) and amikacin (46.9%).