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Page No. : 59-71

ABSTRACT

Milk and milk products are important source of verotoxin-producing Escherichia coli (VTEC) which has assumed significance as zoonotic foodborne pathogen in recent years due to its life threatening human diseases. In the present investigation, isolation rate of E. coli was highest in raw milk products (38.88%) followed by milk (37.50%) and ready-to-eat milk products (21.15%). Majority of VTEC isolates (63.63%) from milk and milk products were positive for vt2 gene. According to source the highest prevalence of vt2 gene was found in ready-to-eat milk products (27.27%) followed by raw milk products (14.28%) and milk (12.50%). Good correlation was observed between vt2 gene positivity and vero cell cytotoxicity assay.
Detection for enterohaemolysin production by all the 42 E. coli isolates revealed 2 (4.76%) isolates to be phenotypically positive for E-hly. Interestingly, both enterohaemolytic strains were also positive by verocytotoxicity assay and vt2 gene. Antibiogram of all the 42 E. coli isolates against 16 different antimicrobial agents revealed highest sensitivity to netillin (97.61%) and resistance to amoxicillin, cephalothin, novobiocin, erythromycin and vancomycin (100% each). Among VTEC, highest sensitivity was observed for amikacin, norfloxacin, netillin and ofloxacin (100% each), besides these ciprofloxacin, oxytetracycline and nalidixic acid were also effective against VTEC. The highest resistance was recorded for amoxycillin, cephalothin, erythromycin, novobiocin and vancomycin (100% each). Resistance against bacitracin was also recorded.
Furthermore, another matter of concern was that all of the E. coli strains (42) showed multiple drug resistance to more than 4 drugs, while 80% VTEC were found to be resistant to 6 or more than 6 antibiotics. This alarms careful choice and use of antibiotics in VTEC infection. The study has shown high prevalence of multi drug resistant E. coli in milk and milk products, which poses public health hazard. The work shows the need for regular monitoring of milk and milk products for VTEC and their antibiogram.

Keywords: Escherichia coli, milk, polymerase chain reaction, verotoxic