Detection of shiga-toxigenic Escherichia coli (STEC) in diarrhoeagenic stool & meat samples in Mangalore, India.

BACKGROUND & OBJECTIVE: Shiga-toxigenic Escherichia coli (STEC) are causative agents of bloody diarrhoea, haemorrhagic colitis (HC) and haemolytic uraemic syndrome (HUS). Humans acquire infections primarily through contaminated beef. In India, STEC has not been implicated as a major cause of diarrhoea. Hence, isolation of STEC from diarrhoeagenic stool samples of patients and beef samples marketed through retail outlets was attempted in Mangalore, India. METHODS: Diarrhoeagenic stool samples (n = 192) and meat samples (n = 103) were screened for STEC, using conventional culture methods and polymerase chain reaction (PCR) from December 2003 to 2006 in the department of Microbiology, Kasturba Medical College, Mangalore. All the E. coli isolates were subjected to antibiotic susceptibility testing and serotyping. RESULTS: Of the 40 eae positive E. coli isolates from meat sample, one was positive for all the STEC genes, namely stx1, stx2, rfb O157 and EHEC hlyA. This isolate belonged to O157 serogroup. Of the 110 eae positive E. coli isolated from stool samples, two were positive for EHEC hlyA and belonged to serogroup O8 and one was positive for bfp gene and found to be of O6 serogroup. Among the 192 stool enrichment broths tested, 160 were positive for eae gene, of which two were EHEC hlyA positive and one was bfp gene positive. Among the 103 meat enrichment cultures, 90 were positive for eae gene and one among them was positive for all the STEC genes. INTERPRETATION & CONCLUSION: Our results showed a low incidence of STEC and high prevalence of eae positive E. coli other than STEC in stool and meat samples. A low positivity was observed for PCR performed directly on stool and meat samples. However, PCR on enrichment cultures gave better results. Since E. coli O157 was isolated and detected by PCR in one of the meat samples, this organism may be of public health significance. A study on a large sample may provide some answer.