Dairy farm investigation on Shiga toxin-producing Escherichia coli (STEC) in Kolkata, India with emphasis on molecular traits of the strains.

Abstract

An investigation was conducted to determine the distribution, virulence gene profile andphenotypes of Shiga toxin-producing Escherichia coli (STEC) strains within a dairy farm inKolkata, India by characterizing the STEC strains isolated from healthy dairy cow and calf stoolsamples, raw milk and farm floor swabs from July 2001 to March 2002. Primary screening bymultiplex-PCR detected stx1 and stx2, the common virulence genes of STEC, in 18.9 % of cowfaeces, 32.4 % of calf stool samples, 21.6 % of farm floor swabs and 4.5 % of raw milk samplesand viable STEC were recovered from 4.5, 9.9, 8.1 and 1.8% of the corresponding PCR-positivesamples. Strains harbouring stx1 (63.3 %) and hlyA (53.3 %) were frequently detected comparedto eae (13.3%). Most of the strains harboured similar sets of reported virulence genes commonamong isolates from diarrhoea patients. Most of the strains also exhibited multidrug resistance,sorbitol fermentation and produced enterohaemolysin. The randomly amplified polymorphicDNA–PCR (RAPD–PCR) profile of the STEC strains isolated from the farm milieu revealeddiverse banding patterns and clonal analysis demonstrated that the strains from different sourceswere not identical but showed some genetic relatedness. The study demonstrates the potential ofdairy farm for housing virulent STEC.

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