ESBL-producing Shiga-toxigenic E. coli (STEC) associated with piglet diarrhoea in India

The present study was conducted to investigate the prevalence of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli carrying other virulence genes associated with piglet diarrhoea. Faecal samples from the piglets with history of diarrhoea were processed for isolation of E. coli and were tested for their ability of ESBL production. ESBL encoding genes and other virulence genes were detected by specific PCR, and amplicons were sequenced. Ability of transferring the ESBL genes between the enteric bacteria was tested in in vitro HGT. A total of 170 E. coli was isolated, of which 43 (25.29 %) were confirmed as ESBL producer by double disc synergy test (DDST). Altogether, 6.47 and 2.94 % isolates were positive for bla TEM and bla CTX-M-15 genes, respectively, of which 2.35 % isolates were positive for both the genes and only 0.6 % isolate was positive for the bla CTX-M gene alone. The resistance traits could not be transferred to the recipient host. Based on PCR, 2 (1.18 %) and 1 (0.59 %) isolates were recorded as Shiga-toxin-producing E. coli (STEC) and enteropathogenic E. coli (EPEC), respectively. Both the STEC (one isolate positive for stx 2 and another positive for stx 2 and hlyA) isolates belonging to serogroup O2 and NT were also positive for the bla CTX-M-15 gene. This is the first report of ESBL-producing E. coli isolate possessing the STEC gene associated with piglet diarrhoea.