Serotypes of sorbitol-positive shiga toxigenic Escherichia coli (SP-STEC) isolated from freshwater fish

Abstract

A total of 104 strains of Escherichia coli isolated from the intestinal contents of freshwater fish (Catla catla) (n=150) were subjected for virulence characterization by multiplex PCR. One or more virulence genes were detected in a total of 18 (17.3%) isolates viz., shiga-toxin type-1 (stx1) in 18 (17.3%) isolates, intimin (eaeA) in eight (7.6%) isolates, shiga-toxin type-2 (stx2) in four (3.8%) isolates and entero-hemolysin (hlyA) in four (3.8%) isolates. All the 18 isolates have shown pink colonies on Sorbitol-MacConkey agar (SMAC) indicative of sorbitol fermenting non-O157 serotype. Serotyping was performed to identify sorbitol positive (SP)-shiga toxigenic E. coli (STEC) isolates. Diverse serotypes of SP-STEC detected include O120 (three isolates), O141 (two), O63 (two), rough (two) and O126 (one), whereas eight isolates were found to be ‘O’ group untypable (UT). This was the first report on the detection of SP-STEC serotypes from freshwater fish in Andhra Pradesh, India.