Comparative study of fluorogenic and chromogenic media for specific detection of environmental isolates of thermotolerant Escherichia coli

Abstract

In a field study 78 water samples were analysed employing Fluorocult Brilla Broth (BB) and its performance was compared with standard MPN procedure. Out of 78 water samples analysed 56 (71.7%) samples yielded positive reactions in BB whereas, 50 (64.1%) samples were positive by standard fecal coliform test. A comparative study of fluorogenic and chromogenic media containing substrate beta-D glucuronide for specific detection of environmental isolates of 313 thermotolerant E. coli has been undertaken. Five fluorogenic media were used: Fluorocult MacConkey agar (MCA), Fluorocult ECD agar (ECD), Fluorocult VRB agar (VRB), Fluorocult E. coli 0157:H7 agar (ECH7) and Fluorocult Brilla Broth (BB) and Chromogenic Chromocult agar (CCA). BB and CCA were found to be highly specific and sensitive media to detect E. coli as all E. coli yielded positive reaction on them. On ECH7 and ECD agar 67.5 and 64.9 of E. coli isolates gave positive reaction, respectively. Low sensitivity was observed in case of MCA and VRB agar in detecting E. coli. The performance of BB appears to be better when compared with standard MPN procedure employing MacConkey broth/Brilliant green bile broth in detecting E. coli in drinking water.