COMPARATIVE STUDY OF FLUOROGENIC AND CHROMOGENIC MEDIA FOR SPECIFIC DETECTION OF ENVIRONMENTAL ISOLATES OF THERMOTOLERANT ESCHERICHIA COLI PRAMOD W. RAMTEKE ∗ and SUMAN TEWARI Environmental Microbiology Section, Industrial Toxicology Research Centre, M.G. Marg, Lucknow, India ( ∗ author for correspondence, e-mail: pwramteke@yahoo.com) (Received 23 March 2001; accepted 30 October 2001) 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 β -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. Keywords: E. coli, chromogenic medium, fluorogenic media, MPN test 1. Introduction The presence of E. coli is traditionally used for the monitoring of the microbio- logical safety of food, water supplies and recreational waters. The presence of E. coli directly relates to fecal contamination with its implied threat of the presence of enteric disease agents (Rice et al., 1990). A major limitation of the current methods used for enumerating E. coli is growth of fecal coliforms which are not exclusively of fecal origin thereby giving a false indication of the sanitary quality of water (Augoustinos et al., 1994; Ramteke et al., 1992; Ramteke, 1995). Approximately 97% of E. coli strains were found to possess the enzyme β -D- glucuronidase (GUD) and that almost all other coliforms lack this enzyme (Kilian and Bulow, 1979). Several techniques for detection of E. coli are based on en- zymatic hydrolysis of fluorogenic and chromogenic substrates for GUD (Eaton ∗ Present address: Department of Chemistry, Allahabad Agricultural Deemed University, Alla- habad, India 211007 Environmental Monitoring and Assessment 79: 121–127, 2002. © 2002 Kluwer Academic Publishers. Printed in the Netherlands.