Identification of coliform genera recovered from water using different technologies

Abstract

Aims: Methods for the detection of coliforms in water have changed significantly in recent years with procedures incorporating substrates for the detection of β‐d‐galactosidase becoming more widely used. This study was undertaken to determine the range of coliform genera detected with methods that rely on lactose fermentation and compare them to those recovered using methods based upon β‐d‐galactosidase. Methods and Results: Coliform isolates were recovered from sewage‐polluted water using m‐endo, membrane lauryl sulfate broth, tergitol TTC agar, Colilert‐18®, ChromoCult® and ColiScan® for primary isolation. Organisms were grouped according to whether they had been isolated based upon lactose fermentation or β‐d‐galactosidase production. Conclusions: A wide range of coliform genera were detected using both types of methods. There was considerable overlap between the two groups, and whilst differences were seen between the genera isolated with the two method types, no clear pattern emerged. Substantial numbers of ‘new’ coliforms (e.g. Raoutella spp.) were recovered using both types of methods. Significance and Impact of the Study: The results presented here confirm that both methods based on lactose fermentation or detection of β‐d‐galactosidase activity recover a range of coliform organisms. Any suggestion that only methods which are based upon fermentation of lactose recover organisms of public health or regulatory significance cannot be substantiated. Furthermore, the higher recovery of coliform organisms from sewage‐polluted water using methods utilizing β‐d‐galactosidase‐based methods does not appear to be because of the recovery of substantially more ‘new’ coliforms.

Molecular Method for Detection of Total Coliforms in Drinking Water Samples

“…In 1914, the U.S. Public Health Service determined that the total coliform group included all aerobic and facultative anaerobic, Gram-negative, non-spore-forming bacilli that, when incubated at 35 to 37°C, ferment lactose and produce acid and gas (CO 2 ) within 48 h (8). Since then, there have been developments in the methodologies used to detect coliform organisms, but for many years the group was defined by procedures that relied upon their relative resistance to the presence of bile salts and their ability to ferment lactose with the production of acid and gas (5). However, in the past 15 years, significant changes have occurred in terms of the definition and taxonomy of the coliform group and the methods used for their detection (5).…”

“…Despite reservations about their usefulness as indicators of fecal contamination, the total coliform group remains a water quality indicator in many countries and continues to be used to some extent as a regulatory parameter (3,4). Indeed, even in situations in which fecal contamination is present, total coliforms are more numerous than E. coli, thereby representing a more sensitive indicator (5). Furthermore, some members of the total coliform group are considerably more resistant to disinfection than E. coli and are better indicators of poor disinfection (3,5).…”

“…Indeed, even in situations in which fecal contamination is present, total coliforms are more numerous than E. coli, thereby representing a more sensitive indicator (5). Furthermore, some members of the total coliform group are considerably more resistant to disinfection than E. coli and are better indicators of poor disinfection (3,5). The presence of total coliforms in a water distribution system can also indicate a lack of system integrity (6).…”

“…Additional changes in microbial taxonomy and the use of methods that recover coliforms based on the detection of ␤-D-galactosidase further increased the number of genera to include Cedecea, Yokenella, Ewingella, Leclercia, Buttiauxella, Rahnella, and Moellerella. Continuing improvements in microbial taxonomy will certainly result in more genera being included in the group known as total coliforms (5). Since the definition of the coliform group evolved in recent years, previous total-coliform-specific PCR assays as well as culture-based chromogenic methods must be evaluated in accordance with the new definition for specificity and ubiquity.…”

“…The presence of total coliforms in a water distribution system can also indicate a lack of system integrity (6). Thus, total coliform bacteria are commonly used to evaluate the general sanitary quality of water (3,5).…”