Molecular identification of coliform bacteria isolated from drinking water reservoirs with traditional methods and the Colilert-18 system |
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| Authors: | Kämpfer Peter Nienhüser Anita Packroff Gabriele Wernicke Frank Mehling Arnd Nixdorf Katja Fiedler Stefanie Kolauch Claudia Esser Michael |
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| Affiliation: | 1. Institute of Oceanography and Fisheries, Laboratory of Microbiology, P.O. Box 500, 21000 Split, Croatia;2. Teaching Institute of Public Health of Primorje-Gorski Kotar County, Department of Environmental Health, Krešimirova 52a, 51000 Rijeka, Croatia;3. Faculty of Medicine, University of Rijeka, Department of Environmental Health, Braće Branchetta 20, 51000 Rijeka, Croatia;4. Univesity of Split, University Department of Marine Studies, Livanjska 5, 21000 Split, Croatia;5. Institute of Public Health of Istra County, Health Ecology Service, Department for Protection and Improvement of the Environment, Nazorova 23, 52100 Pula, Croatia;6. Institute of Public Health of Lika - Senj County, Department of Health Ecology, Senjskih žrtava 2, 53000 Gospić, Croatia;7. Institute of Public Health of Zadar County, Health Ecology Sevice, Department of Microbiology and Biology, Kolovare 2, 23000 Zadar, Croatia;8. Institute of Public Health of Šibenik - Knin County, Department of Ecology, Matije Gupca 95, 22000 Šibenik, Croatia;9. Teaching Institute of Public Health of Split-Dalmatia County, Department of Environmental Ecology Division of Sanitary Microbiology, Laboratory for Seawater Quality and Environmental Biology, Vukovarska 46, 2000 Split, Croatia;10. Institute of Public Health of Dubrovnik - Neretva County, Department of Environmental Health, Environmental Section, Dr. Ante Šercera 4, 20000 Dubrovnik, Croatia |
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| Abstract: | The accuracy of a traditional method (lactose utilization with acid and gas production) for the detection of coliform bacteria and E. coli was tested in comparison with method ISO 9308-1 (based on acid formation from lactose) and the Colilert-18 system (detection of beta-galactosidase). A total of 345 isolates were identified after isolation from water samples using API 20E strips. The Colilert-18 led to the highest number of positive findings (95% of the isolates were assigned to coliforms), whereas the ISO-9308-1 method resulted only in 29% coliform findings. With the traditional method only 15% were rated positive. Most of the isolates were identified by the API 20E system as Enterobacter spp. (species of the Enterobacter cloacae complex), Serratia spp., Citrobacter spp.and Klebsiella spp.; but species identification remained vague in several cases. A more detailed identification of 126 pure cultures by using 16S rRNA gene sequence analysis and analysis of the hsp60 gene resulted in the identification of Enterobacter nimipressuralis, E. amnigenus, E. asburiae, E. hormaechei, and Serratia fonticola as predominat coliforms. These species are beta-galactosidase positive, but show acid formation from lactose often after a prolonged incubation time. They are often not of fecal origin and may interfere with the ability to accurately detect coliforms of fecal origin. |
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