title: Molecular identification of coliform bacteria isolated from drinking water reservoirs with traditional methods and the Colilert-18 system.
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.
authors.affiliation: Institut für Angewandte Mikrobiologie, Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany. peter.kaempfer@agrar.uni-giessen.de
authors.forename: Peter
authors.initials: P
authors.lastname: Kämpfer
authors.forename: Anita
authors.initials: A
authors.lastname: Nienhüser
authors.forename: Gabriele
authors.initials: G
authors.lastname: Packroff
authors.forename: Frank
authors.initials: F
authors.lastname: Wernicke
authors.forename: Arnd
authors.initials: A
authors.lastname: Mehling
authors.forename: Katja
authors.initials: K
authors.lastname: Nixdorf
authors.forename: Stefanie
authors.initials: S
authors.lastname: Fiedler
authors.forename: Claudia
authors.initials: C
authors.lastname: Kolauch
authors.forename: Michael
authors.initials: M
authors.lastname: Esser
mesh_terms: D001431:Bacteriological Techniques / Q000379:methods*; D018834:Chaperonin 60 / Q000032:analysis; D016208:Databases, Factual; D004326:Drinking; D004755:Enterobacteriaceae / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D007785:Lactose / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D012336:RNA, Ribosomal, 16S; D017421:Sequence Analysis; D014871:Water Microbiology; D014881:Water Supply / Q000032:analysis*; D001616:beta-Galactosidase / Q000302:isolation & purification
chemical_list: D018834:Chaperonin 60; D012336:RNA, Ribosomal, 16S; D001616:beta-Galactosidase; D007785:Lactose