title: Escherichia coli and Enterococcus spp. in rainwater tank samples: comparison of culture-based methods and 23S rRNA gene quantitative PCR assays.
abstract: In this study, culture-based methods and quantitative PCR (qPCR) assays were compared with each other for the measurement of  Escherichia coli  and  Enterococcus  spp. in water samples collected from rainwater tanks in Southeast Queensland, Australia. Among the 50 rainwater tank samples tested, 26 (52%) and 46 (92%) samples yielded  E. coli  numbers as measured by EPA Method 1603 and E. coli 23S rRNA gene qPCR assay, respectively. Similarly, 49 (98%) and 47 (94%) samples yielded  Enterococcus  spp. numbers as measured by EPA Method 1600 and  Enterococcus  spp. 23S rRNA gene qPCR assay, respectively. The mean  E. coli  (2.49 ± 0.85) log(10) and  Enterococcus  spp. (2.72 ± 0.32) log(10) numbers as measured by qPCR assays were significantly (P < 0001) different than  E. coli  (0.91 ± 0.80) log(10) and  Enterococcus  spp. (1.86 ± 0.60) log(10) numbers as measured by culture-based method. Weak but significant correlations were observed between both EPA Method 1603 and the  E. coli  qPCR assay (r = 0.47, P = 0.0009), and EPA Method 1600 and the  Enterococcus  spp. qPCR assay (r = 0.42, P = 0.002). Good qualitative agreement was found between the culture-based method and the  Enterococcus  spp. qPCR assay in terms of detecting fecal pollution in water samples from the studied rainwater tanks. More research studies, however, are needed to shed some light on the discrepancies associated with the culture-based methods and qPCR assays for measuring fecal indicator bacteria.
authors.affiliation: CSIRO Land and Water, Ecosciences Precinct, 41 Boggo Road, Brisbane 4102, Australia. Warish.Ahmed@csiro.au
authors.forename: W
authors.initials: W
authors.lastname: Ahmed
authors.forename: K
authors.initials: K
authors.lastname: Richardson
authors.forename: J P S
authors.initials: JP
authors.lastname: Sidhu
authors.forename: S
authors.initials: S
authors.lastname: Toze
mesh_terms: D015373:Bacterial Typing Techniques / Q000379:methods*; D016983:Enterococcus / Q000145:classification / Q000254:growth & development* / Q000302:isolation & purification; D004926:Escherichia coli / Q000145:classification / Q000254:growth & development* / Q000302:isolation & purification; D020459:Genes, rRNA; D016133:Polymerase Chain Reaction; D011793:Queensland; D011891:Rain / Q000382:microbiology*; D014871:Water Microbiology