2005 BES Annual Meeting Presentation and Poster Abstracts
Molecular ecology of E. coli in metro area waters
James Higgins, Sally Hornor*, Christina Hohn, and Kenneth Belt**. USDA-ARS, Beltsville, MD; *Anne Arundel Community College, Arnold, MD; **USDA Forest Service/ BES /UMBC, Catonsville, MD.
Abstract: We are interested in analyzing the genetic diversity among E. coli cultured from a variety of animal, clinical, and environmental sources, with a view towards ultimately using these data as a method of assessing water quality. Our first priority was to come up with a method capable of accurately identifying E. coli from other enteric microorganisms present in our samples; we chose to use a PCR reaction targeting the lac Z gene of E. coli. We subsequently discovered that nucleotide sequence similarities between E. coli and Enterobacter spp. occasionally require the use of an ancillary method, restriction enzyme digest, to provide a 100% specific identification protocol. Once isolates are confirmed as E. coli, they are analyzed using the triplex PCR assay described by Clermont et al. (2000) which segregates them into one of four genotypes: A, B1, B2, and D. As of mid-September 2005, 102 isolates have been genotyped; genotype B1 is most prominent at 43%, and B2 is the least prominent at 11.7%. Cow intestine isolates are either B1 or A, as are bird isolates; raccoon isolates are either B2 or D. Clinical isolates, representative of 10 different serotypes of pathogenic E. coli, are either B1 or D. Isolates collected from the urban stream Gwynns Run and the agricultural stream McDonogh have different genotyping patterns, which may reflect the differing watersheds associated with these streams. The continuous acquisition of new isolates will expand our understanding of the molecular ecology of E. coli in the metropolitan area.