|Molina, Marirosa - US-EPA|
|Fisher, Jared - US-EPA|
|Johnson, Bonita - US-EPA|
Submitted to: American Society for Microbiology Meeting
Publication Type: Abstract Only
Publication Acceptance Date: March 15, 2005
Publication Date: June 5, 2005
Citation: Molina, M., Fisher, J., Johnson, B., Jackson, C.R. 2005. Temporal variability of enterococci species in streams impacted by cattle fecal contamination. American Society for Microbiology Meeting. Q-330. Technical Abstract: Temporal variability in the gastrointestinal flora of animals impacting water resources with fecal material can be one of the factors producing low source identification rates when applying microbial source tracking (MST) methods. Understanding how bacterial species and genotypes vary over time is highly relevant when the fecal material used to create a source library is collected under very different seasonal conditions than the environmental sample. Our objective is to identify and compare the temporal variability of enterococci species in cattle manure and in streams directly impacted by cattle manure. The sites under study are located in farms where cows have unrestricted access to the streams. Enterococci were isolated monthly from water and manure samples using membrane-Enterococcus Indoxyl-*-D-Glucoside agar (mEI) as described in EPA method 1600. The isolates were identified using a multiplex PCR procedure that targets the genus and a species-specific gene (superoxide dismutase). mEI counts from the water samples indicated that May and November had the largest (725 cfu/100 ml) and lowest enterococci (71 cfu/100 ml) concentrations, respectively. Eight species were identified in cattle manure, of which E. casseliflavus (37%), faecium (22%) and hirae (18%) were the most abundant. Nine species were identified in stream samples with E. faecalis (43%), casseliflavus/flavescens (34%), and hirae (11%) being the most abundant. September exhibited the highest species abundance in manure samples while March had the highest species abundance in stream water samples. E. Asini and E. malodoratus were only detected in manure samples, but were not detected in water samples. In contrast, E. durans, gallinarum and sulfureus were only isolated from the stream samples. Cluster analysis revealed strong seasonal and spatial variability of groups of enterococci. This study suggests that in order to increase the validity of MST methods, it is necessary to consider temporal variability when constructing source libraries and designing the sampling scheme of the source material.