Survival of enterococcal and streptococcal species in natural waters

Survival capabilities of indicators of fecal pollution, such as enterococci, in the natural aquatic environment are of particular importance in proper management of a watershed. The Las Vegas Wash (LVW) is a naturally occurring and engineered tributary to Lake Mead; The ability of the Las Vegas Wash to sustain microbial viability over time was assessed utilizing ATCC cultures and environmentally isolated species. Wash water samples were autoclaved and seeded with known concentrations of enterococci. Microcosms were incubated at 25°C, and decline was measured by heterotrophic plate counts at specific time intervals. Results of survival studies using ATCC derived species showed that the Wash could sustain microbial viability over extended periods of time, with the longest-lived species, E. faecium, surviving 74 days. Some isolates, however, were not able to persist in the oligotrophic environment of the wash and were not able to sustain viable cell counts past three weeks. (Abstract shortened by UMI.)