Survival and regrowth of fecal enterococci in desiccated and rewetted sediments

Abstract

Fecal enterococci are bacteria widely used as indicators of fecal contamination in marine and estuarine waters. One assumption is that these bacteria do not persist or regrow in the environment. Our continuing problems with high numbers of fecal enterococci in sediment suggested that these bacteria may persist and regrow. Therefore, we conducted experiments with fecal enterococci to determine their ability to survive desiccation and to regrow in marine and estuarine sediments from Georgia, New Hampshire, and Puerto Rico after 0, 2, 30, and 60 days. Although numbers of fecal enterococci generally decreased with increased length of drying, many fecal enterococci survived desiccation and regrew in rewetted sediment, violating the assumption that fecal bacteria not persist or regrow in the environment. Because there is not a better alternative to fecal enterococci as fecal indicator bacteria, these results suggest that care should be taken not to disturb the sediment when sampling water for fecal contamination, or if the sediment is already disturbed (e.g., on windy days or during runoff conditions), then the influence of sediment should be considered.