IS E. COLI A VALID INDICATOR SPECIES FOR SALMONELLA?
E. coli is typically used as the indicator species for environmental fecal contamination. However, this species serves as a relevant indicator only if its survival rate in a given environment is equal to or slightly higher than that of the bacterium of interest. Because the majority of nonhost environments appear to be dead ends for E. coli but a means to a new host for Salmonella, this premise may not always be valid. For example, Salmonella survives longer than E. coli in many nonhost environments, such as a brackish lagoon following discharge from a sewage treatment plant stabilization pond (63) and during exposure to polar aquatic conditions (93). Likewise, Salmonella was more resistant to killing by biotic factors (microbial predators or competing organisms) than E. coli in three drinking water sources in Sierra Leone (108), perhaps reflecting a difference in adhesion to protective particles. The rate of survival of Salmonella in estuarine water at temperatures below 10°C is signi
