Fate of Salmonella in Central Florida Surface Waters and Evaluation of EPA Worst Case Water as a Standard Medium

Abstract

Salmonella persistence in sterile surface water, nonsterile surface water, or deionized water over 336 days was explored. The suitability of EPA (U.S. Environmental Protection Agency) Worst Case water as a standard medium was also evaluated. Salmonella was enumerated by spread plating or most probable number at set time points after inoculation into water (sterile and nonsterile surface, deionized, and EPAWorst Case waters) and held at 15, 21, or 288C. Total coliforms from nonsterile waters were enumerated by spread plating. Salmonella decreased most rapidly in nonsterile surface water. Addition of cycloheximide to nonsterile surface waters did not increase Salmonella survival compared with the same nonsterile surface water without cycloheximide except for the water held at 158C. Total coliform populations decreased to below the limit of detection at 112 days; Salmonella remained detectable throughout the entire 168-day experiment. Salmonella populations persist at least 336 days in all waters tested; coliforms remained detectable to 112 days. Rates of decline (time required for a 1-log reduction) in nonsterile waters were at least five times shorter than those of other water types. EPAWorst Case water is a suitable standard for surface water microcosms. This study adds to the limited knowledge regarding Salmonella survival in surface waters. It demonstrates the potential long-term survival of Salmonella in fresh water and the importance of biotic factors when designing microcosm-based experiments. © International Association for Food Protection. HIGHLIGHTS • Survival of Salmonella was studied in surface waters. • Salmonella stayed alive in nonsterile microcosms for 168 days. • Limited decline was seen in sterile surface, deionized, and EPA Worst Case water. • EPA Worst Case water offers potential as a standardized medium.