Salmonella enterica Serovar Diversity, Distribution, and Prevalence in Public Access Waters from a Central California Coastal Leafy Green Growing Region during 2011 - 2016

Contaminated produce is responsible for nearly half of all foodborne illness, with leafy green vegetables causing more than any other produce type. An avenue of potential pre-harvest contamination is irrigation or surface water exposed to fecal contamination through contact with wildlife, livestock, and raw or poorly composted manure. Non-typhoidal Salmonella enterica is among the leading causes of bacterial foodborne illness and is estimated to be one of the highest burden foodborne pathogens worldwide. The species S. enterica is extremely diverse with six subspecies and over 2,500 different serovars, with approximately 100 serovars account for most human infections. The Central California Coastal region is an area of high agricultural productivity and is the largest produce-growing region in the United States. While the bulk of irrigation in this region is done with ground water, surface waters are available to wildlife and can flood farm fields during large rain events. From October 2011 to September 2016, we conducted an extensive survey of surface waters in this region for the prevalence of Salmonella. A preliminary report from the first two years of this survey reported on 996 isolates and indicated a Salmonella prevalence of 65%. The present report includes overall and seasonal prevalence data for the entire survey as well as the serovars and geographical distribution of Salmonella recovered from 1,941 individual isolates. This study is a contribution toward understanding of Salmonella ecology in the region.