Salmonella enterica serovar diversity, distribution, and prevalence in public-access waters from a central California coastal leafy green-growing region from 2011 to 2016

Authors: Gorski, Lisa; LIANG, ANITA - Food Safety Inspection Service (FSIS); WALKER, SAMARPITA - Food Safety Inspection Service (FSIS); Carychao, Diana; Aviles Noriega, Ashley; MANDRELL, ROBERT - Retired ARS Employee; Cooley, Michael

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2021
Publication Date: 2/8/2022
Citation: Gorski, L.A., Liang, A.S., Walker, S., Carychao, D.K., Aviles Noriega, A., Mandrell, R., Cooley, M.B. 2022. Salmonella enterica serovar diversity, distribution, and prevalence in public-access waters from a central California coastal leafy green-growing region from 2011 to 2016. Applied and Environmental Microbiology. 88(3). Article e01834-21. https://doi.org/10.1128/aem.01834-21.
DOI: https://doi.org/10.1128/aem.01834-21

Interpretive Summary: Salmonella is one of the leading causes of bacterial foodborne illness and increasing numbers of outbreaks and recalls are due to contaminated produce. A survey of public access surface waters in a produce-growing region along the Central California Coast was conducted to determine the prevalence and diversity of Salmonella in the region. From 2011 – 2016, 2,979 samples of water/sediment were collected from rivers, lakes, streams, and ponds. Salmonella was isolated from 1,685 samples, indicating an overall prevalence of 56.6%. Higher levels of positive samples were detected in the Spring months. Salmonella was more likely to be isolated after significant rain events. Analysis of 1,936 isolates from those positive samples revealed 91 different serovars in the collection. This result indicates a high diversity of Salmonella in the region. The most common serovars were I 6,8:d:-, Give, Typhimurium, Muenchen, Oranienburg, and Montevideo. Sixteen of the 24 most common serovars detected in the region are among the serovars reported to cause the most human salmonellosis in the United States. Some of the serovars showed location bias. Pulsed field gel electrophoresis analysis of the isolates

Technical Abstract: Prevalence and serovar diversity of Salmonella enterica was measured during a five-year survey of surface waters in a 500 mi2 agricultural region of the Central California Coast. Rivers, streams, lakes, and ponds were sampled bimonthly resulting in 2,979 samples. Overall prevalence was 56.6% with higher levels detected in Spring than in Fall. Small, but significant differences in prevalence were detected based on sample locations. Detection of Salmonella was positively correlated with both significant rain events and levels of generic Escherichia coli. Analysis of 1,936 isolates revealed significant serovar diversity, with 91 different serovars detected. The most common isolated serovars were S. enterica subsp. enterica serovars 6,8:d:- (406 isolates, and potentially monophasic Salmonella Muenchen), Give (334 isolates), Muenchen (158 isolates), Typhimurium (227 isolates), Oranienburg (106 isolates), and Montevideo (78 isolates). Sixteen of the 24 most common serovars detected in the region are among the serovars reported to cause the most human salmonellosis in the United States. Some of the serovars showed location and seasonal bias. Analysis of XbaI Pulsed Field Gel Electrophoresis (PFGE) patterns of strains of serovars Typhimurium, Oranienburg, and Montevideo showed significant intra-serovar diversity. There was evidence of the same PFGE pulsotypes in the region for multiple years of the survey, indicating persistence or regular re-introduction to the region. Non-typhoidal Salmonella is the among the leading causes of bacterial foodborne illness and increasing numbers of outbreaks and recalls are due to contaminated produce. High prevalence and 91 different serovars were detected in this leafy green growing region. Seventeen serovars that cause most of the human salmonellosis in the United States were detected, with sixteen of those serovars detected in multiple locations and multiple years of the 5-year survey. Understanding the widespread prevalence and diversity of Salmonella in the region will is needed to promote food safety practices and intervention methods for growers and regulators.