Prevalence of Salmonella enterica Isolated from Food Contact and Nonfood Contact Surfaces in Cambodian Informal Markets

Abstract

The lack of hygiene and sanitation practices and insufficient infrastructure in Cambodian informal markets may increase the risk of food contamination, specifically raw vegetables, which in turn may increase the chances of contracting a foodborne disease. The aims of this study were i) to quantify the prevalence of Salmonella enterica based upon seasonal differences (rainy and dry) between surface types (food contact surface [FCS] and non-food contact surface [NFCS]) and between location of vendors within the market (inside and outside), and ii) to characterize Salmonella enterica serotypes abundance in informal markets in Cambodia. A total of 310 samples were screened for Salmonella enterica prevalence following the U.S. Department of Agriculture guidelines and confirmed by PCR. Whole Genome Sequencing was performed and the serotype for each isolate was determined in-silico using SeqSero 1.0 on draft genomes. A total of 78 samples were confirmed positive for Salmonella enterica . During the dry season, Salmonella enterica was more prevalent on FCS compared to NFCS (estimated probability of detection [confidence interval]: 0.41 [0.25,0.59] and 0.17 [0.08, 0.32], respectively; P=0.002), though no differences were apparent during the rainy season. Further, there was no evidence of any differences in Salmonella enterica prevalence based on location within the market (P=0.61). Sixteen Salmonella enterica serotypes were detected across multiple surfaces. The most common serotypes were Rissen (n=18), Hvittingfoss (n=11), Corvallis (n=10), Krefeld (n=8), Weltevreden (n=6), and Altona (n=6). The availability of accurate data on the prevalence of Salmonella enterica in informal markets is crucial for the development of effective surveillance and implementation of suitable intervention strategies at the domestic level, thus preventing future foodborne illness.

Genotypic and Phenotypic Characterization of Antimicrobial Resistance Profiles in Non-typhoidal Salmonella enterica Strains Isolated From Cambodian Informal Markets

“…A total of 81 S. enterica strains were used in this study. The strains were isolated in 2018 (June) and 2019 (January) from environmental samples collected from two informal markets in the province of Battambang, Cambodia ( Schwan et al, 2020a ). The strains were stored until further analysis at −80° ± 2.0°C in cryobeads (Key Scientific Products Inc., Stamford, TX-United States), following manufacturer protocol.…”

“…These factors often promote cross-contamination among food products, food contact surfaces and food handlers, favoring the spread of pathogens. The prevalence of S. enterica in the Cambodian informal market system has been previously determined, further indicating that cross-contamination is likely occurring ( Schwan et al, 2020a ). The ubiquity of S. enterica and its ability to cause human infections demonstrates that research needs to be conducted to better understand persistence and genotypic characteristics (e.g., virulence factors, antimicrobial resistance) in the serotypes present in these markets.…”

A case report of Salmonella enterica serovar Corvallis from environmental isolates from Cambodia and clinical isolates in the UK

“…Corvallis has been isolated from food products and environments (food contact and non-food contact surfaces) in Southeast Asia, the USA, Brazil, North Africa and Europe [3,17,32]. Reports of highly antibiotic-resistant isolates of S. Corvallis have raised concerns within public health authorities around the world [33][34][35].…”

“…In January 2019, a group of researchers from Kansas State University travelled to Cambodia to investigate the prevalence of Salmonella on environmental surfaces in informal markets [17]. Salmonella was isolated from environmental samples and shipped to the USA for WGS analysis and characterization [18].…”

“…In Cambodia, studies revealed the presence of S. Corvallis in poultry [4], pork [6] and environmental [17] samples from retail and informal markets. The informal markets are characterized by open-air environments that lack basic food safety infrastructure, hygiene, sanitation or oversight [36].…”