Cross-Sectional Survey of Indicator and Pathogenic Bacteria on Vegetables Sold from Asian Vendors at Farmers’ Markets in Northern California

Abstract

A cross-sectional survey was conducted during summer 2013 to determine the occurrence of Escherichia coli, fecal coliforms (FCs), E. coli O157:H7, and Salmonella on raw vegetable commodities common to Asian cuisine from 21 vendors or farmers at six farmers' markets in northern California. Based on 242 samples from six commodities (basil, yardlong beans, bitter squash, okra, squash stems and leaves, cilantro), 100% of samples had detectable FCs and 20% had detectable E. coli. The mean concentrations were 0.67 log CFU/g and 1.26 log CFU per bundle for E. coli and 4.00 log CFU/g and 6.26 log CFU per bundle for FCs. Vegetables irrigated with ground versus surface water contained lower concentrations of FCs, but this difference was not observed for E. coli. Yardlong beans, bitter squash, and okra had lower levels of FCs compared with basil, cilantro, and squash stems and leaves. Sixteen (6.6%) samples had detectable levels of Salmonella serovars (Newport, Enteritidis, Agona, and Worthington), with the majority of positives found in cilantro and squash stems and leaves. There was a twofold higher probability of Salmonella contamination in samples from growers or vendors who stated that they used organic farming practices compared with samples from those using conventional farming practices. Lastly, the concentrations of FC and E. coli bacteria were significantly associated with Salmonella contamination: for each additional 100 CFU/g or bundle, the probability of Salmonella contamination increased by ∼15 and ∼30%, respectively. None of the samples had detectable E. coli O157:H7.

Prevalence and antimicrobial resistance of foodborne pathogens in select fresh produce procured from farmers' markets in Central Virginia

“…Because the presence of E. coli in fruits indicates possible fecal contamination during harvesting and/or handling, these findings should be taken seriously given that pathogenic E. coli O157:H7 often can come from the same contamination sources (Aslam et al, 2003; Fegan, Higgs, Vanderlinde, & Desmarchelier, 2003). Regardless of plant part classifications, the overall prevalence (9.4%) of E. coli obtained in our study was considerably lower than a study conducted by Pan et al (2015), which detected E. coli in 20% of 242 commodities including basil, beans, squash, okra, and cilantro obtained from farmers' markets in Northern California. Additionally, a recent survey (Scheinberg et al, 2017) in Pennsylvania, where a total of 152 samples of leafy vegetables including kale, lettuce and spinach obtained from farmers' markets were analyzed, detected the prevalence of E. coli in 25% of samples.…”

“…A prevalence study on 261 leafy green commodities obtained from the central coast of California also found no detectable Salmonella (Gorski et al, 2011). In contrast, a study conducted by Pan et al (2015) reported the presence of Salmonella in 6.6% of 242 fresh produce commodities. In another related study, Levy et al (2015) reported that prevalence of Salmonella was detected in 0.8% of 133 fresh herb samples obtained from 13 farmers' markets in Los Angeles, CA and Seattle, WA.…”

Modelling of Indicator Escherichia coli Contamination in Sentinel Oysters and Estuarine Water

“…Subsequently, mixed-effects negative binomial regression models were performed to predict the concentrations of E. coli in Model A of oyster and Model C of estuarine water. The negative binomial regression model is suitable for overly dispersed count data, and this method has been widely used in microbiological studies, such as pre-harvest contamination of indicator and pathogenic bacteria in mixed produce, and the impact of farm management and environmental factors on the level of indicator bacteria in spinach [34,35,36]. Furthermore, more advanced studies on diversity of microbial ecological interaction networks on metagenomic data and microbiome count data have also used negative binomial regression to generate proper statistical models [37,38,39].…”

Cross-Contamination on Atypical Surfaces and Venues in Food Service Environments

“…Farmers markets contain a variety of goods, both raw and RTE, which regularly change with the seasons (69,98). Many such goods sold at farmers markets, like leafy greens, vegetables, and fruits, have been consistently found to be contaminated with pathogens like L. monocytogenes, pathogenic E. coli, and Salmonella spp.…”

“…Many such goods sold at farmers markets, like leafy greens, vegetables, and fruits, have been consistently found to be contaminated with pathogens like L. monocytogenes, pathogenic E. coli, and Salmonella spp. (69,98). These goods must be stored and displayed in containers or on tables provided by the farmer or retailer.…”