Food safety concerns associated with products purchased at farmers' markets have arisen, highlighting the growing need for farmers' market consumer and producer awareness of potential public health issues. The focus of this quantitative research study was to assess the prevalence and antimicrobial resistance of foodborne pathogens in select value-added commodities (i.e., animal treats, soil amendments, herbs, honey, dressings, exotic foods, etc.) randomly procured from farmers' markets in Central Virginia. Between March and November 2017, collection of 194 samples originating from 40 individual farmers' market vendors selling at 11 different farmers' markets transpired. Detection of potentially harmful bacterial species within collected samples was as follows: 0.5% Campylobacter, 24.5% Escherichia coli, 16.7% Listeria, and 1.0% Salmonella. Bacterial isolates (n = 155) of Campylobacter, E. coli, Listeria, and Salmonella were tested for their susceptibility to 12 antimicrobials. Tetracycline and ampicillin resistance showed the highest frequency among E. coli (approximately 30%) isolates. Nalidixic acid resistance was the highest in Listeria isolates (79.4%). Approximately 17% of E. coli isolates and more than 50% of each Campylobacter, Listeria, and Salmonella isolates exhibited multidrug resistance (MDR). No E. coli isolates had matching pulsed-field gel electrophoresis profiles demonstrating that the isolates had a high degree of genomic diversity and farm specificity. This study demonstrated an emerging public health threat of the presence of MDR arising from farmers' market-acquired value-added commodities. The importance of this research study highlights the value of implementing good agricultural and handling practices from farm (producer vendors) to table (consumers) to avert potential foodborne illness occurrence. Future research to determine potential reasons and supply chain interventions for the observed prevalence of MDR bacterial isolates from farmers' market value-added products is paramount.Disclaimer: This study simply indicates the occurrence and multidrug resistance (MDR) of foodborne pathogens on various and randomly selected value-added commodities available at farmers' markets in Virginia. Due to the limited availability of same commodities at different vendors among farmers' markets, each commodity acquired in duplicate may not be representative of all value-added commodities in the study area. However, the findings are noteworthy to understand the prevalence and MDR of foodborne pathogens on those commodities available at farmers' markets in broad spectrum. The authors would like to declare that this study was carried out, mainly for academic research purpose without any conflict of interest. Furthermore, mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by Virginia State University.

Improper food processing is one of the major causes of foodborne illness. Accurate prediction of the thermal destruction rate of foodborne pathogens is therefore vital to ensure proper processing and food safety. When bacteria are subjected to pH and thermal stresses during growth, sublethal stresses can occur that may lead to differences in their subsequent tolerance to thermal treatment. As a preliminary study to test this concept, the current study evaluated the effect of prior pH and thermal stresses on thermal tolerance of Salmonella and Staphylococcus using a tryptic soy broth supplemented with yeast extract. Bacteria incubated at three pH values (6.0, 7.4, and 9.0) and four temperatures (15, 25, 35, and 45°C) for 24 hr were subjected to thermal treatments at 55, 60, and 65°C. At the end of each treatment time, bacterial suspensions were surface‐plated on standard method agar for quantification of bacterial survival and further calculation of the thermal death decimal reduction time ( D ‐value) and thermal destruction temperature ( z ‐value). The effect of pH stress alone during the incubation on the thermal tolerance of both bacteria was generally insignificant. An increasing pattern of D ‐value was observed with the increment of thermal stress (incubation temperature). The bacteria incubated at 35°C required the highest z ‐value to reduce the 90% in D ‐values . Staphylococcus mostly displayed higher tolerance to thermal treatment than Salmonella . Although further research is needed to validate the current findings on food matrices, findings in this study clearly affirm that adaptation of bacteria to certain stresses may reduce the effectiveness of preservation procedures applied during later stage of food processing and storage.

As farmers' markets have increased in size, scope, and complexity, so have potential food‐safety challenges and implications. Most products sold at farmers' markets may receive minimal to no treatment of decontamination which could increase their potential microbial risks. The aim of this study was to assess the prevalence and antimicrobial resistance (AMR) of foodborne pathogens in select fresh produce procured from farmers' markets in Central Virginia. A total of 138 samples produced by 15 farms and sold at 9 registered farmers' markets were obtained between March and November 2017. Campylobacter, Escherichia coli, and Listeria were, respectively, detected in 8.7, 9.4, and 8.0% of the samples. A total of 46 bacterial isolates consisted of Campylobacter, E. coli, and Listeria were tested for their susceptibility to 12 antimicrobials. Ampicillin resistance showed the highest frequency among Campylobacter (100%) and E. coli (47.8%) isolates while nalidixic acid resistance was the highest in Listeria isolates (72.7%). At least 17% of each Campylobacter, E. coli, and Listeria isolates exhibited multidrug resistance (MDR). No isolates had matching pulsed‐field gel electrophoresis (PFGE) profiles demonstrating that the E. coli isolates had a high degree of genomic diversity. This study demonstrated a potential health hazard arising from farmers' market‐acquired fresh produce and emphasizes the importance of good agricultural and handling practices to prevent foodborne illness and spread of multidrug antibiotic resistance. Continued research is needed to determine and intervene the cause(s) of the observed prevalence and to support the healthy development of food products sold at farmers' markets.

Accurate prediction of the thermal destruction rate of foodborne pathogens is important for food processors to ensure proper food safety. When bacteria are subjected to thermal stress during storage, sublethal stresses and/or thermal acclimation may lead to differences in their subsequent tolerance to thermal treatment. The aim of the current study was to evaluate the thermal tolerance of Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica, and Staphylococcus aureus that are incubated during overnight growth in tryptic soy broth at four temperatures (15, 25, 35, and 45°C). Following incubation, the bacteria were subjected to thermal treatments at 55, 60, and 65°C. At the end of each treatment time, bacterial survival was quantified and further calculated for the thermal death decimal reduction time (D‐value) and thermal destruction temperature (z‐value) using a linear model for thermal treatment time (min) vs. microbial population (Log CFU/ml) and thermal treatment temperature (°C) vs. D‐value, respectively, for each bacterium. Among the four bacterial species, E. coli generally had longer D‐values and lower z‐values than did other bacteria. Increasing patterns of D‐ and z‐values in Listeria were obtained with the increment of incubation temperatures from 15 to 45°C. The z‐values of Staphylococcus (6.19°C), Salmonella (6.73°C), Listeria (7.10°C), and Listeria (7.26°C) were the highest at 15, 25, 35, and 45°C, respectively. Although further research is needed to validate the findings on food matrix, findings in this study clearly affirm that adaptation of bacteria to certain stresses may reduce the effectiveness of preservation hurdles applied during later stages of food processing and storage.

No abstract