Fresh produce outbreaks due to Shiga toxin-producing Escherichia coli (STEC) continue to occur in the United States (US). Manure-amended soils can pose a public health risk when used for growing raw agricultural commodities. Knowing the prevalence and concentration of STEC in untreated biological soil amendments of animal origin (BSAAO) is important to help guide the most appropriate pre-harvest interval(s) following application to limit risks from these soil amendments. Bovine manure samples were collected from 12 farms in Florida, including samples from piles, lagoons, barns, and screened solids. Two methods were used to detect stx1 / 2 and rfbE genes in samples. A prevalence rate of 9% for stx1 and/or stx2 and 19% for rfbE was observed from the 518 bovine manure samples evaluated. A most probable number (MPN) assay was performed on stx + samples when applicable. The geometric mean for stx+ samples (n = 20) was 3.37 MPN g -1 (0.53 log MPN g -1 ) with a maximum value of 6,800 MPN g -1 (3.83 log MPN g -1 ). This research was part of a larger nationwide geographical study on the prevalence and concentration of STEC in bovine manure to help guide regulations on feasible pre-harvest intervals for the application of untreated BSAAO.

Ingesting foods contaminated with Bacillus cereus bacteria can lead to nausea, vomiting, abdominal cramps, and diarrhea. Though B. cereus is commonly found in many types of fresh and processed foods, proper cooking, handling, and storage can minimize the risk of contamination. This revised 6-page fact sheet explains how B. cereus is transmitted, what foods it is commonly associated with, the methods used to prevent contamination, and good practices for receiving, handling, processing, and storing food. Written by Keith R. Schneider, Renée Goodrich Schneider, Rachael Silverberg, Ploy Kurdmongkoltham, and Bruna Bertoldi, and published by the Department of Food Science and Human Nutrition, April 2017. FSHN15-06/FS269: Preventing Foodborne Illness: Bacillus cereus (ufl.edu)

This 7-page fact sheet is one in a series of fact sheets discussing common foodborne pathogens of interest to food handlers, processors, and retailers. It covers the characteristics of, and symptoms caused by, the bacterium E. coli (particularly the “big six” strains), and also details how to minimize the risk of spreading or contracting an E. coli infection. Written by Bruna Bertoldi, Susanna Richardson, Renee Goodrich-Schneider, Ploy Kurdmongkoltham, and Keith R. Schneider and published by the UF/IFAS Department of Food Science and Human Nutrition, January 2018. http://edis.ifas.ufl.edu/fs233

Florida peaches (Prunus persica) typically are picked and placed in a cold room on the day of harvest, then packed and shipped the next day. This room cooling (RC) is slow, requiring ≈24 hours or more for the fruit to reach optimal temperature (6 to 7 °C). There is currently limited research on the effect of cooling practices on microbial quality of peaches, yet this study is essential for decision making in areas such as upgrading packing house facilities and the implementation of improved handling procedures. This research compared the efficacies of postharvest cooling by RC, forced-air cooling (FAC), and hydrocooling with sanitizer (HS) treatment of peaches to reduce their surface microbial population and to determine the effect on shelf life and microbial quality. Three trials for RC and two trials each for FAC and HS were performed. Following cooling, fruit were stored at 1 °C. The average aerobic plate count (APC) from field samples was 5.29 log cfu/peach, which remained unchanged after RC or FAC but was reduced significantly (P < 0.05) to 4.63 log cfu/peach after HS. The average yeast and mold counts (Y&M) from field samples (6.21 log cfu/peach) were reduced highly significantly (P < 0.001) to 4.05 log cfu/peach after HS. Hydrocooling significantly (P < 0.05) reduced the APC and Y&M counts from the peaches and showed promise in maintaining the microbiological quality of the fruit throughout storage. However, at the end of the 21-day storage period, there was no significant difference in APC or Y&M counts from peaches, irrespective of the cooling methods. Peaches that went through the hydrocooling process and were subsequently packed showed an increase (P < 0.05) in both APC and Y&M counts, while fruit that were not hydrocooled showed no such increase. Information obtained will be used to recommend the best temperature management practices for maintaining the postharvest quality of peaches. A detailed cost-benefit analysis of different cooling methods and the time interval between harvest and shipment are both necessary for a more conclusive recommendation.

Clostridium botulinum is the bacterium that causes botulism. Clostridium botulinum is a Gram-positive, slightly curved, motile, anaerobic rod-shaped bacterium that produces heat-resistant endospores. These endospores, which are very resistant to a number of environmental stresses such as heat and high acid, can become activated in anaerobic environments, low acidity (pH > 4.6), high moisture content, and in temperatures ranging from 40ºF to 250ºF (4ºC to 121ºC) (Sobel et al. 2004). In hostile environmental conditions, the heat-resistant spores enable the bacteria to survive for extended periods of time in a dormant state until conditions become more favorable.

Botulism is caused by the nerve toxins produced by the bacterium Clostridium botulinum, often resulting in a serious paralytic condition that can lead to death. This document is FSHN04-06, one of a series of the Food Science and Human Nutrition Department discussing common foodborne pathogens of interest to food handlers, processors, and retailers; Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Date Published: November 2004. FSHN0406/FS104: Preventing Foodborne Illness: Clostridium botulinum (ufl.edu)

Monitoring and maintenance of water quality in dump tanks or flume systems is crucial to prevent pathogen cross-contamination during postharvest washing of tomatoes, but there is limited information on how organic matter influences sanitizer efficacy in the water. The main objective of this study was to monitor water quality in flume tanks and evaluate the efficacy of postharvest washing of tomatoes in commercial packinghouses. Flume tank water samples (n=3) were collected on an hourly basis from three packinghouses in Florida and analyzed for pH, total dissolved solids (TDS), free chlorine, chemical oxygen demand (COD), oxidation-reduction potential (ORP), and turbidity. Additionally, three flume water samples were collected and tested for total aerobic plate count (APC), total coliforms (TC), and generic E. coli (EC). Fresh tomatoes (n=3), both before and after washing, were collected and analyzed for the same bacterial counts. Turbidity, COD, and TDS levels in flume water increased over time in all packinghouses. Correlations observed include COD and turbidity (r = 0.631), turbidity and TDS (r = 0.810), and ORP and chlorine (r = 0.660). APC for water samples had an average range of 0.0 to 4.7 log CFU/mL and TC average range of 0.0 to 4.7 log CFU/mL. All water samples were negative for generic E. coli . The average APC for pre-and post-flume tomatoes from the three packinghouses was 6.0 log CFU/tomato and ranged from 2.2 to 7.4 log CFU/tomato. The average TC count was &lt;1.5 and 7.0 log CFU/tomato for pre-and post-wash tomatoes, respectively. There was no significant effect ( P &gt;0.05) of postharvest washing on the microbiological qualities of tomatoes. Water quality in flume tanks deteriorated over time in all packinghouses during a typical operational day of 4-8 h.

The process of washing tomatoes in dump (flume) tanks has been identified as a potential source of cross-contamination. This study's objective was to assess the potential for Salmonella enterica cross-contamination at various inoculation levels at the presence of 0 and 25 mg/L free chlorine (HOCl) and organic matter.  Uninoculated tomatoes were introduced into a laboratory-based model flume containing tomatoes inoculated with a cocktail of five rifampicin-resistant Salmonella enterica serovars at 104, 106, or 108 CFU/tomato in water containing 0 or 25 mg/L HOCl and 0 or 300 mg/L chemical oxygen demand (COD). Uninoculated tomatoes were removed from the water at after 5, 30, 60, 120 s and were placed in bags containing tryptic soy broth supplemented with rifampicin and 0.1% sodium thiosulfate. Following incubation, enrichments were plated on tryptic soy agar supplemented with rifampicin and xylose lysine deoxycholate agar to determine the presence of Salmonella. HOCl and pH were measured before and after each trial. The HOCl in water containing 300 mg/L COD significantly (P≤0.05) declined by the end of each 120 s trial, most likely due to the increased demand for the oxidant. Higher inoculum levels and lower HOCl concentrations were (P≤0.05) significant factors that contributed to increased cross-contamination seen in this study. When HOCl levels were at 25 mg/L, no Salmonella was recovered on non-inoculated tomatoes under all conditions when inoculum levels were at 104 CFU/tomato. When the inoculum was increased to 106 and 108 CFU/tomato, cross-contamination was observed, independent of COD levels. The results from this study show that the currently required sanitizer level (e.g., 100 or 150 mg/L) for flume water may be higher than necessary and warrants re-evaluation.