Salmonella transfer potential between tomatoes and cartons used for distribution

Corrugated fiberboard boxes (cartons) can be reused during fresh market tomato packing and repacking. The fate of Salmonella on the new, used, and dirty tomato packaging cartons, and Salmonella transfer between tomatoes and new, used, and dirty packaging cartons was assessed. Mature green tomatoes or blank cartons were spot inoculated with cocktail of rifampicin-resistant Salmonella strains before touching cartons/tomatoes at 0, 1, or 24 h postinoculation. Tomatoes were placed on new, used, and dirty carton squares (5 by 5 cm) for 0, 1, and 7 days of contact at 12°C and 25°C with a relative humidity value of 85%. Transfer coefficients (TCs) were calculated for all conditions. Salmonella populations decreased following inoculation by 2–3 log units during 24 h drying regardless of storage temperature; the presence of debris enhanced survival at 12°C. In general, the highest transfer rates occurred with wet inoculum. The highest Salmonella transfer was calculated for wet inoculated tomatoes with 7 days of contact time at 25°C (TC = 14.7). Increasing contact time decreased TCs for new cartons, but increased TCs for used and dirty cartons. Regardless of carton condition or storage temperature, a greater population of Salmonella was transferred from tomatoes to cartons than from cartons to tomatoes. Salmonella transfer between tomatoes and cartons is highly dependent on moisture, with increased levels of moisture increasing transfer, highlighting the importance of harvesting and packing dry tomatoes

Microbial quality of agricultural water in Central Florida

<div><p>The microbial quality of water that comes into the edible portion of produce is believed to directly relate to the safety of produce, and metrics describing indicator organisms are commonly used to ensure safety. The US FDA Produce Safety Rule (PSR) sets very specific microbiological water quality metrics for agricultural water that contacts the harvestable portion of produce. Validation of these metrics for agricultural water is essential for produce safety. Water samples (500 mL) from six agricultural ponds were collected during the 2012/2013 and 2013/2014 growing seasons (46 and 44 samples respectively, 540 from all ponds). Microbial indicator populations (total coliforms, generic <i>Escherichia coli</i>, and enterococci) were enumerated, environmental variables (temperature, pH, conductivity, redox potential, and turbidity) measured, and pathogen presence evaluated by PCR. <i>Salmonella</i> isolates were serotyped and analyzed by pulsed-field gel electrophoresis. Following rain events, coliforms increased up to 4.2 log MPN/100 mL. Populations of coliforms and enterococci ranged from 2 to 8 and 1 to 5 log MPN/100 mL, respectively. Microbial indicators did not correlate with environmental variables, except pH (<i>P</i><0.0001). The <i>invA</i> gene (<i>Salmonella</i>) was detected in 26/540 (4.8%) samples, in all ponds and growing seasons, and 14 serotypes detected. Six STEC genes were detected in samples: <i>hly</i> (83.3%), <i>fliC</i> (51.8%), <i>eaeA</i> (17.4%), <i>rfbE</i> (17.4%), <i>stx-</i>I (32.6%), <i>stx-</i>II (9.4%). While all ponds met the PSR requirements, at least one virulence gene from <i>Salmonella</i> (<i>invA-</i>4.8%) or STEC (<i>stx-</i>I-32.6%, <i>stx-</i>II-9.4%) was detected in each pond. Water quality for tested agricultural ponds, below recommended standards, did not guarantee the absence of pathogens. Investigating the relationships among physicochemical attributes, environmental factors, indicator microorganisms, and pathogen presence allows researchers to have a greater understanding of contamination risks from agricultural surface waters in the field.</p></div

Precipitation and microbial indicator correlations for all ponds.

<p>Precipitation and microbial indicator correlations for all ponds.</p

Calculated MWQP values for all ponds for three consecutive growing seasons (MPN/100 mL).

<p>Calculated MWQP values for all ponds for three consecutive growing seasons (MPN/100 mL).</p

Fate and Growth Kinetics of Salmonella and Listeria monocytogenes on Mangoes During Storage

Imported mangoes have been linked to outbreaks of salmonellosis in the USA. The purpose of this research was to evaluate the persistence and growth kinetics of Salmonella and Listeria monocytogenes on the intact surface of whole ‘Ataulfo’, ‘Kent’, and ‘Tommy Atkins’ mangoes stored at three different temperatures. L. monocytogenes was also evaluated on fresh-cut ‘Tommy Atkins’ mangoes stored at 4, 12, 20 ± 2°C. Whole mangoes were spot inoculated with rifampicin-resistant pathogen cocktails (6 log CFU/mango) onto the midsection of whole fruit (n = 6). Fruit was stored at 12, 20, or 30 ± 2°C and sampled for up to 28 days. The specific growth rates derived from DMFit models as a function of time were used to develop secondary models. On ‘Kent’ mangoes, Salmonella had a population increase from 0.3 to 1.1 log CFU/mango with a linear growth rate of ∼0.004, 0.01, and 0.06 log CFU/mango/h at 12, 20, and 30°C, respectively. At 20 and 30°C, Salmonella growth rates were significantly higher than 12°C (P < 0.05). No clear Salmonella growth trend was observed; populations decreased up to 1.6 log CFU/mango on ‘Tommy Atkins’ and ‘Ataulfo’ at 12°C. Populations of L. monocytogenes on whole and fresh-cut mangoes declined regardless of temperature and storage period. Food safety during storage should be the top priority for fresh-cut tropical fruit processors

Pearson product moment correlation coefficients (r) with <i>P</i>-values determined between each of the physical, chemical, and biological water attributes for all ponds combined.

<p>Pearson product moment correlation coefficients (r) with <i>P</i>-values determined between each of the physical, chemical, and biological water attributes for all ponds combined.</p

Most Probable Number of Total coliform (♦), Generic <i>E</i>. <i>coli</i> (■), and enterococci (▲) (Log MPN/100 mL) from six agricultural ponds (Pond 4: D, Pond 5: E, Pond 6: F) with daily rainfall (mm/Day) in Central Florida.

<p><i>invA</i> positive sampling days were shown with “*”.</p

Physical conditions of the ponds when sampling started in 2012.

<p>Physical conditions of the ponds when sampling started in 2012.</p