Modulation of innate immunity in Nile tilapia (Oreochromis niloticus) by dietary supplementation of Bacillus subtilis endospores.

Dietary supplementation of probiotics is growing as a scientifically valid alternative to antibiotics for enhancement of overall animal health and productivity in aquaculture. Strains of Bacillus subtilis are regarded as attractive probiotic candidates to the fish farming industry; however, there is a limited number of studies focused on the use of specific strains probiotics in tilapia, and therefore complicating replication. The objective of this study was to examine the effect of the strains NZ86 (NRRL B-50136) and O14VRQ (NRRL B-67221) of B. subtilis on various parameters of the innate immunity in Nile tilapia (Oreochromis niloticus) in a 51-day feeding trial. Supplementation of tilapia with either strain resulted in significant increases (p < 0.05) in plasma lysozyme concentration of varying degrees throughout the trial. Meanwhile, alternative complement activity was significantly elevated (p < 0.05) only after feeding of the NZ86 strain after 14 and 51 days. Conversely, supplementation with O14VRQ resulted in a significant increase (p < 0.05) in the percent of neutrophils in the peripheral blood of tilapia by day 28. At the end of the trial, there was a trend towards increased phagocytic and respiratory burst activities observed in immune organ derived leukocytes. Feeding with either probiotic appeared to have an up-regulation on the gene expression of both pro-inflammatory cytokines in the intestine, yet only O14VRQ was significantly different than the control. Moreover, the occurrence of these results could be associated with supplementation of the probiotic strains, given that Bacillus bacteria were observed to populate the intestines of the dietary treatment groups. These results suggest the potential roles of these B. subtilis probiotic candidates to stimulate immune responses both locally and systemically in tilapia.

Survival of Tomato Outbreak Associated Salmonella Serotypes in Soil and Water and the Role of Biofilms in Abiotic Surface Attachment.

Salmonella serotypes linked to tomato-associated outbreaks were evaluated for survival in soil and water over a 40-day period. Salmonella enterica serotypes Anatum, Baildon, Braenderup, Montevideo, Newport, and Javiana were inoculated separately into sterile soil and water, followed by plating onto TSAYE and XLT4 at 10-day intervals. Biofilm production by Salmonella serotypes was measured on both quartz particles (soil surrogate) and glass coverslips, and was evaluated using a crystal violet dye assay. Salmonella populations in soil and water over 40 days indicated no significant differences between Salmonella serotypes tested (p > 0.05). Over a 40-day period, there was a 1.84 ± 0.22 log CFU/g and 1.56 ± 0.54 CFU/mL decrease in populations of Salmonella in soil and water, respectively. Enumeration indicated that Salmonella population fluctuated in water but decreased linearly in soil. All serotypes tested produced the "red dry and rough" morphotype on Congo Red agar. Biofilm produced by all the Salmonella serotypes tested was significantly different on quartz particles than on glass coverslips (p < 0.0001), indicating that material and surface characteristics could affect biofilm development. The ability of Salmonella serotypes to persist in soil or water and attach to abiotic surfaces through biofilm formation affirms that contact surfaces, soil, water, and sediment should be considered as possible sources of cross-contamination in the farm environment.

Cetylpyridinium chloride direct spray treatments reduce Salmonella on cantaloupe rough surfaces.

Cetylpyridinium chloride (CPC) solutions (0, 0.5, or 1.0%) were applied to cantaloupe ("Athena" and "Hale's Best Jumbo" cultivars) rind plugs, either before or after inoculation with a broth culture of Salmonella Michigan (109 CFU/mL) and held at 37°C for 1 or 24 hr. Rind plugs were diluted, shaken, and sonicated, and solutions were enumerated. Texture quality and color were evaluated over 14 days storage at 4°C after 0 and 1% CPC spray applications. A 0.5 or 1.0% (vol/vol) application of CPC after Salmonella reduced the pathogen levels between 2.34 log CFU/mL and 5.16 log CFU/mL in comparison to the control (p < .01). No differences were observed in the firmness and color of 1% CPC treated cantaloupes. Salmonella concentrations on cantaloupes, treated with 1.0% CPC, were lower after 1 hr storage as compared to 24 hr. And, Salmonella on "Athena" surfaces were more susceptible to CPC spray treatments than on "Hale's Best Jumbo." PRACTICAL APPLICATIONS: Cetylpyridinium chloride (CPC) is the active ingredient of some antiseptic oral mouth rinses, and has a broad antimicrobial spectrum with a rapid bactericidal effect on gram-positive pathogens. The spray application of CPC solutions to cantaloupe may reduce the level of Salmonella surface contamination during production from irrigation water and manure fertilizers and, during food processing by contaminated equipment and food handlers. Since the surfaces of cantaloupes are highly rough or irregular, bacteria can easily attach to these surfaces and become difficult to remove. Appropriate postharvest washing and sanitizing procedures are needed that can help control Salmonella and other pathogens on melons, especially on cantaloupes with nested surfaces. A direct surface spray application of CPC may be an alternative antimicrobial postharvest treatment to reduce pathogen contamination of cantaloupe melons, while providing an alternative to chlorine-based solutions.

Association of Campylobacter spp. levels between chicken grow-out environmental samples and processed carcasses.

Campylobacter spp. have been isolated from live poultry, production environments, processing facilities, and raw poultry products. Environmental sampling in a poultry grow-out house, combined with carcass rinse sampling from the same flock, may provide a relative relationship between pre- and postharvest Campylobacter contamination. Air samples, fecal/litter samples, and feed/drink line samples were collected from 4 commercial chicken grow-out houses in western Virginia between September 2011 and January 2012. Birds from each sampled house were the first flock slaughtered the following day and were then sampled by postchill carcass rinses. Campylobacter, from postenrichment samples, was detected in 27% (32/120) of house environmental samples and 37.5% (45/120) of carcass rinse samples. All environmental sample types from each house included at least one positive sample except the house 2 air samples. The sponge sample method was found to have a significantly higher (P < 0.05) proportion of Campylobacter-positive samples (45%) than the fecal/litter samples (20%) and air samples (15%) when sample types of all the houses were compared. The proportion positive for the fecal/litter samples postenrichment, for each flock, had the highest correlation (0.85) to the proportion of positive carcass rinse samples for each flock. Environmental samples from house 1 and associated carcass rinses accounted for the largest number of Campylobacter positives (29/60). The fewest number of Campylobacter positives, based on both house environmental (4/30) and carcass rinse samples (8/30), was detected from flock B. The results of this study suggest that environmental sampling in a poultry grow-out house, combined with carcass rinse sampling from the same flock, have the potential to provide an indication of Campylobacter contamination and transmission. Campylobacter qualitative levels from house and processing plant samples may enable the scheduled processing of flocks with lower pathogen incidence or concentrations, as a way to reduce postslaughter pathogen transmission.

Dose of UV light required to inactivate Listeria monocytogenes in distilled water, fresh brine, and spent brine.

The purpose of this research was to establish the dose of UV light (253.7 nm) needed to inactivate Listeria monocytogenes in distilled water, fresh brine (9% NaCl), spent brine, and diluted (5, 35, and 55%) spent brine, using uridine as a chemical actinometer. Strains N1-227 (isolated from hot dog batter), N3-031 (isolated from turkey franks), and R2-499 (isolated from meat) were mixed in equal proportions and suspended in each solution prepared so as to contain 10(-4) M uridine. Samples were irradiated in sterile quartz cells for 0, 5, 10, 15, 20, 25, or 30 min. Inactivation was evaluated by serially diluting samples in 0.1% peptone, by surface plating in duplicate onto modified Oxford agar and Trypticase soy agar with yeast extract, and by enrichment in brain heart infusion broth, followed by incubation at 37 degrees C for 24 to 48 h. For dose measurements, the absorbance (262 nm) was measured before and after irradiation. Differences were observed in population estimates depending on the solution (P < or = 0.05). Reductions were as follows from greatest to least: water > fresh brine > 5% spent brine > 35% spent brine > 55% spent brine > undiluted spent brine. UV light did not significantly reduce populations suspended in spent brine solutions. L. monocytogenes decreased to below the detection limit (1 log CFU/ml) at doses greater than 33.2 mJ/cm(2) in water and at doses greater than 10.3 mJ/cm(2) in fresh brine. Knowledge of UV dosing required to control L. monocytogenes in brines similar to those used for ready-to-eat meat processing will aid manufacturers in establishing appropriate food safety interventions for these products.

Effect of acid stress, antibiotic resistance, and heat shock on the resistance of Listeria monocytogenes to UV light when suspended in distilled water and fresh brine.

Exposure to sublethal processing treatments can stimulate bacterial stress responses. The purpose of this research was to determine whether adaptation to common food processing stresses encountered during the preparation of ready-to-eat foods affects the dose of UV light required to significantly reduce Listeria monocytogenes populations in sterile distilled water and a 9% NaCl solution, using uridine as a chemical actinometer. L. monocytogenes strains N1-227 (from hot dog batter), N3-031 (from turkey franks), and R2-499 (from ready-to-eat meat) were acid stressed for 3 h at 35 degrees C in Trypticase soy broth with yeast extract acidified to pH 5.0, heat shocked for 1 h at 48 degrees C in brain heart infusion broth (BHIB), and selected for sulfanilamide resistance (512 microg/ml). These strains were then mixed in equal proportions and suspended in water and 9% NaCl solution, each containing 10(-4) M uridine. Samples were exposed to UV light (253.7 nm) for 0, 5, 10, 15, 20, 25, or 30 min. Inactivation was evaluated by surface plating onto modified Oxford agar and Trypticase soy agar with yeast extract and by enrichment in BHIB followed by incubation at 37 degrees C for 24 h. The absorbance of each sample was measured before and after irradiation to calculate the dose of UV light. There were no significant differences between population estimates based on medium or suspension solution. There were no population differences between acid-stressed and antibiotic-resistant or unstressed and heat-shocked L. monocytogenes strains. However, acid-stressed and antibiotic-resistant strains were significantly more resistant to UV light than were unstressed and heat-shocked strains (P < or = 0.05).

Delmopinol hydrochloride reduces Salmonella on cantaloupe surfaces.

Since the surfaces of cantaloupes are highly rough or irregular, bacteria can easily attach and become difficult to remove. Appropriate postharvest washing and sanitizing procedures can help control Salmonella and other pathogens on cantaloupe or other melons during postharvest operations. Delmopinol hydrochloride (delmopinol) is a cationic surfactant that is effective for treating and preventing gingivitis and periodontitis. The application of delmopinol to two cantaloupe cultivars was evaluated for reducing the level of inoculated Salmonella. Athena and Hale's Best Jumbo (HBJ) cantaloupe rind plugs (2.5 cm. dia.) were inoculated with nalidixic acid-resistant Salmonella Michigan (approx. 1.0 × 109 CFU/ml). After 15 min, rind plugs were sprayed with 10 ml of a delmopinol spray solution (0% or 1.0% vol/vol) and held at 35°C for 1 hr or 24 hr. Rind plugs were diluted with Butterfield's phosphate buffer, shaken and sonicated, and solutions were enumerated on 50 ppm nalidixic acid-tryptic soy agar. The texture quality and color of additional cantaloupes were evaluated, after 1% delmopinol spray treatment, over 14-day storage at 4°C. A 1.0% application of delmopinol after 1 hr reduced Salmonella concentration by ~3.1 log CFU/ml for both "HBJ" skin rind plugs and "Athena" stem scar rind plugs in comparison to the control (p < .05). No differences were observed in the texture and color (L*, a*, b* values) of 1% delmopinol-treated cantaloupes as compared to control. Storage of cantaloupes treated with 1.0% delmopinol solution for 1 hr had a greater effect on reducing concentration of Salmonella compared to 24-hr treatment. A surface spray application of 1% delmopinol on cantaloupes could be an alternative antimicrobial postharvest treatment that could make surface bacteria more susceptible to sanitizers or physical removal.

Incidence of Listeria spp. in Ready-to-Eat Food Processing Plant Environments Regulated by the U.S. Food Safety and Inspection Service and the U.S. Food and Drug Administration.

A multiyear survey of 31 ready-to-eat (RTE) food processing plants in the United States was conducted to determine the incidence of Listeria spp. in various RTE production environments. Samples were collected from 22 RTE plants regulated by the U.S. Department of Agriculture's Food Safety and Inspection Service (FSIS) and from 9 RTE food plants regulated by the U.S. Department of Health and Human Services' Food and Drug Administration (FDA). Only nonfood contact surfaces in the RTE manufacturing areas with exposed RTE product were sampled. Each sample was individually analyzed for the presence of Listeria spp. by using a PCR-based rapid assay. In total, 4,829 samples were collected from various locations, including freezers, equipment framework, floors, walls, wall-floor junctures, drains, floor mats, doors, and cleaning tools. Nine (29%) of the facilities had zero samples positive for Listeria spp. in the production environment, whereas 22 (71%) had one or more samples positive for Listeria spp. The total incidence of Listeria spp. in all RTE food plants was 4.5%. The positive rate in plants regulated by the FSIS ranged from 0 to 9.7%, whereas the positive rate in plants regulated by the FDA ranged from 1.2 to 36%.

Effects of modified atmosphere packaging on toxin production by Clostridium botulinum in raw aquacultured summer flounder fillets (Paralichthys dentatus).

Packaging fishery products under vacuum atmosphere packaging (VAC) and modified atmosphere packaging (MAP) conditions can significantly extend the shelf life of raw, refrigerated fish products. There is considerable commercial interest in marketing VAC and MAP refrigerated (never frozen) raw fish fillets. The objective of this study was to determine if Clostridium botulinum toxin development precedes microbiological spoilage in raw, refrigerated flounder fillets. Aquacultured flounder (Paralichthys dentatus) individual fish fillets either were packed with a film having an oxygen transmission rate (OTR) of 3000 cm3 m(-2) 24 h(-1) at 22.8 degrees C or were vacuum packaged or packaged under 100% CO2 with a film having an OTR of 7.8 cm3 m(-2) 24 h(-1) at 21.1 degrees C and were stored at 4 and 10 degrees C. Samples were analyzed by aerobic plate count (APC) for spoilage and qualitatively for botulinum toxin with a mouse bioassay. The results demonstrate that flounder fillets (4 degrees C) packaged with a film having an OTR of 3,000 were microbiologically spoiled (APC, > 10(7) CFU/g) on day 15, but there was no toxin formation, even after 35 days of storage. However, at 10 degrees C, toxin production occurred (day 8), but it was after microbial spoilage and absolute sensory rejection (day 5). Vacuum-packaged fillets and 100% CO2 fillets (4 degrees C) packaged with a film having an OTR of 7.8 were toxic on days 20 and 25, respectively, with microbial spoilage (APC, >10(7) CFU/g) not occurring during the tested storage period (i.e., >35 days). At 10 degrees C, in vacuum-packaged flounder, toxin formation coincided with microbiological spoilage (days 8 to 9). In the 100% CO2-packaged fillets, toxin formation occurred on day 9, with microbial spoilage occurring on day 15. This study indicates that films with an OTR of 3,000 can be used for refrigerated fish fillets and still maintain the safety of the product.

Evaluation of quantitative recovery methods for Listeria monocytogenes applied to stainless steel.

The ability of Listeria monocytogenes to attach to various food contact surfaces, such as stainless steel, polypropylene, and rubber compounds, is well documented. The retention of these or other pathogenic bacteria on food contact surfaces increases the risk of transmission to food products. The objective of this study was to compare several methods for quantitative recovery of Listeria monocytogenes from stainless steel surfaces. A cocktail of 4 serotypes of Listeria monocytogenes mixed in equivalent concentrations was inoculated onto type 304 stainless steel coupons in a 2 x 2 cm area. After 1 h exposure, coupons were sampled by one of the following methods: (1) swabbing with a premoistened Dacron swab; (2) rinsing with phosphate-buffered saline; (3) direct contact onto tryptic soy agar containing 0.6% yeast extract (TSA + YE) plates for 10 s; (4) sonication in an ultrasonic water bath (40 kHz); (5) contact with the bristles of a sonicating brush head for 1 min; and (6) indirect contact (2-4 mm distance) with a sonicating brush head for 1 min. The 3 sonication methods yielded higher recovery than the other 3 methods (P < 0.05). Brushing the coupons with the sonicating brush head (contact or noncontact) yielded a recovery level of about 60%. The lowest cell recovery (about 20%) was observed with the swab and direct agar contact methods. After a 12 h exposure, recoveries ranged from 17.4 (brush contact method) to 2% (swab method).

Quantitative recovery of Listeria monocytogenes and select salmonella serotypes from environmental sample media.

Environmental sampling has become increasingly important in the food industry for monitoring the presence of specific pathogens such as Listeria monocytogenes and Salmonella enterica. Several microbiological media are available for storage and transport of environmental samples from the processing plant to the test laboratory. In this study, we quantified the survival of L. monocytogenes, S. Typhimurium, S. Enteritidis, and S. Typhi in environmental sampling media over several time and temperature combinations to determine optimum conditions for transport and storage. A cocktail of L. monocytogenes strains and Salmonella serotypes was separately added to tubes of Dey-Engley (D/E) Neutralizing Broth, Copan SRK solution, and Neutralizing Buffer and incubated at either -4, 4, 10, or 15 degree C. Counts were made of the bacterial load after 0, 12, 24, and 48 h. Neutralizing Buffer and Copan SRK solution were best at maintaining bacterial concentrations at all temperatures. D/E Neutralizing Broth, at 10 and 15 degrees C, allowed significant bacterial growth. This study helped validate the use of these 3 media for environmental sample transport and storage at cold holding temperatures and demonstrated that, at elevated temperatures (>4 degrees C), it is preferable to use Neutralizing Buffer or Copan SRK solution for quantifying microbial recovery.

Airborne soil particulates as vehicles for Salmonella contamination of tomatoes.

The presence of dust is ubiquitous in the produce growing environment and its deposition on edible crops could occur. The potential of wind-distributed soil particulate to serve as a vehicle for S. Newport transfer to tomato blossoms and consequently, to fruits, was explored. Blossoms were challenged with previously autoclaved soil containing S. Newport (9.39log CFU/g) by brushing and airborne transfer. One hundred percent of blossoms brushed with S. Newport-contaminated soil tested positive for presence of the pathogen one week after contact (P<0.0001). Compressed air was used to simulate wind currents and direct soil particulates towards blossoms. Airborne soil particulates resulted in contamination of 29% of the blossoms with S. Newport one week after contact. Biophotonic imaging of blossoms post-contact with bioluminescent S. Newport-contaminated airborne soil particulates revealed transfer of the pathogen on petal, stamen and pedicel structures. Both fruits and calyxes that developed from blossoms contaminated with airborne soil particulates were positive for presence of S. Newport in both fruit (66.6%) and calyx (77.7%). Presence of S. Newport in surface-sterilized fruit and calyx tissue tested indicated internalization of the pathogen. These results show that airborne soil particulates could serve as a vehicle for Salmonella. Hence, Salmonella contaminated dust and soil particulate dispersion could contribute to pathogen contamination of fruit, indicating an omnipresent yet relatively unexplored contamination route.

Shelf Life Determination of Fresh Blueberries (Vaccinium corymbosum) Stored under Controlled Atmosphere and Ozone.

Fresh blueberries are commonly stored and transported by refrigeration in controlled atmospheres to protect shelf life for long periods of storage. Ozone is an antimicrobial gas that can extend shelf life and protect fruit from microbial contamination. Shelf life of fresh highbush blueberries was determined over 10-day storage in isolated cabinets at 4°C or 12°C under different atmosphere conditions, including air (control); 5% O2 : 15% CO2 : 80% N2 (controlled atmosphere storage (CAS)); and ozone gas (O3) 4 ppm at 4°C or 2.5 ppm at 12°C, at high relative humidity (90-95%). Samples were evaluated for yeast and molds growth, weight loss, and firmness. CAS and O3 did not delay or inhibit yeast and molds growth in blueberries after 10 days at both temperatures. Fruit stored at 4°C showed lower weight loss values compared with 12°C. Blueberries stored under O3 atmosphere showed reduced weight loss at 12°C by day 10 and loss of firmness when compared to the other treatments. Low concentrations of ozone gas together with proper refrigeration temperature can help protect fresh blueberries quality during storage.

Inhibition of pathogens on fresh produce by ultraviolet energy.

Ultraviolet energy at a wavelength of 253.7 nm (UVC) was investigated for its bactericidal effects on the surface of Red Delicious apples, leaf lettuce and tomatoes inoculated with cultures of Salmonella spp. or Escherichia coli O157:H7. Inoculated samples were subjected to different doses ranging from 1.5 to 24 mW/cm(2) of UVC and enumerated on tryptic soy agar plus 0.05 g/l nalidixic acid to determine effective log reductions of microbial populations. UVC applied to apples inoculated with E. coli O157:H7 resulted in the highest log reduction of approximately 3.3 logs at 24 mW/cm(2). Lower log reductions were seen on tomatoes inoculated with Salmonella spp. (2.19 logs) and green leaf lettuce inoculated with both Salmonella spp. and E. coli O157:H7 (2.65 and 2.79, respectively). No significant statistical difference (p>0.05) was seen in the ability of UVC to inactivate a higher population of either Salmonella spp. or E. coli O157:H7 on the surface of green leaf lettuce. No significant difference was seen among the use of different doses applied to the surface of fresh produce for reduction of E. coli O157:H7 or Salmonella spp. (p>0.05). The use of UVC may prove to be beneficial in protecting the safety of fruits and vegetables in conjunction with Good Agricultural Practices and Good Manufacturing Practices.

Response of Salmonella and Escherichia coli O157:H7 to UV energy.

To determine the efficacy of a UV light treatment at 253.7 nm (UVC light) on microbial growth, plates containing tryptic soy agar plus 50 ppm of nalidixic acid (TSAN) were inoculated with known concentrations of five-strain cocktails of Salmonella and Escherichia coli O157:H7 and subjected to different UVC treatments. The concentration of the cocktail inoculum was determined with TSAN prior to inoculation. Serial dilutions were carried out, and inoculation levels of 10(0) to 10(8) CFU/ ml were tested for each pathogen. Multiple replications of doses of UV light ranging from 1.5 to 30 mW/cm2 were applied to different cocktail concentrations, and doses of > 8.4 mW/cm2 resulted in a 5-log reduction of Escherichia coli O157:H7, while a 5-log reduction of Salmonella was observed with doses of > 14.5 mW/cm2. Results for both organisms yielded sigmoidal inactivation curves. UVC light is effective in reducing microbial populations of pathogens on agar surfaces.

Efficacy of detergents in removing Salmonella and Shigella spp. from the surface of fresh produce.

Fresh produce has been implicated in several foodborne disease outbreaks. Produce surfaces can be primary sites of contamination during production and handling. One approach to reduce contamination is to treat fresh produce with rinsing agents. In this study, different detergent agents were used at 22 and 40 degrees C to determine their efficacy in removing Salmonella and Shigella spp. from the surfaces of strawberries, tomatoes, and green-leaf lettuce. Produce was inoculated at 22 degrees C with a cocktail of nalidixic acid-resistant organisms (6 to 6.5 log CFU/ml). After air drying for 1 h, samples were rinsed with either 0.1% Tween 80, 0.1% sodium lauryl sulfate (SLS), or water (control) at 22 or 40 degrees C. Rinse solutions were spiral plated onto tryptic soy agar supplemented with 50 mg of nalidixic acid per liter. In trials involving strawberries and lettuce, Salmonella and Shigella were removed at levels of 4 and 3 log CFU/ml, respectively, except from Salmonella-inoculated strawberries rinsed with SLS, for which minimal removal rates were 1.5 log CFU/ml at 22 degrees C and < 1 log CFU/ml at 40 degrees C. When whole strawberries were analyzed after rinsing with SLS, few organisms were recovered. This result suggests that SLS may have a lethal or sublethal effect on Salmonella, especially when a 40 degrees C solution is used. Salmonella and Shigella removal rates for tomatoes were 1 and 1.5 log CFU/ml lower, respectively, than those for strawberries or lettuce. Overall, detergents were no more effective in removing organisms from produce than water was. The detergents examined would not constitute effective overall produce rinse treatments.

Survivability of Salmonella and Shigella spp. in sodium lauryl sulfate and tween 80 at 22 and 40 degrees C.

Fresh produce has been implicated in several foodborne disease outbreaks. A primary site of contamination during production and handling is the surface of produce. One approach to reducing contamination is to treat fresh produce with rinsing agents. Studies have examined the efficacies of detergents and other rinses in recovering pathogens from produce surfaces. The determination of how these detergents affect bacterial cells may aid in understanding the mechanisms behind their removal. This study examines the survivability of Salmonella and Shigella in two detergents. A 0.1% sodium lauryl sulfate (SLS) solution, a 0.1% Tween 80 solution, and water were inoculated with a cocktail of stationary-phase organisms (3 log CFU/ml) and incubated for up to 32 h at 22 degrees C and 40 degrees C. Samples were taken over time and plated on tryptic soy agar supplemented with 50 ppm of nalidixic acid. Salmonella survived in all solutions and exhibited significant growth in water (0.8 log CFU/ml at 22 degrees C and 1.9 log CFU/ml at 40 degrees C) and Tween 80 (1.0 log CFU/ml at 40 degrees C). Shigella survived in all solutions at 22 degrees C and exhibited a growth level of 2.0 log CFU/ml in SLS. Shigella also survived in all solutions at 40 degrees C, although its populations decreased significantly in Tween 80 over time. Elevated temperatures may allow Tween 80 to kill Shigella spp. over time. Overall, the detergents tested were not detrimental to the cells; therefore, if these solutions were to be used as produce rinse agents, they would aid in removal of organisms from surfaces rather than kill the cells.

High hydrostatic pressure processing reduces Salmonella enterica serovars in diced and whole tomatoes.

Fresh and fresh-cut tomatoes have been associated with numerous outbreaks of salmonellosis in recent years. One effective post harvest treatment to reduce Salmonella enterica in tomatoes may be high pressure processing (HPP). The objectives of the study were to determine the potential for HPP to reduce S. enterica serovars Newport, Javiana, Braenderup and Anatum in tryptic soy broth (TSB) and to determine the effect of HPP to reduce the most pressure resistant of the four serovars from fresh diced and whole tomatoes. To evaluate pressure resistance, TSB containing 8 log CFU/ml of one of the four serovars was packaged in sterile stomacher bags and subjected to one of three different pressures (350, 450 or 550MPa) for 120s. The most pressure resistant S. enterica serovar evaluated was Braenderup. Subjecting the broth culture to 350, 450 and 550MPa resulted in a 4.53, 5.74 and 7.09 log reduction in S. Braenderup, respectively. Diced tomatoes (150g) and whole red round tomatoes (approximately 150g) were inoculated with 0.1ml of 9.1 log CFU/ml S. Braenderup, and subjected to the same pressure treatments (350, 450 or 550MPa). Significant reductions of S. Braenderup concentrations in diced tomatoes (P<0.05) were seen after processing at 350 (0.46CFU/g), 450 (1.44 log CFU/g), and 550MPa (3.67 log CFU/g). In whole tomatoes, significant reductions (P<0.05) were also seen at 350 (1.41 log CFU/g), 450 (2.25 log CFU/g) and 550MPa (3.35 log CFU/g). HPP may be an effective post harvest strategy to reduce low levels of S. enterica contamination in whole and diced tomatoes.

Recovery of Salmonella spp. from raw produce surfaces using ultrasonication.

Fresh fruits and vegetables have been increasingly associated with outbreaks of foodborne illness. Microorganisms on the surface of raw produce may be difficult to remove for decontamination or microbial sampling due to entrapped or attached cells and porous surfaces. The objective of this study was to determine if ultrasonic treatment using 40 kHz with varying temperatures and agitation times can enhance removal and recovery of Salmonella spp. from raw produce surfaces. Strawberry, apple, and cantaloupe surfaces were spot inoculated with a fivestrain cocktail of nalidixic acid-resistant Salmonella spp. Produce were immersed in 0.1% buffered peptone water in either a Whirl-Pak bag for manual shaking (60 sec) or a sterile beaker for ultrasonic treatment (60 or 120 sec). Diluent temperatures of either 25 degrees C or 40 degrees C were used with these sampling protocols. Diluents were spiral plated onto tryptic soy agar supplemented with 50 ppm of nalidixic acid. No significant differences were observed between each Salmonella recovery method for each produce type. In this study, ultrasonic treatment using 40 kHz did not enhance recovery of Salmonella spp. from produce surfaces. The ultrasonic frequency, temperatures, and times used in this study did not enhance or diminish bacterial recovery. Additional research is still needed to determine the efficacy of other ultrasonic frequencies, diluents, and diluent temperatures for enhancing the recovery and enumeration of Salmonella spp. and other microorganisms from raw produce surfaces.