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Whole and cut cantaloupes have been implicated as vehicles in foodborne illness outbreaks of norovirus, salmonellosis, and listeriosis. Preparation methods that minimize pathogen transfer from external surfaces to the edible tissue are needed. Two preparation methods were compared for the transfer of Listeria monocytogenes, Salmonella entericaserovar Typhimurium LT2, murine norovirus, and Tulane virus from inoculated cantaloupe rinds to edible tissue and preparation surfaces. For the first method, cantaloupes were cut into eighths, and edible tissue was separated from the rind and cubed with the same knife used to open the cantaloupes. For the second method, cantaloupes were scored with a knife around the circumference sufficient to allow manual separation of the cantaloupes into halves. Edible tissue was scooped with a spoon and did not contact the preparation surface touched by the rind. Bacteria and virus were recovered from the rinds, preparation surfaces, and edible tissue and enumerated by culture methods and reverse transcription, quantitative PCR, respectively. Standard plate counts were determined throughout refrigerated storage of cantaloupe tissue. Cut method 2 yielded approximately 1 log lower recovery of L. monocytogenesand SalmonellaTyphimurium from edible tissue, depending on the medium in which the bacteria were inoculated. A slight reduction was observed in murine norovirus recovered from edible tissue by cut method 2. The Tulane virus was detected in approximately half of the sampled cantaloupe tissue and only at very low levels. Aerobic mesophilic colony counts were lower through day 6 of storage for buffered peptone water–inoculated cantaloupes prepared by cut method 2. No differences were observed in environmental contamination as a function of cutting method. Although small reductions in contamination of edible tissue were observed for cut method 2, the extent of microbial transfer underscores the importance of preventing contamination of whole cantaloupes.

Vibrio parahaemolyticusATCC 43996 was grown at 15°C for 53 h, 20°C for 24 h, 25°C for 12 h, 30°C for 9 h, 35°C for 9 h, or 40°C for 6 h to early stationary phase. Oyster meats were blended, autoclaved at 121°C for 15 min, inoculated with V. parahaemolyticus,and pressure treated at 250 MPa for 2 and 3 min and at 300 MPa for 1 and 2 min at 21°C. Overall, growth temperatures of 20 and 40°C yielded the greatest pressure resistance in V. parahaemolyticus. The effects of salt concentration and H2O2-degrading compounds on the recovery of V. parahaemolyticusalso were investigated. Sterile oyster meats were inoculated with V. parahaemolyticusand treated at 250 MPa for 1, 2, or 3 min at 21°C. These meats were then blended with 0.1% peptone water supplemented with 0.5 to 1.5% NaCl and plated on tryptic soy agar (TSA) supplemented with 0 to 3.5% NaCl. For recovery of pressure-injured cells, peptone water with 1% NaCl and TSA with 0.5% NaCl were the best diluent and plating medium, respectively. Addition of sodium pyruvate (0.05 to 0.2%) or catalase (8 to 32 U/ml) did not increase the recovery of V. parahaemolyticusafter pressure treatment. The effect of incubation temperature and gas atmosphere on the recovery of V. parahaemolyticusafter pressure treatment also was determined. Aerobic incubation at 30°C resulted in the highest recovery of V. parahaemolyticusin sterile oyster meats. The 30°C incubation temperature was also the optimum temperature for recovery of V. parahaemolyticusin pressure-treated live oysters. The results of this study indicate that the growth conditions for V. parahaemolyticusbefore and after high hydrostatic pressure treatment should be taken into consideration when assessing the efficacy of pressure inactivation.

The prevalence, size, genome, and life cycle of Eimeria acervulinamake this organism a good surrogate for Cyclospora cayetanensis, a protozoan that causes gastroenteritis in humans, including recent outbreaks in the United States and Canada associated with contaminated raspberries and basil. Laboratory studies of C. cayetanensisare difficult because of the lack of readily available oocysts and of infection models and assays. UV radiation and high-hydrostatic-pressure processing (HPP) are both safe technologies with potential for use on fresh produce. Raspberries and basil were inoculated with sporulated E. acervulinaoocysts at high (106oocysts) and low (104oocysts) levels, and inoculated and control produce were treated with UV (up to 261 mW/cm2) or HPP (550 MPa at 40°C for 2 min). Oocysts recovered from produce were fed to 3-week-old broiler chickens, which were scored for weight gain, oocyst shedding, and lesions at 6 days postinoculation. Oocysts exhibited enhanced excystation on raspberries but not on basil. Birds fed oocysts from UV-treated raspberries had reduced infection rates, which varied with oocyst inoculum level and UV intensity. Birds fed oocysts from UV-treated raspberries (104oocysts) were asymptomatic but shed oocysts, and birds fed oocysts from UV-treated basil (104oocysts) were asymptomatic and did not shed oocysts. Birds fed oocysts from HPP-treated raspberries and basil were asymptomatic and did not shed oocysts. These results suggest that UV radiation and HPP may be used to reduce the risk for cyclosporiasis infection associated with produce. Both treatments yielded healthy animals; however, HPP was more effective, as indicated by results for produce with higher contamination levels.

BAX, a polymerase chain reaction (PCR)–based pathogen detection system, was used to survey retail sprouts and mushrooms for contamination with Escherichia coliO157:H7, Salmonella, Listeriaspp., and Listeria monocytogenes. No Salmonellaor E. coliO157:H7 was detected in the 202 mushroom and 206 alfalfa sprout samples screened. L. monocytogeneswas detected in one sprout sample, and seven additional sprout samples tested positive for the genus Listeria. BAX also detected Listeriaspecies in 17 of the mushroom samples. Only 6 of 850 PCR assays (0.7%) failed to amplify control DNA, and therefore reagent failures and the inhibition of PCR by plant compounds were rare. The sensitivity of the detection system was evaluated by assaying samples inoculated with 10 CFU of each of the pathogens. One hundred seventy-two alfalfa sprout samples were inoculated with E. coliO157:H7, and two sets of 130 samples were experimentally contaminated with SalmonellaEnteritidis and L. monocytogenes. The frequency of detection depended on the protocols used for inoculation and culturing. Inoculation of samples with approximately 10 CFU from frozen stocks yielded detection rates of 87.5 and 94.5% for L. monocytogenesand SalmonellaEnteritidis, respectively, in mushrooms. The corresponding rates for alfalfa sprouts were 94.5 and 76.3%. The E. coliO157:H7 detection rate was 100% for mushrooms but only 48.6% for sprouts when standard BAX culture protocols were used. The substitution of an overnight incubation in modified E. colimedium for the 3-h brain heart infusion incubation increased the rate of E. coliO157:H7 detection to 75% for experimentally contaminated sprouts. The detection rate was 100% when E. coliO157:H7 cells from a fresh overnight culture were used for the inoculation. Test sensitivity is therefore influenced by the type of produce involved and is probably related to the growth of pathogens in the resuscitation and enrichment media.

A polymerase chain reaction (PCR)-based detection system, BAX, was evaluated for its sensitivity in detecting SalmonellaEnteritidis, Escherichia coliO157:H7, Listeriasp., and Listeria monocytogeneson fresh produce. Fifteen different types of produce (alfalfa sprouts, green peppers, parsley, white cabbage, radishes, onions, carrots, mushrooms, leaf lettuce, tomatoes, strawberries, cantaloupe, mango, apples, and oranges) were inoculated, in separate studies, with SalmonellaEnteritidis, E. coliO157:H7, and L. monocytogenesdown to the predicted level of 1 CFU per 25-g sample. Detection by BAX was compared to recovery of the inoculated bacteria by culture methods according to the Food and Drug Administration's (FDA) Bacteriological Analytical Manual (BAM). BAX was essentially as sensitive as the culture-based method in detecting SalmonellaEnteritidis and L. monocytogenesand more sensitive than the culture-based method for the detection of E. coliO157:H7 on green pepper, carrot, radish, and sprout samples. Detection of the pathogenic bacteria in samples spiked with a predicted number of less than 10 CFU was possible for most produce samples, but both methods failed to detect L. monocytogeneson carrot samples and one of two mushroom and onion samples spiked with less than 100 CFU. Both BAX and the culture method were also unable to consistently recover low numbers of E. coliO157:H7 from alfalfa sprouts. The PCR method allowed detection of SalmonellaEnteritidis, E. coliO157:H7, and L. monocytogenesat least 2 days earlier than the conventional culture methods.