Foodborne

The aim of the current work was to assess the influence of two temperatures, 4°C and 24°C, on pH and water activity and their association with Brucella melitensis survival during the traditional manufacture of ripened goat cheese. Raw milk from a brucellosis-free goat herd was used for the manufacture of ripened cheese. The cheese was inoculated with 5×10(9) of the B. melitensis 16M strain during the tempering stage. The cheeses were matured for 5, 20, and 50 days at both temperatures. To assess Brucella survival, the pH and a(w) were recorded at each stage of the process (curd cutting, draining whey, immersion in brine, ripening I, ripening II, and ripening III). B. melitensis was detected at ripening stage III (1×10(3) colony-forming unit [CFU]/mL) from cheeses matured at 4°C with a pH of 5.0 and a(w) of 0.90, and at a ripening stage II (1×10(4) CFU/mL) from cheeses ripened at 24°C with a pH of 4.0 and a(w) of 0.89. The remaining stages were free from the inoculated pathogen. In addition, viable B. melitensis was recovered in significant amounts (1-2×10(6) CFU/mL) from the whey fractions of both types of cheese ripened at 24°C and 4°C. These results revealed the effects of high temperature (24°C vs. 4°C) on the low pH (4) and a(w) (0.89) that appeared to be associated with the suppression of B. melitensis at the early stages of cheese ripening. In the ripened goat cheeses, B. melitensis survived under a precise combination of temperature during maturation, ripening time, and a(w) in the manufacturing process.

This study used integrated surveillance data to assess the seasonality in retail chicken contamination and of human activities and their role on the seasonality of human endemic salmonellosis. From June 2005 to May 2008, reported cases of salmonellosis were followed-up comprehensively using a standardized questionnaire, and 616 retail chicken breasts were systematically tested for Salmonella, in one Canadian community. Poisson regression was used to model seasonality of human cases, Salmonella in retail chicken, and to assess the relationship between these and selected meteorological variables. The case-case approach was used to compare the activities of salmonellosis cases that occurred during the summer peak to the other cases. There were 216 human endemic salmonellosis cases (incidence rate: 14.7 cases/100,000 person-years), predominantly of Typhimurium and Enteritidis serotypes (28.4% and 20.8%, respectively). The monthly distribution of cases was associated with ambient temperature (p < 0.001) with a significant seasonal peak in June (p = 0.03) and July (p = 0.0005), but it was not associated with precipitation (p = 0.38). Several activities reported by cases tended to be more frequent during summer. Particularly, attending a barbeque and gardening within the 3 days before the disease onset were two significant risk factors for salmonellosis in June or July compared with the salmonellosis cases that occurred in the other months. Out of all chicken samples, 185 (30%) tested positive for Salmonella spp., Kentucky being the dominant serotype (44.3% of positive samples). The monthly proportion of positive chicken samples showed no seasonal variations (p = 0.30) and was not associated with the monthly count of human cases (p = 0.99). In conclusion, even though evidence generally supports chicken as a primary vehicle of Salmonella to humans, the contamination of retail chicken was not driving the seasonality in human salmonellosis. Attending a barbeque or gardening during the hotter months of the year should be further assessed for their risk.

This study used integrated surveillance data to assess the seasonality in retail chicken contamination and of human activities and their role on the seasonality of human endemic salmonellosis. From June 2005 to May 2008, reported cases of salmonellosis ...

This study conducted microbiological assessment in tunnel style strawberry greenhouses and packaging centers and suggested recommendations to establish a good agricultural practice for strawberry production. The samples from irrigation water, workers' gloves, harvest bins, soil, strawberry leaves and strawberries in greenhouses, packers' gloves, conveyor belts, packaging tables, and door knobs of entrances in packaging centers were collected. Bacterial cell counts of aerobic plate counts, coliforms, Escherichia coli, E. coli O157:H7, Salmonella, Staphylococcus aureus, and Bacillus cereus were then enumerated on appropriate selective media. In general, bacterial populations were similar (p ≥ 0.05) among strawberry greenhouses but not among packaging houses. E. coli and E. coli O157:H7 were negative in all samples, and low levels of Salmonella and B. cereus were detected. However, high bacterial cell counts of aerobic plate counts, coliforms, and S. aureus were found in most samples. These results suggest that food safety practice in strawberry greenhouses and packaging centers should be improved, and the results may be useful in the establishment of a good agricultural practice system for strawberry production.

Destructive and nondestructive sampling procedures were compared for Escherichia coli and Salmonella spp. detection in 60 fresh chicken carcasses, which were submitted to the following sampling procedures: rinsing, skin swabbing, tissue excision, ...

In the present study, we investigated the effect of exposure to A static magnetic field (SMF) on cell growth, viability, and gene expression of Salmonella enterica subsp. enterica serovar Hadar. Our results indicated that SMF exposure (200 mT, 13 hours) failed to alter cellular growth but induced a decrease of colony-forming units (CFU) between 3 and 6 hours followed by an increase from 6 to 9 hours. The analysis of the differential expression of rpoA, dnaK, katN, and 16S rRNA genes under SMF exposure (200 mT, 10 hours) showed that the expression level of the 16S rRNA mRNA remained stable during the exposure and can thus be used as a reference gene for the analysis on the differential gene expression of Salmonella Hadar. Interestingly, mRNAs of rpoA, katN, and dnaK genes were over-expressed following 10 hours of SMF exposure (200 mT). These data suggest a possible stress response of Salmonella Hadar to static magnetic field.

We report here the results of the survey of antimicrobial resistance in 148 serotype Typhimurium strains isolated from cattle in France from 2002 to 2007 and displaying more than two antimicrobial resistances. Salmonella enterica serotype Typhimurium of definitive phage type 104 strains that are commonly resistant to ampicillin-amoxicillin, chloramphenicol-florfenicol, streptomycin-spectinomycin, sulfonamides, and tetracycline (ACSSuT phenotype) harbored resistance genes clustered on a complex class 1 integron In104 of the Salmonella genomic island 1 (SGI1). In our isolates, the most common antimicrobial resistance pattern was ACSSuT (77.7%) or ACSSuT combined to additional resistances. SGI1 was detected in 143 strains and constituted thus the main structure involved in resistance to antimicrobials in these strains. In spite of the high recombination potential of In104, SGI1 variability was quite limited among these strains since only two SGI1 variants, SGI1-B and SGI1-C, were identified. One hundred and thirty-eight out of the 143 SGI1-positive isolates belonged to the DT104 complex. Pulsed-field gel electrophoresis profile A was the most prevalent in 135 SGI1-positive isolates, confirming the diffusion of the DT104 clone. However, changes in phages susceptibility have occurred in three serotype Typhimurium strains of phage type DT12, as they displayed the same pulsed-field gel electrophoresis profile as the SGI1-positive serotype Typhimurium DT104. No variant harboring an additional resistance gene was identified, but the risk of recombination between SGI1 and any other mobile structure carrying other antimicrobial resistance genes is still an issue in serotype Typhimurium.

To increase understanding of community-acquired resistance, stool samples from 477 nonhospitalized persons in Maryland and Michigan, from 2004 to 2008, were screened for ceftriaxone resistance. Seven (1.5%) yielded ceftriaxone-resistant Escherichia coli; one isolate was resistant to all eight antimicrobial classes routinely tested: aminoglycosides, β-lactam/β-lactamase inhibitor combinations, cephems, penicillins, folate pathway inhibitors, phenicols, quinolones, and tetracyclines. The extensively resistant isolate was from a 50-year-old woman who denied antimicrobial use, hospitalization, or international travel within 6 months. Meat (beef, chicken, and pork) and eggs were consumed within 1 month before stool collection. Further studies are warranted to understand potential sources, including the food supply, of resistant E. coli.