Survival and germination of Clostridium perfringens spores during heating and cooling of ground pork

A survey of a blown pack spoilage produced by Clostridium perfringens in vacuum-packaged wurstel

Three hundred Clostridium strains were isolated from spoiled wurstels and were identified by traditional and molecular methods as Clostridium perfringens. The phenotypic characteristics of the strains were studied. All the strains produced acetic and butyric acids and enterotoxin. C. perfringens grew in the spoiled wurstels because it was present in raw meat (Lot 150) at a level of 3.2 log CFU/g due to an unchecked cooling phase that took 28 h to decrease the temperature of the wurstels from 60 to 9-10 °C, which is the lower limit for C. perfringens growth. During the 28 h of cooling, the concentration of C. perfringens increased to 6.5 CFU/g. It was concluded that its presence and the long cooling time were the main factors responsible for the spoilage. Wurstels intentionally made with contaminated meat (3 log CFU/g) but cooled after cooking for 17 h to 9 °C did not support C. perfringens growth; consequently, these wurstels remained unspoiled. The packages of the spoiled wurstels were blown, and the products were soft (soggy), textureless and had the odour of acetic acid, ethanol and sulfur.

Near-infrared spectroscopy coupled with chemometrics algorithms for the quantitative determination of the germinability of Clostridium perfringens in four different matrices

Clostridium perfringens (C. perfringens) has the ability to form metabolically-dormant spores that can survive food preservation processes and cause food spoilage and foodborne safety risks upon germination outgrowth. This study was conducted to investigate the effects of different AGFK concentrations (0, 50, 100, 200 mM/mL) on the spore germination of C. perfringens in four matrices, including Tris-HCl, FTG, milk, and chicken soup. C. perfringens spore germinability was investigated using near infrared spectroscopy (NIRS) combined with chemometrics. The spore germination rate (S), the OD₆₀₀%, and the Ca²⁺-DPA% were measured using traditional spore germination methods. The results of spore germination assays showed that the optimum germination rate was obtained using 100 mM/L concentrations of AGFK in the FTG medium, and the S, OD₆₀₀% and Ca²⁺-DPA% were 98.6%, 59.3% and 95%, respectively. The best prediction models for the S, OD₆₀₀% and Ca²⁺-DPA% were obtained using SNV as the preprocessing method for the original spectra, with the competitive adaptive weighted resampling method (CARS) as the characteristic variables related to the selected spore germination methods from NIRS data. The results of the S showed that the optimum model was built by CARS-PLSR (RMSEV = 0.745, R_c = 0.897, RMSEP = 0.769, R_p = 0.883). For the OD₆₀₀%, interval partial least squares regression (CARS-siPLS) was performed to optimize the models. The calibration yielded acceptable results (RMSEV = 0.218, R_c = 0.879, RMSEP = 0.257, R_p = 0.845). For the Ca²⁺-DPA%, the optimum model with CARS-siPLS yielded acceptable results (RMSEV = 44.7, R_c = 0.883, RMSEP = 50.2, R_p = 0.872). This indicated that quantitative determinations of the germinability of C. perfringens spores using NIR technology is feasible. A new method based on NIR was provided for rapid, automatic, and non-destructive determination of the germinability of C. perfringens spores.

Prevalence, toxin gene profile, antibiotic resistance, and molecular characterization of Clostridium perfringens from diarrheic and non-diarrheic dogs in Korea

Clostridium perfringens causes diarrhea and other diseases in animals and humans. We investigated the prevalence, toxin gene profiles, and antibiotic resistance of C. perfringens isolated from diarrheic dogs (DD) and non-diarrheic dogs (ND) in two animal hospitals in Seoul, Korea. Fecal samples were collected from clinically DD (n = 49) and ND (n = 34). C. perfringens was isolated from 31 of 49 DD (63.3%) and 21 of 34 ND dogs (61.8%). All C. perfringens strains were positive for the α toxin gene, but not for the β, ε, or ι toxin genes; therefore, all strains were identified as type A C. perfringens. All isolates were cpe-negative, whereas the β2 toxin gene was identified in 83.9% and 61.9% of isolates from DD and ND, respectively. Most isolates were susceptible to ampicillin (94%), chloramphenicol (92%), metronidazole (100%), moxifloxacin (96%), and imipenem (100%). However, 25.0% and 21.2% of isolates were resistant to tetracycline and clindamycin, respectively. Molecular subtyping of the isolated strains was performed by using pulsed-field gel electrophoresis. Fifty-two isolates were classified into 48 pulsotypes based on more than 90% similarity of banding patterns. No notable differences were observed among the isolates from DD and ND.

Inhibition of Clostridium perfringens Growth during Extended Cooling of Cooked Uncured Roast Turkey and Roast Beef Using a Concentrated Buffered Vinegar Product and a Buffered Vinegar Product

This research was conducted to evaluate the effectiveness of a concentrated buffered vinegar product (CBV) and a simple buffered vinegar product (BV) for controlling Clostridium perfringens outgrowth during extended cooling times of ready-to-eat roast turkey and roast beef. Whole turkey breasts and beef inside rounds were injected with a typical brine and then ground and mixed with CBV (0.0, 2.01, 2.70, and 3.30% [w/w]) or BV (0.0, 1.75, 2.25, and 3.75% [w/w]) and a three-strain C. perfringens spore cocktail to a detectable level of ca. 2 to 3 log CFU/g. The meat was divided into 10-g portions, vacuum packaged, and stored frozen until tested. The turkey and beef were cooked in a programmable water bath to 71.6°C (160.8°F) in 5 h and to 57.2°C (135°F) in 6 h, respectively. The cooked turkey and beef were then cooled exponentially from 48.9 to 12.8°C (120 and 55°F) in 6, 9, 12, 15, and 18 h for the five cooling treatments. The cooling continued until the temperature reached 4.4°C (40°F). C. perfringens counts were determined at 54.4°C (130°F) and 4.4°C. CBV at 2.01% effectively limited C. perfringens growth in turkey to ≤1 log CFU/g with up to a 9-h cooling treatment, and 2.70 and 3.30% solutions were effective with up to the 18-h cooling treatment. BV had an inhibitory effect on C. perfringens outgrowth in beef but did not limit growth to ≤1 log CFU/g at any concentration tested for any of the cooling treatments.

Behavior and Inactivation of Enterotoxin-Positive Clostridium perfringens in Pork Picadillo and Tamales Filled with Pork Picadillo under Different Cooking, Storage, and Reheating Conditions

This study analyzed the behavior of Clostridium perfringens in individual ingredients and tamales containing different pathogen concentrations upon exposure to different temperatures and methods of cooking, storage, and reheating. In ground pork, C. perfringens cells were inactivated when exposed to 95°C for 30 min. Three lots of picadillo inoculated with 0, 3, and 5 log CFU/g C. perfringens cells, respectively, were exposed to different storage temperatures. At 20°C, cell counts increased 1 log in all lots, whereas at 8°C, counts decreased by 2 log. Four lots of tamales prepared with picadillo inoculated with 0, 2, 3, and 7 log CFU/g prior to the final cooking step exhibited no surviving cells (91°C for 90, 45, or 35 min). Four lots of tamales were inoculated after cooking with concentrations of 0, 0.6, 4, and 6 log CFU/g of the pathogen and then stored at different temperatures. In these preparations, after 24 h at 20°C, the count increased by 1.4, 1.7, and 1.8 log in the tamales inoculated with 0.6, 4, and 6 log inoculum, respectively. When they were stored at 8°C for 24 h, enumerations decreased to <1, 2.5, and 1.9 log in the tamales inoculated with 0.6, 4, and 6 log of C. perfringens cells, respectively. However, when the lots were exposed to 20°C and then 8°C, 0.8, 1.8, and 2.4 log changes were observed for the tamales inoculated with 0.6, 4, and 6 log, respectively. Microwaving, steaming, and frying to reheat tamales inoculated with 6 log CFU/g C. perfringens cells showed that the pathogen was inactivated after 2 min of exposure in the microwave and after 5 min of exposure to steam. In contrast, no inactivation was observed after 5 min of frying. The tamales inoculated with spores (7 log most probable number [MPN]/g) showed a decrease of 2 log after steaming or frying, and no survival was observed after microwaving. Tamales inoculated with spores (7 log MPN/g) after cooking were susceptible to microwaves, but 2.4 and 255 MPN/g remained after frying and steaming, respectively.

Clostridium perfringens: Comparative effects of heat and osmotic stress on non-enterotoxigenic and enterotoxigenic strains

Clostridium perfringens isolates associated with food poisoning carries a chromosomal cpe gene, while non-foodborne human gastrointestinal disease isolates carry a plasmid cpe gene. The enterotoxigenic strains tested produced vegetative cells and spores with significantly higher resistance than non-enterotoxigenic strains. These results suggest that the vegetative cells and spores have a competitive advantage over non-enterotoxigenic strains. However, no explanation has been provided for the significant associations between chromosomal cpe genotypes with the high resistance, which could explain the strong relationship between chromosomal cpe isolates and C. perfringens type A food poisoning. Here, we analyse the action of physical and chemical agent on non-enterotoxigenic and enterotoxigenic regional strains. And this study tested the relationship between the sensitivities of spores and their levels SASPs (small acid soluble proteins) production in the same strains examined.