Food Microbiology and Hygiene, National Food Institute (DTU Food), Technical University of Denmark, Kgs. Lyngby, Denmark.
Food Microbiology and Hygiene, National Food Institute (DTU Food), Technical University of Denmark, Kgs. Lyngby, Denmark.
J Food Prot. 2024 Nov;87(11):100367. doi: 10.1016/j.jfp.2024.100367. Epub 2024 Sep 30.
Prevalence, toxin gene profiles, lactose fermentation, and growth responses of B. cereus sensu lato subgroups in various dairy and dairy alternative products and ingredients were studied to identify relevant isolates for challenge testing and model development to predict and manage growth responses. Out of 71 examined products or ingredients, 51 B. cereus s.l. isolates were obtained from 35 positive samples (49% prevalence). These 51 isolates along with 18 additional dairy isolates and 12 B. cereus s.l. reference strains were identified using MALDI-TOF. The 81 isolates were further characterized by panC sequencing, testing for cold shock and toxin genes (cspA; hbl, nhe, CytK and ces), lactose fermentation, and study of growth rates (µ) under various conditions (45 °C, 10 °C, 6% NaCl, pH 5.1), resulting in 298 µ-values. These conditions were selected to differentiate mesophilic and psychrotolerant strains and to identify tolerant isolates. Dairy powders (83%), pasteurized upconcentrated cheese whey (43%), and cheeses (42%) had the highest prevalences of B. cereus s.l. and the highest concentrations in positive samples (5-100 CFU/g or ml). The panC groups II, III, IV, VI, and VIII were detected among the dairy isolates, with 97% harboring one or more toxin genes. Lactose fermentation was observed in 42% of isolates, with lactose-fermenting B. cereus s.l. isolates of panC groups III and IV dominant in dairy powders. Growth rates of B. cereus s.l. varied considerably, among and within panC groups of the dairy isolates. Based on the highest growth rates at 45 °C, 10 °C, 6% NaCl, pH 5.1, panC group membership, toxin genes profiles, and lactose fermentation ability, two cocktails of "mesophilic" or "psychrotolerant" isolates were selected. These strain cocktails can be used in future challenge testing and predictive food microbiology studies to evaluate and manage the growth of B. cereus s.l. in dairy products and ingredients.
研究了各种乳制品和乳制品替代品及成分中 B. cereus sensu lato 亚群的流行情况、毒素基因谱、乳糖发酵和生长反应，以确定相关分离株用于挑战测试和模型开发，以预测和管理生长反应。在检查的 71 种产品或成分中，从 35 个阳性样本中获得了 51 株 B. cereus s.l. 分离株（流行率为 49%）。这些 51 株分离株以及 18 株额外的乳制品分离株和 12 株 B. cereus s.l. 参考菌株，使用 MALDI-TOF 进行了鉴定。通过 panC 测序进一步鉴定了 81 株分离株，检测了冷休克和毒素基因（cspA；hbl、nhe、CytK 和 ces）、乳糖发酵以及在不同条件（45°C、10°C、6%NaCl、pH5.1）下的生长速率（µ），共获得 298 个µ值。这些条件的选择是为了区分中温菌和耐冷菌，并确定耐受分离株。乳制品粉末（83%）、巴氏杀菌浓缩奶酪乳清（43%）和奶酪（42%）中 B. cereus s.l. 的流行率最高，阳性样本中的浓度最高（5-100 CFU/g 或 ml）。在乳制品分离株中检测到 panC 组 II、III、IV、VI 和 VIII，其中 97%携带一个或多个毒素基因。42%的分离株能够发酵乳糖，乳制品粉末中 panC 组 III 和 IV 的乳糖发酵 B. cereus s.l. 分离株占主导地位。乳制品分离株的 B. cereus s.l. 生长速率差异很大，在 panC 组内和组间均有差异。根据 45°C、10°C、6%NaCl、pH5.1 时的最高生长速率、panC 组归属、毒素基因谱和乳糖发酵能力，选择了两组“中温”或“耐冷”分离株的鸡尾酒。这些菌株鸡尾酒可用于未来的挑战测试和预测食品微生物学研究，以评估和管理乳制品和乳制品成分中 B. cereus s.l. 的生长。
