Department of Microbiology, Ludwik Rydygier Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University, Toruń, Poland.
Department of Food Hygiene and Consumer Health, Wrocław University of Environmental and Life Sciences, Wrocław, Poland.
BMC Microbiol. 2023 Jan 24;23(1):27. doi: 10.1186/s12866-023-02766-4.
Listeria monocytogenes are Gram-positive rods, which are the etiological factor of listeriosis. L. monocytogenes quickly adapts to changing environmental conditions. Since the main source of rods is food, its elimination from the production line is a priority. The study aimed to evaluate the influence of selected stress factors on the growth and survival of L. monocytogenes strains isolated from food products and clinical material.
We distinguished fifty genetically different strains of L. monocytogenes (PFGE method). Sixty-two percent of the tested strains represented 1/2a-3a serogroup. Sixty percent of the rods possessed ten examined virulence genes (fbpA, plcA, hlyA, plcB, inlB, actA, iap, inlA, mpl, prfA). Listeria Pathogenicity Island 1 (LIPI-1) was demonstrated among 38 (76.0%) strains. Majority (92.0%) of strains (46) were sensitive to all examined antibiotics. The most effective concentration of bacteriophage (inhibiting the growth of 22 strains; 44.0%) was 5 × 10 PFU. In turn, the concentration of 8% of NaCl was enough to inhibit the growth of 31 strains (62.0%). The clinical strain tolerated the broadest pH range (3 to 10). Five strains survived the 60-min exposure to 70˚C, whereas all were alive at each time stage of the cold stress experiment. During the stress of cyclic freezing-defrosting, an increase in the number of bacteria was shown after the first cycle, and a decrease was only observed after cycle 3. The least sensitive to low nutrients content were strains isolated from frozen food. The high BHI concentration promoted the growth of all groups.
Data on survival in stress conditions can form the basis for one of the hypotheses explaining the formation of persistent strains. Such studies are also helpful for planning appropriate hygiene strategies within the food industry.
单核细胞增生李斯特菌是革兰氏阳性杆菌，是李斯特菌病的病因。单核细胞增生李斯特菌能迅速适应环境条件的变化。由于其主要来源是食物，因此从生产线上消除它是当务之急。本研究旨在评估选定应激因素对从食品和临床材料中分离出的单核细胞增生李斯特菌菌株的生长和存活的影响。
我们区分了五十种不同的单核细胞增生李斯特菌遗传菌株（PFGE 方法）。62%的测试菌株代表 1/2a-3a 血清群。60%的杆菌具有十个检查的毒力基因（fbpA、plcA、hlyA、plcB、inlB、actA、iap、inlA、mpl、prfA）。38 株（76.0%）单核细胞增生李斯特菌菌株中存在李斯特菌致病性岛 1（LIPI-1）。92.0%（46 株）的菌株对所有检查的抗生素均敏感。噬菌体的最有效浓度（抑制 22 株菌的生长；44.0%）为 5×10 PFU。相反，8%的 NaCl 浓度足以抑制 31 株菌（62.0%）的生长。临床菌株耐受的 pH 值范围最广（3 至 10）。5 株菌在 70˚C 下暴露 60 分钟后存活，而在冷应激实验的每个时间阶段，所有菌均存活。在循环冷冻-解冻应激中，在第一个循环后观察到细菌数量增加，仅在第三个循环后观察到减少。对冷冻食品中分离出的菌株来说，低营养含量最不敏感。高 BHI 浓度促进了所有组的生长。
对压力条件下存活的数据可以作为解释持续菌株形成的假设之一的基础。这些研究还有助于在食品工业中规划适当的卫生策略。
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