Department of Microbiology, Nicolaus Copernicus University in Toruń, L. Rydygier Collegium Medicum in Bydgoszcz, 9 M. Skłodowska-Curie St., 85-094 Bydgoszcz, Poland.
Department of Microbiology, Nicolaus Copernicus University in Toruń, L. Rydygier Collegium Medicum in Bydgoszcz, 9 M. Skłodowska-Curie St., 85-094 Bydgoszcz, Poland.
Int J Food Microbiol. 2019 May 2;296:75-82. doi: 10.1016/j.ijfoodmicro.2019.02.021. Epub 2019 Mar 1.
The aim of the study was to analyze the contamination of mold cheese (Brie, Camembert, Gorgonzola, Munster and Roquefort) with Listeria spp. and assessment of culturable cells number recovered from the biofilm formed on the surface of stainless steel by obtained strains. Identified isolates (MALDI TOF MS technique) were subjected to susceptibility testing (disk-diffusion method) and their genetic similarity (PFGE method), ability to form biofilm (quantitative method), biofilm dry weight, and biofilm survival on stainless steel were evaluated. Out of 250 samples of cheese 26 (10.4%) were Listeria spp. positive, including 15 isolates (6.0% of samples) of L. monocytogenes, 7 isolates of L. innocua (2.8% of samples) and 4 isolates of L. welshimeri species (1.6% of samples). Of the 26 isolates tested, 22 strains were genetically different. It was shown that L. innocua and L. welshimeri strains were sensitive to all antibiotics tested, while two (16.7%) L. monocytogenes strains were resistant to penicillin and one (8.3%) to erythromycin. L. monocytogenes formed biofilm most intensively on stainless steel, while L. welshimeri the least effectively. The median of bacteria number recovered from the biofilm for L. monocytogenes was 6.81 log CFU × cm, for L. innocua - 5.63 log CFU × cm, and for L. welshimeri - 4.93 log CFU × cm. The survival in the biofilm of Listeria spp. strains decreased along with the increase in a storage temperature of steel coupons. The longest survival time was reported at 4 °C, i.e. 47.58-124.41 days, with an elimination rate of 0.06-0.13 log CFU × day. Collectively, L. monocytogenes is the most prevalent species of Listeria genus in the mold cheese. The ability of L. monocytogenes strains to form biofilm on stainless steel and survive in the food processing environment increases chance of the secondary contamination of food posing risk to the consumer health.
本研究的目的是分析 mold cheese（布里干酪、卡门培尔干酪、戈贡佐拉干酪、芒斯特干酪和罗克福干酪）中霉菌的污染情况，并评估从不锈钢表面生物膜中回收的可培养细胞数量。通过获得的菌株，对鉴定出的分离株（MALDI TOF MS 技术）进行药敏试验（纸片扩散法）和遗传相似性（PFGE 法）、生物膜形成能力（定量法）、生物膜干重以及不锈钢上生物膜的存活能力进行评估。在 250 份奶酪样本中，有 26 份（10.4%）为李斯特菌属阳性，其中包括 15 株（占样本的 6.0%）李斯特菌单核细胞增生李斯特菌、7 株无害李斯特菌（占样本的 2.8%）和 4 株威尔斯李斯特菌（占样本的 1.6%）。在 26 株被检测的分离株中，有 22 株具有不同的遗传特性。结果表明，无害李斯特菌和威尔斯李斯特菌对所有测试的抗生素均敏感，而 2 株（占 16.7%）单核细胞增生李斯特菌对青霉素耐药，1 株（占 8.3%）对红霉素耐药。单核细胞增生李斯特菌在不锈钢上形成的生物膜最密集，而威尔斯李斯特菌则效果最差。从生物膜中回收的细菌数量中位数，单核细胞增生李斯特菌为 6.81 log CFU×cm，无害李斯特菌为 5.63 log CFU×cm，威尔斯李斯特菌为 4.93 log CFU×cm。李斯特菌属菌株在钢片储存温度升高时，其在生物膜中的存活能力下降。在 4°C 下报告的存活时间最长，为 47.58-124.41 天，消除率为 0.06-0.13 log CFU×天。总的来说，单核细胞增生李斯特菌是 mold cheese 中最常见的李斯特菌属物种。单核细胞增生李斯特菌在不锈钢上形成生物膜并在食品加工环境中存活的能力增加了二次污染食品的机会，从而对消费者健康构成威胁。
