Sadiq Faizan A, Flint Steve, Yuan Lei, Li Yun, Liu TongJie, He GuoQing
College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China.
School of Food and Nutrition, Massey University, Private Bag 11 222, Palmerston North, New Zealand.
Int J Food Microbiol. 2017 Dec 4;262:89-98. doi: 10.1016/j.ijfoodmicro.2017.09.015. Epub 2017 Sep 27.
Biofilms on the surface of dairy manufacturing plants are potential reservoirs of microbial contamination. These microbial aggregates may harbour pathogenic and spoilage organisms which contaminate dairy products. The biofilm forming capacity of many spore forming isolates of dairy origin has not been given much attention. The present study explored the biofilm forming potential of 148 isolates, comprising mesophilic and thermophilic bacteria, with particular emphasis on Bacillus licheniformis on polystyrene and stainless steel (SS) surfaces. We concluded that only four species are of significance for biofilm development on the surface of SS in the presence of skimmed milk, namely, B. licheniformis, Geobacillus stearothermophilus, Geobacillus thermoleovorans group and Anoxybacillus flavithermus. The maximum number of cells recovered from the biofilms developed on SS coupons in the presence of skimmed milk for these four species was as follows: 4.8, 5.2, 4.5 and 5.3logCFU/cm, respectively. Number of cells recovered from biofilms on 1cm SS coupons increased in the presence of tryptic soy broth (TSB) for all mesophiles including B. licheniformis, while decreased for G. stearothermophilus, G. thermoleovorans group and A. flavithermus. The crystal violet staining assay on polystyrene proved to be inadequate to predict cell counts on SS for the bacteria tested in our trial in the presence of either TSB or skimmed milk. The results support the idea that biofilm formation is an important part of bacterial survival strategy as only the most prevalent isolates from milk powders formed good biofilms on SS in the presence of skimmed milk. Biofilm formation also proved to be a strain-dependent characteristic and interestingly significant variation in biofilm formation was observed within the same RAPD groups of B. licheniformis which supports the previously reported genetic and phenotypic heterogeneity within the same RAPD based groups. The work reported in this manuscript will broaden our knowledge on biofilm formation of a large number of dairy isolates and emphasize strain and substrate dependence.
乳制品生产工厂表面的生物膜是微生物污染的潜在储存库。这些微生物聚集体可能含有污染乳制品的致病和腐败微生物。许多源自乳制品的产芽孢分离株的生物膜形成能力尚未得到足够关注。本研究探讨了148株嗜温菌和嗜热菌分离株的生物膜形成潜力，特别强调了地衣芽孢杆菌在聚苯乙烯和不锈钢（SS）表面的情况。我们得出结论，在脱脂牛奶存在的情况下，只有四种菌对SS表面生物膜的形成具有重要意义，即地衣芽孢杆菌、嗜热栖热放线菌、嗜热栖热嗜热栖热菌组和嗜热栖热嗜热栖热菌。在脱脂牛奶存在的情况下，从SS试片上形成的生物膜中回收的这四种菌的最大细胞数分别如下：4.8、5.2、4.5和5.3logCFU/cm。在胰蛋白胨大豆肉汤（TSB）存在的情况下，包括地衣芽孢杆菌在内的所有嗜温菌从1cm SS试片上的生物膜中回收的细胞数增加，而嗜热栖热放线菌、嗜热栖热嗜热栖热菌组和嗜热栖热嗜热栖热菌的细胞数减少。在我们的试验中，无论是在TSB还是脱脂牛奶存在的情况下，聚苯乙烯上的结晶紫染色试验都不足以预测所测试细菌在SS上的细胞数。结果支持了生物膜形成是细菌生存策略重要组成部分的观点，因为只有奶粉中最常见的分离株在脱脂牛奶存在的情况下能在SS上形成良好的生物膜。生物膜形成也被证明是一种菌株依赖性特征，有趣的是，在地衣芽孢杆菌的同一随机扩增多态性DNA（RAPD）组内观察到生物膜形成的显著差异，这支持了先前报道的基于RAPD的同一组内的遗传和表型异质性。本手稿中报道的工作将拓宽我们对大量乳制品分离株生物膜形成的认识，并强调菌株和底物依赖性。
