Radmehr Behrad, Zaferanloo Bita, Tran Thien, Beale David J, Palombo Enzo A
Department of Chemistry and Biotechnology, Swinburne University of Technology, Hawthorn, VIC, 3122, Australia.
Bruker Pty Ltd, Preston, VIC, 3072, Australia.
Curr Microbiol. 2020 Oct;77(10):3065-3075. doi: 10.1007/s00284-020-02129-6. Epub 2020 Jul 21.
The elimination of spore-forming bacteria is not guaranteed by current pasteurisation processes and is a challenging problem for the dairy industry. Given that Bacillus cereus sensu lato (B. cereus group) is an important foodborne pathogen and spoiler in the dairy industry, this study aimed at evaluating the prevalence and characteristics of B. cereus group in raw and pasteurised milk samples collected in Victoria, Australia. Isolated B. cereus group were tested for antimicrobial susceptibility, biofilm formation and virulence properties. Genetic diversity was assessed using ERIC-PCR. Proteomic profiling using MALDI-TOF MS and chemical profiling using Fourier-transform infrared (FTIR) spectroscopy were also applied for clustering of the isolates. Results showed 42.3% of milk samples contained B. cereus group, with a higher contamination level for pasteurised milk. Virulence studies identified genes nheA, nheB, hblA and nheC in most isolates and cyk gene in 46% of all isolates. Antimicrobial susceptibility testing showed a high prevalence of resistance towards ampicillin, ceftriaxone and penicillin. The biofilm-forming capacity of our isolates showed that most (53.7%) had the ability to form a biofilm. Genetic profiling using ERIC-PCR placed most B. cereus group isolates from pasteurised milk in the same cluster, indicating that they probably originated from a similar source. Raw milk isolates showed greater diversity indicating various sources. FTIR spectroscopy showed high agreement with genetic profiling. In contrast, low agreement between proteomic (MALDI-TOF MS) and genetic typing was observed. The present study showed that the FTIR spectroscopy could be adopted as a rapid tool for the typing of B. cereus group. Overall, the virulence and antimicrobial resistance characteristics, together with the ability of isolates to produce biofilm, indicate the importance of B. cereus group in the Australian dairy industry.
目前的巴氏杀菌工艺无法保证杀灭形成芽孢的细菌，这对乳制品行业来说是一个具有挑战性的问题。鉴于蜡样芽孢杆菌复合群（蜡样芽孢杆菌属）是乳制品行业中一种重要的食源性病原体和腐败菌，本研究旨在评估在澳大利亚维多利亚州采集的生乳和巴氏杀菌乳样品中蜡样芽孢杆菌复合群的流行情况和特征。对分离出的蜡样芽孢杆菌复合群进行了药敏试验、生物膜形成试验和毒力特性检测。采用ERIC-PCR评估基因多样性。还应用基质辅助激光解吸电离飞行时间质谱（MALDI-TOF MS）进行蛋白质组分析以及傅里叶变换红外（FTIR）光谱进行化学分析，以对分离株进行聚类。结果显示，42.3%的牛奶样品含有蜡样芽孢杆菌复合群，巴氏杀菌乳的污染水平更高。毒力研究在大多数分离株中鉴定出nheA、nheB、hblA和nheC基因，在所有分离株的46%中鉴定出cyk基因。药敏试验表明，对氨苄西林、头孢曲松和青霉素耐药的情况很普遍。我们分离株的生物膜形成能力表明，大多数（53.7%）具有形成生物膜的能力。使用ERIC-PCR进行基因分型显示，大多数来自巴氏杀菌乳的蜡样芽孢杆菌复合群分离株聚在同一簇中，表明它们可能来自相似的来源。生乳分离株显示出更大的多样性，表明来源各异。FTIR光谱与基因分型结果高度一致。相比之下，观察到蛋白质组学（MALDI-TOF MS）与基因分型之间的一致性较低。本研究表明，FTIR光谱可作为蜡样芽孢杆菌复合群分型的快速工具。总体而言，毒力和耐药特性以及分离株产生生物膜的能力表明蜡样芽孢杆菌复合群在澳大利亚乳制品行业中的重要性。
