The New Zealand Institute for Plant & Food Research Limited, Mt Albert, Auckland, New Zealand; Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand.
Division of Pharmaceutical Biosciences, Faculty of Pharmacy, Centre for Drug Research, University of Helsinki, Helsinki, Finland.
Int J Food Microbiol. 2017 Sep 1;256:45-53. doi: 10.1016/j.ijfoodmicro.2017.05.024. Epub 2017 Jun 1.
Contamination of mussels with the human pathogen Listeria monocytogenes occurs during processing in the factory, possibly from bacteria persisting in the factory's indoor and outdoor areas. In this study, a selection of persistent (n=8) and sporadic (n=8) L. monocytogenes isolates associated with mussel-processing premises in New Zealand were investigated for their phenotypic and genomic characteristics. To identify traits that favour or contribute to bacterial persistence, biofilm formation, heat resistance, motility and recovery from dry surfaces were compared between persistent and sporadic isolates. All isolates exhibited low biofilm formation at 20°C, however, at 30°C persistent isolates showed significantly higher biofilm formation after 48h using cell enumeration and near significant difference using the crystal violet assay. All 16 isolates were motile at 20°C and 30°C and motility was fractionally higher for sporadic isolates, but no significant difference was observed. We found persistent isolates tend to exhibit greater recovery after incubation on dry surfaces compared to sporadic isolates. Two of the three most heat-resistant isolates were persistent, while four of five isolates lacking heat resistance were sporadic isolates. Comparison of genome sequences of persistent and sporadic isolates showed that there was no overall clustering of persistent or sporadic isolates, and that differences in prophages and plasmids were not associated with persistence. Our results suggest a link between persistence and biofilm formation, which is most likely multifactorial, combining subtle phenotypic and genotypic differences between isolates.
贝类受人类病原体李斯特菌污染发生在工厂加工过程中，可能是由于细菌在工厂的室内外区域持续存在。在这项研究中，选择了与新西兰贝类加工场所相关的持久性（n=8）和散发性（n=8）李斯特菌分离株，以研究其表型和基因组特征。为了确定有利于或有助于细菌持久性的特征，比较了持久性和散发性分离株的生物膜形成、耐热性、运动性和从干燥表面恢复的能力。所有分离株在 20°C 时生物膜形成能力较低，但在 30°C 时，持久性分离株在 48 小时后使用细胞计数和结晶紫测定法进行检测，生物膜形成显著增加。所有 16 个分离株在 20°C 和 30°C 时都具有运动性，且散发性分离株的运动性稍高，但未观察到显著差异。我们发现，与散发性分离株相比，持久性分离株在干燥表面上孵育后恢复的能力更强。在三种耐热性最强的分离株中，有两种是持久性的，而在缺乏耐热性的五种分离株中，有四种是散发性的。持久性和散发性分离株的基因组序列比较表明，持久性或散发性分离株没有整体聚类，而且噬菌体和质粒的差异与持久性无关。我们的结果表明，持久性与生物膜形成之间存在联系，这很可能是多因素的，结合了分离株之间细微的表型和基因型差异。
