Department of Genomic Sciences, North Carolina State University, Raleigh, North Carolina, USA.
Appl Environ Microbiol. 2012 Oct;78(19):6938-45. doi: 10.1128/AEM.01553-12. Epub 2012 Jul 27.
The persistence of Listeria monocytogenes in food processing plants and other ecosystems reflects its ability to adapt to numerous stresses. In this study, we investigated 138 isolates from foods and food processing plants for resistance to the quaternary ammonium disinfectant benzalkonium chloride (BC) and to heavy metals (cadmium and arsenic). We also determined the prevalence of distinct cadmium resistance determinants (cadA1, cadA2, and cadA3) among cadmium-resistant isolates. Most BC-resistant isolates were resistant to cadmium as well. Arsenic resistance was encountered primarily in serotype 4b and was an attribute of most isolates of the serotype 4b epidemic clonal group ECIa. Prevalence of the known cadmium resistance determinants was serotype associated: cadA1 was more common in isolates of serotypes 1/2a and 1/2b than 4b, while cadA2 was more common in those of serotype 4b. A subset (15/77 [19%]) of the cadmium-resistant isolates lacked the known cadmium resistance determinants. Most of these isolates were of serotype 4b and were also resistant to arsenic, suggesting novel determinants that may confer resistance to both cadmium and arsenic in these serotype 4b strains. The findings may reflect previously unrecognized components of the ecological history of different serotypes and clonal groups of L. monocytogenes, including exposures to heavy metals and disinfectants.
单核细胞增生李斯特菌在食品加工厂和其他生态系统中的持续存在反映了其适应众多压力的能力。在本研究中，我们调查了来自食品和食品加工厂的 138 株分离物对季铵消毒剂苯扎氯铵（BC）和重金属（镉和砷）的抗性。我们还确定了耐镉分离物中不同镉抗性决定因素（cadA1、cadA2 和 cadA3）的流行情况。大多数 BC 抗性分离物也对镉具有抗性。砷抗性主要在血清型 4b 中遇到，并且是血清型 4b 流行克隆群 ECIa 的大多数分离物的特征。已知镉抗性决定因素的流行情况与血清型有关：cadA1 在血清型 1/2a 和 1/2b 的分离物中比 4b 更常见，而 cadA2 在 4b 血清型中更常见。一组（15/77 [19%]）耐镉的分离物缺乏已知的镉抗性决定因素。这些分离物中的大多数为血清型 4b，并且对砷也具有抗性，表明在这些血清型 4b 菌株中可能具有同时赋予对镉和砷抗性的新决定因素。这些发现可能反映了不同血清型和单核细胞增生李斯特菌克隆群的生态历史中以前未被认识到的组成部分，包括对重金属和消毒剂的暴露。
