Wu Shi, Wu Qingping, Zhang Jumei, Chen Moutong, Guo Weipeng
Guangdong Institute of Microbiology, State Key Laboratory of Applied Microbiology Southern China, Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Open Laboratory of Applied MicrobiologyGuangzhou, China; School of Bioscience and Bioengineering, South China University of TechnologyGuangzhou, China.
Guangdong Institute of Microbiology, State Key Laboratory of Applied Microbiology Southern China, Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Open Laboratory of Applied Microbiology Guangzhou, China.
Front Microbiol. 2016 Feb 16;7:168. doi: 10.3389/fmicb.2016.00168. eCollection 2016.
Eighty Listeria monocytogenes isolates were obtained from Chinese retail ready-to-eat (RTE) food and were previously characterized with serotyping and antibiotic susceptibility tests. The aim of this study was to characterize the subtype and virulence potential of these L. monocytogenes isolates by multilocus sequence typing (MLST), virulence-associate genes, epidemic clones (ECs), and sequence analysis of the important virulence factor: internalin A (inlA). The result of MLST revealed that these L. monocytogenes isolates belonged to 14 different sequence types (STs). With the exception of four new STs (ST804, ST805, ST806, and ST807), all other STs observed in this study have been associated with human listeriosis and outbreaks to varying extents. Six virulence-associate genes (inlA, inlB, inlC, inlJ, hly, and llsX) were selected and their presence was investigated using PCR. All strains carried inlA, inlB, inlC, inlJ, and hly, whereas 38.8% (31/80) of strains harbored the listeriolysin S genes (llsX). A multiplex PCR assay was used to evaluate the presence of markers specific to epidemic clones of L. monocytogenes and identified 26.3% (21/80) of ECI in the 4b-4d-4e strains. Further study of inlA sequencing revealed that most strains contained the full-length InlA required for host cell invasion, whereas three mutations lead to premature stop codons (PMSC) within a novel PMSCs at position 326 (GAA → TAA). MLST and inlA sequence analysis results were concordant, and different virulence potentials within isolates were observed. These findings suggest that L. monocytogenes isolates from RTE food in China could be virulent and be capable of causing human illness. Furthermore, the STs and virulence profiles of L. monocytogenes isolates have significant implications for epidemiological and public health studies of this pathogen.
从中国零售即食（RTE）食品中获取了80株单核细胞增生李斯特菌分离株，之前已通过血清分型和抗生素敏感性试验对其进行了表征。本研究的目的是通过多位点序列分型（MLST）、毒力相关基因、流行克隆（ECs）以及重要毒力因子内化素A（inlA）的序列分析，来表征这些单核细胞增生李斯特菌分离株的亚型和毒力潜力。MLST结果显示，这些单核细胞增生李斯特菌分离株属于14种不同的序列类型（STs）。除了4种新的STs（ST804、ST805、ST806和ST807）外，本研究中观察到的所有其他STs在不同程度上都与人类李斯特菌病和疫情爆发有关。选择了6个毒力相关基因（inlA、inlB、inlC、inlJ、hly和llsX），并使用PCR检测它们的存在情况。所有菌株都携带inlA、inlB、inlC、inlJ和hly，而38.8%（31/80）的菌株含有李斯特菌溶血素S基因（llsX）。使用多重PCR检测法评估单核细胞增生李斯特菌流行克隆特异性标志物的存在情况，在4b - 4d - 4e菌株中鉴定出26.3%（21/80）的ECI。对inlA测序的进一步研究表明，大多数菌株含有宿主细胞入侵所需的全长InlA，而三个突变导致在第326位（GAA → TAA）出现一个新的提前终止密码子（PMSC）。MLST和inlA序列分析结果一致，并且在分离株中观察到了不同的毒力潜力。这些发现表明，中国RTE食品中的单核细胞增生李斯特菌分离株可能具有毒性，能够导致人类疾病。此外，单核细胞增生李斯特菌分离株的STs和毒力谱对该病原体的流行病学和公共卫生研究具有重要意义。
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