AUTHOR=Zhang Yunyi , Dong Shilei , Chen Honghu , Chen Jiancai , Zhang Junyan , Zhang Zhen , Yang Yong , Xu Ziyan , Zhan Li , Mei Lingling 

TITLE=Prevalence, Genotypic Characteristics and Antibiotic Resistance of Listeria monocytogenes From Retail Foods in Bulk in Zhejiang Province, China

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.01710

DOI=10.3389/fmicb.2019.01710

ISSN=1664-302X

ABSTRACT=<p><italic>Listeria monocytogenes</italic> is an important foodborne pathogen causing public concern. A total of 3354 retail foods in bulk were sampled and screened for <italic>L. monocytogenes</italic>. Seventy-three (2.2%) samples including 21 ready-to-eat (RTE) foods and 52 raw foods were confirmed positive for <italic>L. monocytogenes</italic>. Sushi and salmon sashimi occupied the top two slots in RTE foods with relatively high presence rate of 12.9 and 6.9%, respectively. Meanwhile, <italic>L. monocytogenes</italic> was found to be distributed unequally in raw foods; the presence rates in raw meat (3.5%) and poultry (3.8%) were significantly higher than that in raw seafood (1.3%). Notably, <italic>L. monocytogenes</italic> was not detected in raw freshwater food. The <italic>L</italic>. <italic>monocytogenes</italic> isolates belonged to four serotypes, 1/2a, 1/2b, 1/2c, and 4b, with the most prevalent serotype being 1/2a (47.9%). Eighteen sequence types (STs) and eighteen virulence types (VTs) containing four newly assigned VTs (VT180, VT181, VT182, and VT183) were determined via multilocus sequence typing (MLST) and multi-virulence-locus sequence typing (MVLST). Among the 73 <italic>L. monocytogenes</italic> isolates, 23 (31.5%) belonged to epidemic clones (ECs) including ECI, ECIV, ECV, ECVI, ECVIII and ECXI among which ECV was predominant. Antibiotic susceptibility tests revealed a high resistance rate (11.0%) to tetracycline. Moreover, we identified the distribution patterns of virulence genes of four <italic>Listeria</italic> pathogenicity islands (LIPI) in <italic>L. monocytogenes</italic> isolates. <italic>prfA</italic>, <italic>hly</italic>, <italic>plcA</italic>, <italic>plcB</italic>, <italic>mpl</italic>, <italic>actA</italic> genes in LIPI-1 and <italic>inlA</italic>, <italic>inlB</italic>, <italic>inlC</italic>, <italic>inlJ</italic> genes in LIPI-2 were detected in approximately all <italic>L. monocytogenes</italic> isolates. The distribution of both LIPI-3 genes and LIPI-4 genes exhibited association with lineage and ST. LIPI-4 genes were present exclusively in ST87 isolates. Relatedness analysis revealed the absence of distinct association between STs, ECs, LIPI-3 and LIPI-4 distribution and specific food groups. This study provided fundamental data for Chinese food safety authorities to grasp the contamination status of <italic>L. monocytogenes</italic> in foods, assess the potential risk of this pathogen and further address the safety issue of retail foods in bulk in China.</p>