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

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

doi:10.3389/fmicb.2019.01710

Yunyi Zhang, Jiancai Chen + Show 8 more

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https://doi.org/10.3389/fmicb.2019.01710

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Abstract

Listeria monocytogenes is an important foodborne pathogen causing public concern. A total of 3354 retail foods in bulk were sampled and screened for L. monocytogenes. Seventy-three (2.2%) samples including 21 ready-to-eat (RTE) foods and 52 raw foods were confirmed positive for L. monocytogenes. 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, L. monocytogenes 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, L. monocytogenes was not detected in raw freshwater food. The L. monocytogenes 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 L. monocytogenes 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 Listeria pathogenicity islands (LIPI) in L. monocytogenes isolates. prfA, hly, plcA, plcB, mpl, actA genes in LIPI-1 and inlA, inlB, inlC, inlJ genes in LIPI-2 were detected in approximately all L. monocytogenes 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 L. monocytogenes in foods, assess the potential risk of this pathogen and further address the safety issue of retail foods in bulk in China.

Highlights

Listeria monocytogenes is an important foodborne pathogen which can cause severe human listeriosis, in older adults, newborns, pregnant women and immunecompromised individuals, resulting in septicemia, abortion, preterm delivery, stillbirth, meningitis, encephalomyelitis, or even death (Lomonaco et al, 2009; Lamont et al, 2011)
L. monocytogenes was isolated in five RTE food categories including sushi, salmon sashimi, salad, vegetables in sauce and cooked meat
A comprehensive study of prevalence and characteristics of L. monocytogenes isolated from retail foods in bulk in Zhejiang Province, China was performed

Summary

Introduction

Listeria monocytogenes is an important foodborne pathogen which can cause severe human listeriosis, in older adults, newborns, pregnant women and immunecompromised individuals, resulting in septicemia, abortion, preterm delivery, stillbirth, meningitis, encephalomyelitis, or even death (Lomonaco et al, 2009; Lamont et al, 2011). In some cases, this bacterium’s capability to infect the central nervous system (CNS) of immunocompetent adults was revealed (Guo and Liang, 2014; Giménez-Muñoz et al, 2015). 4% of hospitalization and 19% of deaths were caused by L. monocytogenes infection (Scallan et al, 2011)

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