Heterogeneity, Characteristics, and Public Health Implications of Listeria monocytogenes in Ready-to-Eat Foods and Pasteurized Milk in China
Heterogeneity, Characteristics, and Public Health Implications of Listeria monocytogenes in Ready-to-Eat Foods and Pasteurized Milk in China
复制标题
中国即食食品和巴氏杀菌奶中单增李斯特菌的异质性、特征和公共卫生影响
DOI：
10.3389/fmicb.2020.00642
复制
发表时间：
2020-04-15
影响因子：
5.2
通讯作者：
Kou Xiuying
中科院分区：
文献类型：
--
作者：
Chen Yuetao;Chen Moutong;Kou Xiuying
单核细胞增生李斯特菌是一种食源性致病菌，在人类中具有高死亡率。本研究的目的是确定L.根据表型和基因型特征，对中国即食食品和巴氏杀菌乳中分离的单核细胞增多症进行了研究。约7.7%（44/570）的样本检测为L阳性。在10.8%（39/360）的RTE和2.4%（5/210）的巴氏杀菌乳样品中，单核细胞增多症的检出率分别为77.3%（34/44）< 10 MPN/g、18.2%（8/44）10-110 MPN/g和4.5%（2/44）> 110 MPN/g。共检测到48株L.从44例阳性标本中分离出单核细胞增多症。PCR-血清型分析显示，最流行的血清型为II. 2其次为I.1（1/2a-3a）占33.3%（16/48），I.2（1/2c-3c）占12.5%（6/48），Ⅱ.1群（4 b-4d-4 e）占2.1%。通过多位点序列分型，将所有分离株分为11个序列型（ST），分别属于10个克隆复合体（CC）和1个单克隆（ST 619）。最常见的ST是ST 87（29.2%），其次是ST 8（22.9%）和ST 9（12.5%）。毒力基因测定结果表明，所有分离株均携带8个毒力基因，分别属于李斯特菌致病岛1（LIPI-1）（prfA、actA、hly、mpl、plcA、plcB和iap）和inlB。大约85.4%的菌株携带全长inlA，而7个菌株在inlA中具有提前终止密码子，其中6个属于ST 9，1个属于ST 5。此外，LLS（由llsX基因编码，代表LIPI-3）在感染期间显示杀菌活性并修饰宿主微生物群。LIPI-4增强了L.单核细胞增多症结果表明，6株（12.5%）分离株携带llsX基因，分别属于ST 1/CC 1、ST 3/CC 3和ST 619。约31.3%（15/48）的分离株（属于ST 87/CC 87和ST 619）携带ptsA（代表LIPI-4），表明该病原体的潜在风险。药敏试验显示，> 95%的分离株对16种抗菌药物敏感，但对链霉素和环丙沙星的耐药率分别为60.4%和22.9%。结果表明，部分分离株携带LIPI-3和LIPI-4基因，这可能是李斯特菌在消费者中感染的一种可能的传播途径。
Listeria monocytogenes is a foodborne pathogen with a high mortality rate in humans. This study aimed to identify the pathogenic potential of L. monocytogenes isolated from ready-to-eat (RTE) foods and pasteurized milk in China on the basis of its phenotypic and genotypic characteristics. Approximately 7.7% (44/570) samples tested positive for L. monocytogenes among 10.8% (39/360) RTE and 2.4% (5/210) pasteurized milk samples, of which 77.3% (34/44) had < 10 MPN/g, 18.2% (8/44) had 10–110 MPN/g, and 4.5% (2/44) had > 110 MPN/g. A total of 48 strains (43 from RTE foods and five from milk samples) of L. monocytogenes were isolated from 44 positive samples. PCR-serogroup analysis revealed that the most prevalent serogroup was II.2 (1/2b-3b-7), accounting for 52.1% (25/48) of the total, followed by serogroup I.1 (1/2a-3a) accounting for 33.3% (16/48), serogroup I.2 (1/2c-3c) accounting for 12.5% (6/48), and serogroup II.1 (4b-4d-4e) accounting for 2.1%. All isolates were grouped into 11 sequence types (STs) belonging to 10 clonal complexes (CCs) and one singleton (ST619) via multi-locus sequence typing. The most prevalent ST was ST87 (29.2%), followed by ST8 (22.9%), and ST9 (12.5%). Virulence genes determination showed that all isolates harbored eight virulence genes belonging to Listeria pathogenicity islands 1 (LIPI-1) (prfA, actA, hly, mpl, plcA, plcB, and iap) and inlB. Approximately 85.4% isolates carried full-length inlA, whereas seven isolates had premature stop codons in inlA, six of which belonged to ST9 and one to ST5. Furthermore, LLS (encoded by llsX gene, representing LIPI-3) displays bactericidal activity and modifies the host microbiota during infection. LIPI-4 enhances neural and placental tropisms of L. monocytogenes. Results showed that six (12.5%) isolates harbored the llsX gene, and they belonged to ST1/CC1, ST3/CC3, and ST619. Approximately 31.3% (15/48) isolates (belonging to ST87/CC87 and ST619) harbored ptsA (representing LIPI-4), indicating the potential risk of this pathogen. Antimicrobial susceptibility tests revealed that > 95% isolates were susceptible to 16 antimicrobials; however, 60.4 and 22.9% isolates were intermediately resistant to streptomycin and ciprofloxacin, respectively. The results show that several isolates harbor LIPI-3 and LIPI-4 genes, which may be a possible transmission route for Listeria infections in consumers.