Jiangsu Key Laboratory for Food Quality and Safety-State Key Laboratory Cultivation Base of MOST, Institute of Food Safety and Nutrition, Jiangsu Academy of Agricultural Sciences, No 50 Zhongling Street, Nanjing, 210014, Jiangsu, China.
College of Food Science and Engineering, Yangzhou University, Yangzhou, 225009, China.
BMC Microbiol. 2021 Nov 25;21(1):327. doi: 10.1186/s12866-021-02335-7.
Listeria monocytogenes is one of the deadliest foodborne pathogens. The bacterium can tolerate severe environments through biofilm formation and antimicrobial resistance. This study aimed to investigate the antimicrobial susceptibility, resistance genes, virulence, and molecular epidemiology about Listeria from meat processing environments.
This study evaluated the antibiotic resistance and virulence of Listeria isolates from slaughtering and processing plants. All isolates were subjected to antimicrobial susceptibility testing using a standard microbroth dilution method. The harboring of resistant genes was identified by polymerase chain reaction. The multilocus sequence typing was used to determine the subtyping of the isolates and characterize possible routes of contamination from meat processing environments. The virulence of different STs of L. monocytogenes isolates was evaluated using a Caco-2 cell invasion assay.
A total of 59 Listeria isolates were identified from 320 samples, including 37 L. monocytogenes isolates (62.71%). This study evaluated the virulence of L. monocytogenes and the antibiotic resistance of Listeria isolates from slaughtering and processing plants. The susceptibility of these 59 isolates against 8 antibiotics was analyzed, and the resistance levels to ceftazidime, ciprofloxacin, and lincomycin were as high as 98.31% (L. m 37; L. innocua 7; L. welshimeri 14), 96.61% (L. m 36; L. innocua 7; L. welshimeri 14), and 93.22% (L. m 35; L. innocua 7; L. welshimeri 13), respectively. More than 90% of the isolates were resistant to three to six antibiotics, indicating that Listeria isolated from meat processing environments had high antimicrobial resistance. Up to 60% of the isolates harbored the tetracycline-resistance genes tetA and tetM. The frequency of ermA, ermB, ermC, and aac(6')-Ib was 16.95, 13.56, 15.25, and 6.78%, respectively. Notably, the resistant phenotype and genotype did not match exactly, suggesting that the mechanisms of antibiotic resistance of these isolates were likely related to the processing environment. Multilocus sequence typing (MLST) revealed that 59 Listeria isolates were grouped into 10 sequence types (STs). The dominant L. monocytogenes STs were ST5, ST9, and ST121 in the slaughtering and processing plant of Jiangsu province. Moreover, ST5 subtypes exhibited high invasion in Caco-2 cells compared with ST9 and ST121 cells.
The dominant L. monocytogenes ST5 persisted in the slaughtering and processing plant and had high antimicrobial resistance and invasion characteristics, illustrating a potential risk in food safety and human health.
李斯特菌是最致命的食源性病原体之一。该细菌可以通过生物膜形成和抗微生物耐药性来耐受恶劣环境。本研究旨在调查来自肉类加工环境的李斯特菌的抗菌药物敏感性、耐药基因、毒力和分子流行病学情况。
本研究评估了屠宰和加工厂中李斯特菌分离株的抗生素耐药性和毒力。所有分离株均采用标准微量肉汤稀释法进行抗菌药物敏感性试验。通过聚合酶链反应鉴定耐药基因的存在。多位点序列分型用于确定分离株的亚型，并从肉类加工环境中确定可能的污染途径。使用 Caco-2 细胞侵袭试验评估不同 ST 李斯特菌分离株的毒力。
从 320 个样本中鉴定出 59 株李斯特菌，其中 37 株为单核细胞增生李斯特菌（62.71%）。本研究评估了屠宰和加工厂中李斯特菌分离株的毒力和抗生素耐药性。分析了这些 59 株分离株对 8 种抗生素的敏感性，发现这些分离株对头孢他啶、环丙沙星和林可霉素的耐药率分别高达 98.31%（L. m 37；L. innocua 7；L. welshimeri 14）、96.61%（L. m 36；L. innocua 7；L. welshimeri 14）和 93.22%（L. m 35；L. innocua 7；L. welshimeri 13）。超过 90%的分离株对三种至六种抗生素具有耐药性，表明从肉类加工环境中分离出的李斯特菌具有很高的抗微生物耐药性。多达 60%的分离株携带四环素耐药基因 tetA 和 tetM。ermA、ermB、ermC 和 aac(6')-Ib 的检出率分别为 16.95%、13.56%、15.25%和 6.78%。值得注意的是，耐药表型和基因型并不完全匹配，表明这些分离株的抗生素耐药机制可能与加工环境有关。多位点序列分型（MLST）显示，59 株李斯特菌分为 10 种序列型（ST）。在江苏省的屠宰和加工场，优势单核细胞增生李斯特菌 ST 型为 ST5、ST9 和 ST121。此外，ST5 亚型在 Caco-2 细胞中的侵袭能力明显高于 ST9 和 ST121 细胞。
优势单核细胞增生李斯特菌 ST5 持续存在于屠宰和加工场，具有较高的抗微生物耐药性和侵袭特性，说明其对食品安全和人类健康存在潜在风险。
