本研究对食品样本中分离的一株多重耐药单核细胞增生李斯特菌进行耐药机制的探讨，以期对食源性单核细胞增生李斯特菌多重耐药现象的控制提供理论依据。本文通过聚合酶链式反应筛选耐药决定因子，质粒消除及自然转化实验对耐药决定因子进行定位及传播能力的探讨，最后通过传代实验验证该菌株多重耐药性传播的稳定性。结果表明，对检测到的多重耐药菌株LM78（耐受氯霉素、红霉素、链霉素、四环素、复方新诺明）进行相关耐药基因检测，检测到cat、ermB、tetS 3个耐药基因。质粒消除后MIC值下降到敏感范围，且该质粒可通过自然转化在不同菌属间传递，说明这些耐药基因存在于质粒上。该质粒在无抗生素选择压力下连续传代，仍具有较高稳定性。食源性致病菌多重耐药性有可能通过不同细菌种属间转移，进而由食物链向人类传播，对人类健康造成潜在的威胁。

The mechanism of antibiotic resistance in foodborne, multidrug-resistant (MDR) Listeria monocytogenes was investigated to develop measures to control the MDR phenomenon. Genetic factors of antibiotic-resistance were screened by polymerase chain reaction (PCR), the position and dissemination capacity of these factors were evaluated by plasmid curing and natural transformation, and the stability of drug-resistance dissemination was verified by consecutive subculture. The results showed that the MDR strain LM78 (resistant to chloramphenicol, erythromycin, streptomycin, tetracycline, trimethoprim/sulfamethoxazole) carried the cat, ermB, and tetS genes. Following plasmid curing, the minimum inhibitory concentration (MIC) was reduced to the sensitive range. Moreover, the plasmid could be transferred between species by natural transformation. Plasmid curing and transformation results suggested that these resistance genes were encoded in the plasmid. After consecutive subculture without antibiotics, these plasmids remained sufficiently stable. The MDR trait of foodborne pathogens may be transferred between bacterial species, and subsequent infection in humans via contaminated foodposes a potential threat against human health.

华南理工大学中央高校基本科研业务费专项资金资助项目（2013ZB0015）；国家自然科学基金青年基金项目（31201363）；广州市科技计划项目（11C12080718）。