探究一株新现食源性多重耐药非典型肠致病大肠杆菌（aEPEC）表型、生化及遗传特征。从市售食品中分离到一株产ESBL且携带质粒介导多粘菌耐药基因mcr-1的aEPEC菌株E2892A1，利用API 20E对其生化特征进行了分析，采用微量肉汤稀释法测定了常见抗生素MICs，通过基因组测序分析了遗传特征（耐药基因、质粒类型、毒力基因），并基于cgSNP对其遗传进化关系进行了探究。结果表明，该菌株对多种常用抗生素如头孢他定，头孢曲松，四环素、氨苄西林等耐药，且属于ESBL菌株。测序结果显示，该菌株为aEPEC，其携带17种耐药基因和EPEC特征毒力基因eae，具有4种复制子类型。这是国内外首次发现多种耐药基因（特别是CTX-123和mcr-1）共存于同一株多重耐药aEPEC ST752菌株中。接合实验证实mcr-1基因可水平传播至大肠杆菌C600。这类菌株存在于食品中对人体健康构成了重要威胁，需特别关注其扩散情况。该研究为食品中高毒力多重耐药菌风险监测提供了重要基础数据，可为畜牧养殖中抗生素合理使用和食源性疾病用药方案制定提供数据参考。

The phenotypic, biochemical, and genetic characteristics of an emerging food-borne multidrug-resistant atypical enteropathogenic Escherichia coli (aEPEC) strain were explored. An extended-spectrum β-lactamase (ESBL)-producing atypical aEPEC strain, E2892A1, carrying the plasmid-mediated colistin resistance gene mcr-1 was isolated from retail food. The biochemical characteristics were analyzed using the Analytical Profile Index 20E test. The minimal inhibitory concentrations of antibiotics were determined using the microbroth dilution method. Further, the genetic characteristics (antibiotic resistance genes, plasmid replicon types, and virulence genes) were analyzed using whole-genome sequencing (WGS), and the genetic evolutionary relationship was constructed based on core genome single nucleotide polymorphism cluster analysis. The results indicated that the aEPEC E2892A1 strain had a high prevalence of resistance to ceftazidine, ceftriaxone, tetracycline, ampicillin, and other commonly used antibiotics and was an ESBL-producing strain. WGS results showed that the strain was an aEPEC and carried 17 antibiotic-resistance genes, the virulence gene eae, and four plasmid replicon subtypes. This is the first report of multiple resistance genes (especially CTX-123 and mcr-1) co-existing in the same ESBL-producing aEPEC ST752 strain. Conjugation experiments confirmed that the mcr-1 gene could be transmitted horizontally to E. coli C600. The presence of such a strain in food poses a potential health threat to humans. Thus, continuous attention to its spread is essential. This study provides important basic data for monitoring the risk of highly virulent multidrug-resistant bacteria in food, which can aid the rational use of antibiotics and the formulation of clinical protocols for the treatment of food-borne diseases.

国家自然科学基金项目（32072325）；广东省基础与应用基础研究基金（2023A1515011848）；广东省科学院创新发展专项（2020GDASYL-20200103024）