该研究采用纸片扩散法对生鲜食品源沙门氏菌分离株进行耐药表型检测，玻片凝集法测定血清型，MLST方法分析其序列型。用PCR检测结合序列比对，对多重耐药沙门氏菌携带的Ⅰ类整合子及其基因盒、ISCR1及其基因盒进行分析。共筛选出32株多重耐药菌株，多重耐药率为48.48%。多重耐药株中分为11种血清型，优势血清型为S. Thompson（21.88%）和S. Agona（18.75%），MLST的序列分型将多重耐药株分为15种ST型，优势序列型为ST26（21.88%）和ST13（12.50%）。多重耐药菌株中，Ⅰ类整合子的检出率为43.75%（14/32），其中有5株扩出耐药基因盒，检出率为35.71%（5/14）；11株检出ISCR1序列，检出率为34.38%（11/32），其中4株扩增出耐药基因盒，检出率为36.36%（4/11）；同时含有这两种遗传元件（Ⅰ型复合整合子）的菌株共检测出9株，检出率为28.13%（9/32），检出的基因盒大多包含1~2种耐药基因，与耐药表型具有较好的相关性。通过blast比对，发现28号菌株中的Ⅰ型复合整合子耐药基因盒与沙门氏菌Nsa217质粒和肺炎克雷伯菌的KP15-2-53质粒具有同源性。生鲜制品中沙门氏菌耐药性相对严重，且沙门氏菌多重耐药性与携带的Ⅰ型复合整合子之间具有相关性。

Salmonella isolates from fresh food were subjected to resistant phenotype testing using the disk diffusion method, serotyping via slide agglutination, and sequence type analysis via the multilocus sequence typing (MLST) method. Class I integrons, ISCR1, and their gene cassettes in multidrug-resistant Salmonella were analyzed via PCR and sequence alignment. A total of 32 multidrug-resistant strains were detected, and the multidrug resistance rate among all strains was 48.48%. The multidrug-resistant strains were divided into 11 serotypes, with S. Thompson (21.88%) and S. Agona (18.75%) being the dominant serotypes. Using the MLST method, the multidrug-resistant strains were divided into 15 sequence types (STs), with the dominant STs being ST26 (21.88%) and ST13 (12.50%). Among the multidrug-resistant strains, the detection rate of class I integrons was 43.75% (14/32), with drug resistance gene cassettes amplified in five isolates (5/14, detection rate: 35.71%); the detection rate of ISCR1 was 34.38%, (11/32), with drug resistance gene cassettes amplified in four isolates (4/11, detection rate: 36.36%). Both genetic elements (complex class I integron and ISCR1) were present in nine strains (9/32, detection rate: 28.13%). The majority of detected gene cassettes contained one or two drug resistance genes, which correlated well with the resistant phenotypes. Through sequence comparison using BLAST, it was found that the resistance gene cassette of the class I integron in Strain No. 28 was homologous to the Nsa217 plasmid of Salmonella and the KP15-2-53 plasmid of Klebsiella pneumoniae. Our results indicate that the drug resistance of Salmonella in fresh food products is relatively strong, and that multidrug resistance in Salmonella is related to the complex class I integrons harbored by the strains.

国家重点研发计划重点专项（2016YFD0401202）