一株牛源都柏林沙门氏菌的全基因组测序及毒力与耐药性分析

Whole-genome sequencing, virulence, and drug resistance of a bovine-derived strain of Salmonella enterica subsp. enterica serovar Dublin

摘要:

【背景】沙门氏菌(Salmonella spp.)是重要的人畜共患病原菌，其毒力和耐药性的不断增强引起广泛关注。【目的】了解从通辽市一犊牛死亡病例中所分离牛源都柏林沙门氏菌的毒力及耐药性情况。【方法】以病死犊牛肺脏为材料，经细菌分离纯化及16S rRNA基因测序，鉴定病原为沙门氏菌。采用动物试验、药敏试验和PCR方法对分离菌进行毒力、耐药性，以及毒力基因和耐药基因检测，并对其进行全基因组测序分析。【结果】分离菌具有较强毒力，对小鼠半数致死量为2.8×10⁶ CFU/mL。分离菌为多重耐药菌，仅对多粘菌素B和噻孢霉素敏感，对强力霉素和恩诺沙星中度敏感。检测13种沙门氏菌常见毒力基因，检出率为92.3%。对分离菌进行全基因组测序分析，该菌株为都柏林沙门氏菌，基因组大小为4 965 370 bp，GC含量为52.12%，同时携带2个质粒，大小分别为79 524 bp (pTLS-1)和45 301 bp (pTLS-2)。分离菌中共携带996个毒力基因和24个毒力岛；共携带42个耐药基因，其中4个为可水平转移基因，基因组中存在9个可移动遗传元件，包括插入序列和转座子等。【结论】分离牛源都柏林沙门氏菌菌株具有较强毒力且为多重耐药株，携带大量毒力基因及耐药基因。

Abstract:

[Background] The virulence and drug resistance of Salmonella spp. as a major zoonotic pathogen have attracted widespread attention. [Objective] To investigate the virulence and drug resistance of Salmonella enterica subsp. enterica serovar Dublin isolated from a dead calf in Tongliao City. [Methods] Bacterial isolation and 16S rRNA gene sequencing were performed with the lung of a dead calf, and the pathogen was identified as Salmonella. Animal tests, drug sensitivity tests, and PCR were employed to examine the virulence gene, drug resistance, virulence, and drug resistance genes of the isolate, and the whole genome was sequenced. [Results] The isolate had strong virulence, with the median lethal dose of 2.8×10⁶ CFU/mL to mice. It was multidrug-resistant, sensitive to only polymyxin B and cephalothin, and moderately sensitive to doxycycline and enrofloxacin. The detection rate of 13 virulence genes was 92.3%. The whole genome of the isolate had the length of 4 965 370 bp and the GC content of 52.12%, and it carried two plasmids with the lengths of 79 524 bp (pTLS-1) and 45 301 bp (pTLS-2), respectively. The isolate carried 996 virulence genes and 24 pathogenicity islands. A total of 42 drug-resistant genes were detected, among which 4 were horizontal transferable genes. In addition, there were 9 mobile genetic elements in the genome, including insertion sequences, transposons, etc. [Conclusion] The Salmonella Dublin strain isolated from a calf was virulent and multidrug-resistant, carrying a large number of virulence genes and drug-resistant genes.