林麝缓慢葡萄球菌和大肠杆菌混合感染的病原分离鉴定及致病性

Isolation, identification, and pathogenicity of mixed infection of Staphylococcus lentus and Escherichia coli in Moschus berezovskii

摘要:

【背景】 林麝是我国特殊经济动物，细菌性疾病在圈养麝种群中高发，研究相关病原对林麝疾病防控具有重要意义。【目的】 探究导致1例林麝死亡的病原微生物的耐药性和致病性。【方法】 对死亡林麝进行细菌分离鉴定、药敏试验、小鼠致病性试验、耐药基因及毒力基因检测。【结果】 该林麝为缓慢葡萄球菌(Staphylococcus lentus)和大肠杆菌(Escherichia coli)混合感染，两株分离菌分别命名为菌株23HYSL和菌株23HYEC。药敏试验显示菌株23HYSL对氨曲南、林可霉素、四环素和磺胺异噁唑耐药，而菌株23HYEC为产超广谱β-内酰胺酶的多重耐药大肠杆菌。小鼠致病性试验显示菌株23HYSL的LD₅₀为1.39×10⁸ CFU，菌株23HYEC的LD₅₀为8.97×10⁷ CFU，病理切片结果显示混合感染组的脾脏病变程度更严重，并且混合感染能帮助菌株23HYEC在小鼠的心脏和肝脏定殖。两种菌均检出耐药基因sul2、tetA、tetC、bla_TEM和bla_CTX-M。同时检出菌株23HYSL携带毒力基因clfa，菌株23HYEC携带包括astA在内的5个毒力基因。【结论】 分离到林麝源缓慢葡萄球菌，同时进行了该菌与混合感染的astA⁺大肠杆菌的耐药性和致病性研究，为相关疾病的防治和合理用药提供了依据。

Abstract:

[Background] Forest musk deer are valuable economic animals in China. Captive musk deer populations frequently suffer from bacterial diseases, and thus studying the related pathogens is of great significance for the prevention and control of diseases attacking forest musk deer. [Objective] To investigate the drug resistance and pathogenicity of the microorganisms causing the death of a forest musk deer. [Methods] Bacteria were isolated from a deceased musk deer and identified. The drug susceptibility, pathogenicity in mice, and resistance gene and virulence genes of the isolates were studied. [Results] The forest musk deer suffered from mixed infection of Staphylococcus lentus (named 23HYSL) and Escherichia coli (named strain 23HYEC). The strain 23HYSL was resistant to aztreonam, lincomycin, tetracycline, and sulfisoxazole, while strain 23HYEC was a multi-drug resistant E. coli strain producing extended-spectrum β-lactamases. The median lethal doses (LD₅₀) of strain 23HYSL and strain 23HYEC in mice were 1.39×108 CFU and 8.97×107 CFU, respectively. The pathological sections showed that the mixed infection caused severer spleen lesions and facilitated the colonization of strain 23HYEC in the heart and liver of mice. Both strains carried the resistance genes sul2, tetA, tetC, bla_TEM, and bla_CTX-M. In addition, strain 23HYSL carried the virulence gene clfa, while strain 23HYEC carried 5 virulence genes including astA. [Conclusion] We isolated S. lentus from forest musk deer for the first time and studied the drug resistance and pathogenicity of this bacterium in the case of mixed infection with astA⁺ E. coli, giving insights into the prevention of related diseases and the rational use of drugs.