1株马源马红球菌的分离鉴定及耐药性与致病性分析

doi:10.16431/j.cnki.1671-7236.2024.05.041

摘要/Abstract

摘要： 【目的】马红球菌(Rhodococcus equi,R.equi)感染可导致宿主发生致命的化脓性肺炎。本研究拟对从新疆地区1例死亡马驹肺脓汁中分离获得的马红球菌临床菌株进行生物学特性分析,旨在为其临床诊疗提供指导。【方法】采集死亡马驹肺脓汁样本进行细菌分离培养。通过菌落形态观察、革兰染色、生化反应、16S rRNA PCR扩增测序鉴定菌株种属并分析其遗传进化关系;使用药敏纸片扩散法鉴定分离菌株药物敏感性;利用小鼠感染试验评估菌株致病性。【结果】分离菌株在NANAT平板上生长状态良好,菌落呈灰黑色、黏稠样,在TSA培养基上呈奶白色、黏液状,革兰染色镜检可见两头钝圆的球杆状或棒状的革兰阳性球杆菌。生化反应结果显示,分离菌株不发酵糖类,不产生靛基质、不液化明胶,氧化酶阴性,分解尿素。16S rRNA测序结果显示,分离菌株与马红球菌分离株WGC11为同一分支,亲缘关系较近。药敏试验结果显示,分离菌株对多黏菌素B及β-内酰胺类药物耐药,对其余所选抗菌药物均敏感。小鼠致病性试验结果显示,小鼠腹腔攻毒4 d内死亡率为33.3%(2/6),剩余存活小鼠剖检可见肺部出现脓肿及出血,肝脏及脾脏肿大、出血淤血;组织病理学观察可见脾脏、肝脏、肺脏组织均发生不同程度病变。【结论】本研究从新疆地区马驹肺样本中分离鉴定出1株致病性马红球菌,该菌株具有较强致病能力且存在天然耐药,试验结果为马红球菌致病机制的研究与防控奠定了理论基础。

关键词: 马红球菌; 分离鉴定; 遗传进化; 耐药性; 致病性

Abstract: 【Objective】 Rhodococcus equi infection can cause fatal suppurative pneumonia in the host.In order to provide guidance for clinical diagnosis and treatment,the biological characteristics of Rhodococcus equi isolate from lung pus of a dead foal in Xinjiang was analyzed.【Method】 The lung pus samples of dead foal were collected for bacterial isolation and culture.The species were identified by colony morphology observation,Gram staining,biochemical reaction,16S rRNA PCR amplification and sequencing,and the genetic evolution relationship was analyzed.The drug sensitivity of the isolate was determined by drug-sensitive disk diffusion method.The pathogenicity of the strain was evaluated by mouse infection test.【Result】 The isolated strain grew well on the NANAT plate,and the colonies were black and viscous,and the TSA medium was milky and slime.Blunt circles at both ends or rod-shaped Gram-positive bacilli were detected by Gram staining microscopy.The results of biochemical reaction showed that the isolated strain did not ferment carbohydrate and produce indigo matrix,did not liquefy gelatin,oxidase negative,decomposition of urea.16S rRNA sequencing results showed that the isolated strain and Rhodococcus equi strain WGC11 were in the same branch and were closely related.The results of drug sensitivity test showed that the isolated strain was resistant to polymyxin B and β-lactam drugs,and sensitive to other selected antibiotics.The results of pathogenicity test in mice showed that the mortality rate of mice was 33.3% (2/6) within 4 days of abdominal attack.Necropsy of the remaining surviving mice showed abscess and hemorrhage in lungs,swelling,bleeding and stasis of the liver and spleen.Histopathological observation showed that spleen,liver and lung tissues had different degrees of pathological changes. 【Conclusion】 A pathogenic Rhodococcus equi strain was isolated and identified from the lung samples of foal in Xinjiang.The strain had strong pathogenic ability and natural drug resistance.The results laid a theoretical foundation for the research and control of the pathogenic mechanism of Rhodococcus equi.

Key words: Rhodococcus equi; isolation and identification; genetic evolution; drug resistance; pathogenicity

中图分类号:

S855.1

段兴勋, 刘璐, 高仕文, 马玉辉, 蔡涛, 刘来珍, 顾伟芳, 赵红琼. 1株马源马红球菌的分离鉴定及耐药性与致病性分析[J]. 中国畜牧兽医, 2024, 51(5): 2210-2218.

DUAN Xingxun, LIU Lu, GAO Shiwen, MA Yuhui, CAI Tao, LIU Laizhen, GU Weifang, ZHAO Hongqiong. Isolation and Identification,Drug Resistance and Pathogenicity Analysis of A Rhodococcus equi Strain from Horse[J]. China Animal Husbandry and Veterinary Medicine, 2024, 51(5): 2210-2218.

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