牛源奇异变形杆菌的分离、鉴定及耐药性分析

Isolation,Identification and Drug Resistance Analysis of Proteus mirabilis from Dairy Cow

【目的】确定导致某牛场犊牛腹泻并死亡的原因。【方法】采集引起犊牛腹泻甚至死亡的病理样品并从中分离得到1株优势菌株,通过形态特征、生化试验、16S rRNA遗传分析、小鼠致病性试验以及药敏试验对该菌进行研究。【结果】分离菌为短杆状或长丝状的革兰氏阴性菌;除七叶苷和丙二酸盐生化试验的结果呈"+"外,其他生化特性均与奇异变形杆菌相符;16S rRNA序列与NCBI中提供奇异变形杆菌序列的同源性均达100%,表明所分离菌株为奇异变形杆菌,命名为SS-1。SS-1具有较强的致病性,腹腔注射2.9×10~9 CFU/mL菌液0.2 mL,6只攻菌SPF昆明小鼠在24 h内全部死亡,解剖见心脏积液,肺部出血明显,肝脏淤血、肿大,肠道充血、肠壁变薄、肠内积有大量黄色透明的黏液性内容物;组织病理学变化为肺出血,肝、脾和肾淤血,炎性细胞浸润等。药敏试验结果发现:SS-1的耐药性较特殊,仅对青霉素类部分抗生素如氨苄西林、氨基糖苷类部分抗生素如丁胺卡那、喹诺酮类部分抗生素如氧氟沙星和头孢菌素类部分抗生素如头孢哌酮敏感;对林可氨类、四环素类、碳青霉烯类和大环内酯类药物耐药。【结论】从腹泻病牛分离到的SS-1与以往报道的奇异变形杆菌在生化特性、药敏特性以及小鼠致病力等方面有一定差异,表明该菌可能发生变异毒力增强,是引起该牛腹泻甚至死亡的重要致病菌,应引起高度重视。

[Purpose]To determine the cause of diarrhea and death of calves in a cattle farm.[Method]A dominant strain was isolated from the pathological samples of causing diarrhea and even death of calves and analyzed by morphological characteristics,biochemical test,16S rRNA genetic analysis,mouse pathogenicity test and drug susceptibility test.[Result]The isolates were short rod-shaped or filamentous gram-negative bacteria.Except that the biochemical results of glucoside and malonate were"+",the other biochemical characteristics were consistent with that of Proteus mirabils;the 16S rRNA sequence shares 100%homology with the P.mirabilis sequence in NCBI.The results showed that the isolated strain was P.mirabilis and named SS-1.SS-1 has strong pathogenicity,intraperitoneal injection of 2.9×10~9 CFU/mL bacterial solution 0.2 mL,6 strains of SPF Kunming mice all died within 24 h,dissection showed cardiac effusion,pulmonary hemorrhage,liver congestion,swelling,intestinal congestion,thinning of the intestinal wall,and a large amount of yellow transparent mucous contents in the intestine;histopathology changes include pulmonary hemorrhage,hepatic,spleen,and kidney congestion,and inflammatory cell infiltration;drug sensitivity test results showed that SS-1 had special drug resistance,only sensitive to penicillin partial antibiotics such as ampicillin,aminoglycoside antibiotics such as amikacin,quinolones antibiotics such as ofloxacin,and cephalosporins antibiotics such as cefoperazone;it can be resistant to lincoa,tetracyclines,carbapenem and macrolides.[Conclusion]The SS-1 isolated from cows with diarrhea disease has some differences in biochemical characteristics,drug sensitivity characteristics and pathogenicity in mice from the previous reports of P.mirabilis,indicating that the bacteria may be mutated to increase the virulence,which caused the cow important pathogenic bacteria of diarrhea and even death should be highly regarded.