猪源奇异变形杆菌的分离鉴定及其毒力的测定

Isolation,identification and toxicity test of Proteus mirabilis from swine

为探究引起保育猪死亡的病原菌的生物学特性、耐药性及毒力,通过形态学观察、生理生化特性测定、16S rDNA基因序列分析、药敏试验、半数致死量测定对分离菌株进行鉴定。结果表明,分离菌株为奇异变形杆菌,16S rDNA基因进化树分析表明该分离菌株与来自印度海水中的分离菌株CIFRI P-TSB-13(JF784025)的亲缘关系最近;分离菌株对头孢西丁、头孢他啶、大观霉素、氨曲南这4种抗生素高度敏感,对米诺环素、呋喃妥因、阿米卡星等10种抗生素中度敏感,对庆大霉素、氧氟沙星、左氟沙星等21种抗生素不敏感,表明分离菌株具有多重耐药性。分离菌株感染斑马鱼的半数致死量为2.12×10~5CFU/mL,感染昆明小鼠的半数致死量为1.46×10~7CFU/mL。证实引起本次保育猪细菌感染的病原为奇异变形杆菌,且该分离菌株的毒力较强,建议治疗时应针对性地选择高敏抗菌药物。

To investigate the biological characteristics,drug resistance and virulence of the pathogen which caused the death of weaned pigs,an isolate was identified through bacteria morphology,physiological and biochemical assays,the sequence analysis of 16S rDNA,drug susceptibility test and median lethal dose（LD_（50）） test.The results showed that the isolate was Proteus mirabilis.The analysis of phylogenetic tree showed that the isolate was highly similar to the P.mirabilis CIFRI P-TSB-13（JF784025） strain which was separated from Indian seawater.Drug susceptibility test indicated the isolate was highly sensitive to cefoxitin,ceftazidime,spectinomycin and aztreonam,moderately sensitive to 10 kinds of antibiotic including minocycline,amikacin and nitrofurantoin,etc.,and fully resistant to 21 kinds of antibiotic including gentamycin,ofloxacin and levofloxacin,etc.,indicating that the isolate had multi-drug resistance.When zebrafish were cloacal injected and mice were intraperitoneally injected with the strain,it had high virulence as measured by the LD_（50） of 2.12×10~5 CFU/mL and1.46 ×10~7 CFU/mL.This research confirmed that the pathogen of the diseased pigs was P.mirabilis,and suggested to use the highly sensitive antibiotic drugs on clinical treatment.