脆弱类杆菌与大肠杆菌混合感染的小鼠皮下脓肿模型的定量研究

Synergistic Effect of Bacteroides Fragilis and Escherichia coli on Induction of Subcutaneous Abscess and Mortality in Mice

本文用临床上厌氧菌感染中最常见的B.f(脆弱类杆菌)与兼性菌中最常见的E.c(大肠杆菌)作混合感染致病协同性研究的模式菌株,从定量角度建立小鼠皮下脓肿的感染模型。结果表明,单独在昆明小鼠皮下接种B.f 10~7(CFu/m)后1/10发生脓肿,10~8与10~9菌量分别有3/10及6/10发生脓肿。B.f的CP(荚膜多糖)提取物125μg、250μg、500μg,其脓肿形成率分别为1/10、2/10和4/10。单独注射E.c10~6～10~7菌量时,无脓肿及死亡发生。10~8时3/10小鼠死亡,脓肿不典型。引起感染的菌量阈值B.f为10~7,E.c为10~8。B.f致病特征为引起脓肿,E.c为引起死亡。混合感染两种菌浓度均在10~7时,5/10发生脓肿,2/10发生死亡。在感染灶中两种菌浓度总数分别保持在≥10~7。B.f与E.c混合感染时有明显的协同致死与协同致脓肿效应。

A mouse subcutaneous abscess model is established to evaluate the pathogenic synergy between B. fragilis and E. coil by using quantitative methods. Results showed that injection of B. fragilis alone subcutaneous into mice with 10~7 (CFU/ml), 10~8 and 10~9 results in abscess rates 1/10,3/10 and 6/10, respectively. CP of B. fragilis alone may cause subcutaneous abscess in mice. At the concentration of CP 125ug, 250ug and 500ug per milliliter,the abscess rates were 1/10,2/10 and 4/10, respectively. Inoculation of E. eoli alone with 10~6, 10~7, neither develope abscess nor died. At 10~8 of E. coli, 3/10 died with subcutaneous swelling but no tipical abscess. B. fragilis 10~7 mixed E. coli 10~7 lead to 5/10 mice developing abscess. Both death and abscess rates were markedly increased in the mixed infection. The B. fragilis and E. coli always remain≥10~7CFU/ml in the abscesses.