利福昔明与精油对乳房炎源大肠杆菌抗菌效果评价

Evaluation of antibacterial effects of rifaximin and essential oils on Escherichia coli isolated from mastitis

旨在研究利福昔明(RIF)与3种精油,即桉叶油(EEO)、薄荷油(MEO)、鱼腥草油(HEO)对奶牛乳房炎源大肠杆菌的抑杀作用和对生物被膜的阻抑效果。自患乳房炎奶牛乳汁中分离47株大肠杆菌,微量肉汤稀释法测定RIF、精油对菌株的最小抑菌浓度(MIC)和最小杀菌浓度(MBC),棋盘法测定RIF与精油的联合抑菌指数(FICI)。结晶紫染色法检测生物被膜形成量,评价菌株形成生物被膜的能力,测定RIF、精油的最小抑膜浓度(MBIC),考察二者抑制被膜形成和消除预制被膜的效果。结果:RIF、EEO、MEO和HEO对大肠杆菌的MIC90分别为32μg/mL、2.5%、0.31%和0.63%。RIF与精油联合对多数菌株表现相加作用,其中RIF+EEO对80%的菌株表现相加作用。RIF、精油对84%以上菌株的MBIC/MIC为1-4,其中EEO对74%以上菌株该比值为1-2。1/2 MIC RIF或1/2 MIC EEO处理可使5株强成膜株的生物被膜形成率最低降至43.8%和5.8%,使其中4株菌的预制被膜留存率最低降至56.6%和44.8%。与RIF、EEO单独处理相比,1/2 MIC RIF+1/4 MIC-1/2 MIC EEO处理后5株强成膜菌被膜形成率和预制被膜留存率均显著降低(P<0.05)。RIF和3种精油对乳房炎源大肠杆菌均有较好的抗菌和抗生物被膜作用,二者联合作用更强,且以RIF+EEO的效果最优。

This study was to identify the inhibitory effects of rifaximin(RIF), eucalyptus essential oil(EEO), peppermint essential oil(MEO), and houttuynia essential oil(HEO) on the antibacterial activity and the biofilm of bovine mastitis-derived E. coli. 47 strains of E. coli were isolated from the milk of dairy cows inflicted with mastitis, the micro broth dilution method was used to determine the minimum inhibitory concentration(MIC) and the minimum bactericidal concentration(MBC), and the checkerboard method was used to determine the combined inhibitory index(FICI). The crystal violet staining method was used to determine the biofilm formation ability, the minimum biofilm inhibitory concentration(MBIC) and the effects of rifaximin and essential oils on the biofilm formation and preformed biofilm. The results showed that the MIC90 of RIF, EEO, MEO and HEO against E. coli were 32 μg/mL, 2.5%, 0.31%, and 0.63%, respectively. The combination of RIF and essential oil had an extra effect on most of the strains, of which RIF+EEO had an additive effect on 80% of the strains. The MBIC/MIC ratio of RIF and essential oil was 1-4 for more than 84% of the strains, and the ratio of EEO was 1-2 for more than 74% of the strains. The 1/2 MIC RIF or 1/2 MIC EEO treatments reduced the biofilm formation rate of 5 strong biofilm-forming strains to 43.8% and 5.8%, respectively, and reduced the preformed biofilm retention rate of 4 strains to 56.6% and 44.8%, respectively. Compared with RIF or EEO alone, 1/2 MIC RIF + 1/4 MIC-1/2 MIC EEO significantly reduced the biofilm formation rate and the retention rate(P<0.05). RIF and the three essential oils had good antibacterial and anti-biofilm effects on mastitis-derived E. coli. The combined effect of the two was stronger and RIF+EEO had the best effect.