| 作者 |
Yin Xiangyu1#, Zhang Min2#, Li Ping2, Gao Wenwu2, Feng Weidong2, Ye Zhongmin2, Yang Danjiao2*, Chen Chaoxi1* |
| 摘要 |
[Objective] The paper was to was to screen sensitive drugs and their combinations against biofilm formation of Escherichia coli strains isolated from Tibetan pigs and Tibetan chickens. [Method] Semi-quantitative modified crystal violet staining and the micro broth dilution method were employed to assess the biofilm-forming capacities of 152 E. coli strains, as well as their susceptibility to 12 commonly used antibiotics. Meanwhile, checkerboard dilution method was employed to evaluate the combined antibacterial activity of the sequential solvent fractions (methanol, dichloromethane, ethyl acetate, and petroleum ether) from four Tibetan veterinary medicinal plants (Spenceria ramalana Trimen, Thalictrum delavayi Franch., Gentiana sino-ornata Balf. f., Lonicera rupicola Hook.f. & Thomson), the ethyl acetate extract of two Enterococcus faecium strains and antibiotics with high resistance rates [chloramphenicol (CHL), oxytetracycline (OTC), ampicillin (AMP), and sulfamethoxazole (SMZ)] against ten selected multi-drug resistant E. coli strains (designated E1-E10). Lastly, the clearance effects of various drug combinations on E6 biofilms of E. coli were examined. [Result] The majority of the 152 E. coli strains exhibited moderate and no biofilm-forming capacities. The resistance rates to CHL, sulfamethazine (SM2), OTC, AMP, and SMZ exceeded 90%. In contrast, the resistance rates to difloxacin (DIF), ciprofloxacin (CIP), amikacin (AMK), ceftiofur (EFT), tobramycin (TOB), and ceftriaxone (CTR) were below 50%. Notably, these strains demonstrated a higher susceptibility to amikacin, with a drug resistance rate of only 19.90%. The MIC values for the E. coli strains E1-E10 were observed to range from 3.93 to 15.63 mg/mL for the methanol extract of S. ramalana, from 3.93 to 31.52 mg/mL for the ethyl acetate extract of T. delavayi, from 7.81 to 15.63 mg/mL for the methanol extract of G. sino-ornata, and from 7.81 to 31.52 mg/mL for the ethyl acetate extract of L. rupicola. Additionally, the ethyl acetate extracts from E. aecium strains S16 and S17 exhibited MIC values ranging from 0.42 to 13.38 mg/mL and from 0.45 to 3.63 mg/mL, respectively. The combinations of sequential solvent fractions derived from four Tibetan veterinary medicinal plants, the ethyl acetate extract of E. faecium, and antibiotics exhibiting high resistance rates demonstrated varying effects. At the MIC, all drug combinations exhibited a more pronounced biofilm clearance effect compared to their individual applications. The ethyl acetate extracts of L. rupicola and T. delavayi, when combined with OTC and AMP, demonstrated a greater inhibitory effect on the E6 biofilm compared to other combinations. Specifically, the ethyl acetate extracts of L. rupicola and T. delavayi inhibited the E6 biofilm by 48.92% and 42.58% in the presence of OTC, and by 48.58% and 47.84% in the presence of AMP, respectively. [Conclusion] The combined application of four selected Tibetan medicinal plants, probiotics, and antibacterial agents may offer a potential solution to address drug resistance and biofilm formation in E. coli isolated from Tibetan pigs and Tibetan chickens. |
