Effects of four Tibetan medicinal extracts and antibiotics on biofilm of Clostridi-um perfringens
In order to investigate the inhibitory effects of extracts of Tibetan medicines and antibiot-ics on biofilm(BF)of Yak-derived Clostridium perfringens(C.perfringens),the minimum inhibi-tory concentration(MIC)of extracts of four Tibetan medicines extracted by three methods and twelve antibiotics against C.perfringens was determined by micro broth dilution method,and the combined inhibitory effects of extracts of Tibetan medicines and antibiotics were examined by u-sing checkerboard method.Crystalline violet staining was used to determine the film-forming abili-ty of 20 strains of C.perfringens BF and to test the inhibitory effects of Tibetan medicine extracts and antibiotics alone and in combination on BF.The results showed that the MIC of aqueous ex-tract of myrobalan was ≤0.80 g/L for 45.0％of C.perfringens strains;the MIC of 75％ethanol extract of pedunculate Herpetospermuan seed and methanol extract of Slender dutchmanspi pe fruit were ≤0.40 g/L for 20 strains of C.perfringens strains.The MICs of doxycycline and ampi-cillin against 19 strains of C.perfringens were ≤0.25 mg/L,and the MICs of vancomycin were both ≤0.50 mg/L.The 75％ethanol extract of myrobalan was more effective in bacteriostatic combination with gentamicin,producing a synergistic effect on 70.0％of C.perfringens.All20 strains of C.perfringens had BF film-forming ability,and 55.0％of the strains showed strong film-forming ability.Among the antibiotics examined,polymyxin B had the strongest inhibitory effect on BF,with a strong inhibitory effect at 1/4MIC.Among the examined Tibetan medicine ex-tracts,methanolic extract of Slender dutchmanspipe fruit and 75％ethanol extract of myrobalan showed strong inhibitory effect on BF at 1/2MIC.Gentamicin in combination with 75％ethanol ex-tract of myrobalan,and polymyxin B in combination with methanolic extract of Slender dutch-manspipe fruit remained strongly inhibitory to BF at 1/4MIC concentration in both.It shows that the extract of Tibetan medicine has inhibitory effects on C.perfringens and inhibits the formation of its BF,and the combination with antibiotics can enhance the inhibitory effect,which needs to be further researched on the mechanism of bacteriostatic inhibition of Tibetan medicine.
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