Abstract:

Objective To study the antibacterial activities of 95% ethanol extract
of Yinhuamiyanling Tablets in Eschericha coli  (E. coli) standard strains and clinical drug-resistant strains in vitro,and to clarify the antibacterial mechanism.
Methods Cylinder-plate method was used to test the antibacterial activities of Yinhuamiyanling Tablets of 95% ethanol extract on E.coli standard s
train ATCC25922 and 18 strains of urinary tract infection clinical E.coli producing extended spectrum β-lactamases (ESBLs),and the minimum bactericidal concentration (MBC) was determined.The bacterial ultrastructural changes were observed by scanning and transmission electron microscope before and after the drug application.Results The MBC50 and MBC90 of 95% ethanol extract of Yinhuamiyanling Tablets in  E.coli standard strain ATCC25922 and clinical E.coli producing ESBLs were 100 g/L^-1 and 150-250 g/L^-1.The E.coli cells showed surface collapse,depression and thorn-like protuberances at both ends,severely deformed under  scanning electron microscope after treated with 95% ethanol extract of Yinhuamiyanling Tablets;negative staining revealed that the bacterial refraction deteriorated under transmission electron microscope,bacteria deformation appeared to fold,and part of
the cell wall were depression;the negative staining  transmission electron microscope results  showed  bacteria shrinkage,swelling,the cell wall blurred or even
 missed,and the cytoplasm was pyknotic and disintegration to small vacuoles.Conclusion 95% ethanol extract of Yinhuamiyanling Tablets  has a certain degree of inhibitory effect on E.coli standard strain ATCC25922 and E.coli producing ESBLs,and its mechanism may be related to its interference or disruption of the E. coli
cell wall synthesis or destruction of large molecular proteins,which results in  the ultrastructural changes of E.coli.
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Key words: Yinhuamiyanling , Tablets;ethanol extract;Escherichia coli;electron microscope;antibacterial mechanism