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OBJECTIVE： To investigate in vitro antibacterial activity of the extracts from the root， stem and leaves of Psychotria rubra， and to investigate its mechanism of antibacterial effects. METHODS： 95％ ethanol extracts from the root， stem and leaves of P. rubra were used to prepare solution with mass concentration of 100 mg/mL （calculated by extract）. Using as penicillin sodium （0.5 mg/mL） and streptomycin sulfate （128 mg/mL） as positive control， plat stiletto method was used to determine antibacterial effects of the extracts from different parts of Staphylococcus aureus， Escherichia coli， Pseudomonas aeruginosa， Bacillus subtilis， Micrococcus luteus and Enterococcus faecalis. Using systematic solvent extraction method， the petroleum ether， ethyl acetate and n-butyl alcohol were used to extract antibacterial activity parts from P. rubra as ad to obtain the extracts of corresponding polar parts. After preparing 100 mg/mL drug solution （calculated by extract）， antibacterial effects of above 6 kinds of bacteria were investigated. The micro-broth dilution method and agar culture medium plate method were used to determine minimum inhibitory concentration （MIC） and minimum bactericidal concentration （MBC）， and screen polar parts with bacteriostasis and drug-sensitive strains. Under the concentration of 0.5MIC and MIC， the growth curves of sensitive bacteria were drawn （treated for 36 h， every 4 h）； the contents of alkaline phosphatase （AKP） and soluble protein were detected in suspension （treated for 10 h， every 2 h）； bouillon culture medium instead of the extract as blank control. RESULTS： 100 mg/mL ethanol extracts from the root， stem and leaves of P. rubra showed good antibacterial effect to above 6 kinds of bacteria， in descending order as stem＞leaves＞root. Among different polar parts from the stem of P. rubra， antibacterial effect of the ethyl acetate extract was best， especially for the S. aureus， the diameter of inhibition zone reached （38.93±0.12） mm， and both MIC and MBC were 0.39 mg/mL. The ethyl acetate extract could significantly inhibit the proliferation of S. aureus， and its alkaline phosphatase and protein content in suspension were increased significantly compared with blank control （P＜0.05）. CONCLUSIONS： The stem from P. rubra is effective antibacterial parts， and exhibit good antibacterial activity to 6 kinds of common pathogens. The ethyl acetate extract from the stem of P. rubra shows strongest antibacterial effect on S. aureus， and could gradually destroy the integrity of cell wall and cell membrane.
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Objective To investigate the antimicrobial activities of clove oil alone and in combination with three kinds of β-lactam antibiotics (amoxicillin, cephalexin, and cefepime) against methicillin-resistant Staphylococcus aureus (MRSA). Methods The minimum inhibitory concentrations (MICs) of clove oil alone and in combination with three kinds of β-lactam antibiotics against two standard MRSA and 32 MRSA isolated from clinic were determined by 96-well plate micro-dilution method. The fractional inhibitory concentrations (FICs) of clove oil and three kinds of β-lactam antibiotics were determined by using the micro-chessboard method. The growth curve of MRSA ATCC43300 effected by clove oil or clove oil combined with cephalexin was analyzed. Results Clove oil showed significant anti-MRSA activity in vitro, with MIC of 0.25 mg/mL and 0.51 mg/mL. The FICs were mainly distributed in the range of ≤ 0.5 and 0.5 to 1, and the synergy rates were 58.8%, 97.0%, and 64.7%, when the clove oil was combined with amoxicillin, cephalexin and cefepime, respectively. Clove oil enhanced the activity of β-lactam antibiotics against MRSA significantly, and reduced the dosage of it. The growth curve showed that the clove oil significantly inhibited the growth of MRSA, and prolonged its lag phase. And the effect showed a significant dose-effect relationship. The growth of MRSA was nearly inhibited when 1/4 MIC cefepime combined with 1/4 MIC clove oil. Conclusion Clove oil not only could exhibit strong anti-MRSA activity itself, but could enhance the activity of β-lactam antibiotics against MRSA. Hence, clove oil would be a potential new drug, which can be used as a new drug for preventing and treating MRSA infection.
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Objective: To study the antibacterial activity in vitro of Xiyanping injection combined with cefoxitin, cefuroxime, ceftriaxone, cefmenoxime, amikacin, levofloxacin and meropenem against staphylococcus aureus, escherichia coli, klebsiella pneumoniae, pseudomonas aeruginosa and acinetobacter bauman.Methods: Minimum inhibitory concentration (MIC) of the 7 kinds of antimicrobial agents used individually or combined with Xiyanping injection on germs were determined respectively on 96 plates by using the agar dilution method and the checkerboard method.Fractional inhibitory concentration index (FICI) was calculated to evaluate the antibacterial activity of Xiyanping injection combined with the 7 kinds of antimicrobial agents in vitro.Results: MIC of Xiyanping injection combined with cefoxitin was the same as that of cefoxitin used individually on escherichia coli.MIC of levofloxacin combined with Xiyanping injection showed no difference with that of levofloxacin used individually on klebsiella pneumoniae.Besides, Xiyanping injection could increase the MIC of the other antimicrobial agents on germs.Conclusion: Xiyanping injection combined with antimicrobial agents on staphylococcus aureus, escherichia coli, klebsiella pneumoniae shows antagonistic and irrelevant relationship.
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OBJECTIVE:To compare the in vitro antibacterial activity of azlocillin given alone with azlocillin plus tazobactam against168strains of clinically isolated pathogenic bacteria.METHODS:The antibacterial activities of two antibac_ terials against168strains of clinically isolated pathogenic bacteria in vitro were detected by two-fold dilution method.RE-SULTS:The MIC 50 and the MIC 90 of the combined therapy of azlocillin/tazobactam(4∶1)were1/32and1/64,respectively that of azlocillin given alone.CONCLUSION:The concomitant therapy of azlocillin with tazobactam improves the antibacterial activity.