Résumé
Aims: This study aimed to find out any synergism of gentamicin with the solvent extracts of small tropical herb Phyllanthus niruri to combat methicillin resistant Staphylococcus aureus. Methodology: Bioactive constituents of Phyllanthus niruri were extracted by macerating ground dry powder of the leaves in water, n-hexane, chloroform, methanol and ethanol for 48-72 h followed by filtration and evaporation of solvents. Microdilution method was used to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of these extracts. The synergistic effects between gentamicin and the extracts were evaluated by the checkerboard assay to calculate the fractional inhibitory concentration index (FICI). In all cases, ten hospital associated MRSA strains were used. Results: The MIC of aqueous and methanolic extracts of P. niruri against different MRSA strains varies from 3.125 mg/ml to 12.5 mg/ml. For the MRSA strain the combination of methanolic extract with gentamicin decreased the MIC of extract from 6.25 mg/ml to 0.2 mg/ml and the MIC of gentamicin from 2048 µg/ml to 256 µg/ml showing a strong synergistic effect with a fractional inhibitory concentration index of 0.157. Steroids, flavonoids, phenolic compounds and quinones identified in the extracts may play role in synergistic relation. Conclusion: The present investigation shows that bioactive constituents from Phyllanthus niruri have an excellent synergy with gentamicin against MRSA and can be further explored as an alternative anti-staphylococcal agent.
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Background & objectives: Multidrug-resistance of methicillin-resistant Staphylococcus aureus (MRSA) is a serious therapeutical problem. Chalcones belong to a group of naturally occurring flavonoids, usually found in various plant species, and have potent antibacterial, antiviral and antifungal activities. The goal of this study was to evaluate the antibacterial effect of three newly-synthesized chalcones against clinical isolates of MRSA, and their synergism with β-lactam and non- β-lactam antibiotics. Methods: Antimicrobial activity of the three newly-synthesized chalcones was tested against 19 clinical isolates of MRSA and a laboratory control strain of MRSA (ATCC 43300). The synergism with β-lactams: cefotaxime (CFX), ceftriaxone (CTX), and non-β-lactam antibiotics: ciprofloxacin (CIP), gentamicin (GEN) and trimethoprim/sulphamethoxazole (TMP-SMX) was investigated by checkerboard method. Results: All evaluated compounds showed significant anti-MRSA activity with MIC values from 25-200 μg/ml. Observed synergism with antibiotics demonstrated that chalcones significantly enhanced the efficacy of CIP, GEN and TMP-SMX. Interpretation & conclusions: oOur study demonstrated that three newly-synthesized chalcones exhibited significant anti-MRSA effect and synergism with non-β-lactam antibiotics. The most effective compound was 1,3-Bis-(2-hydroxy-phenyl)-propenone. Our results provide useful information for future research of possible application of chalcones in combination with conventional anti-MRSA therapy as promising new antimicrobial agents.
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Objective To evaluate the activity of antibiotics against pan-drug-resistant (PDR) Acinetobacter baumannii by combination antimicrobial susceptibility test in viro with epsilometric methods (Etest method) and microdilution checkerboard (CB method),and to detect a good correlation between timekill curve with the above mentioned two assays.Methods Thirty-one clinical isolates of PDR Acinetobacter baumannii were selected for mono and combination antimicrobial susceptibility test in vitro by E-test and CB method,then a comparison was conducted between the test results and the time-kill curve.Mono drugs involved tigecycline,colistin,imipenem and amikacin,and combinations involved two of drugs above,and three drugs involved imipenem/tigecycline,plus amikacin combination.Results Synergistic effect was detected in imipenem plus colistin and tigecycline plus imipenem combination.A high comparability was revealed between the E-test method with antimicrobial drugs added into the culture medium and the time-kill curves.Synergy in the combination of imipenem/tigecycline,plus amikacin was detected by the CB method and time-kill curves.Conclusion The results showed that the effect of specific combination of antibiotics against PDR Acinetobacter baumannii could be predicted by testing their synergistic effect with combination antimicrobial susceptibility test.
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Objective To evaluate the synergy effect of Meropenem and Sulbactam combination against Meropenem-resistant and Meropenem-susceptible A.baumannii in vitro and optimize combination ratio of Meropenem and Sulbactam to achieve best synergy effect.Methods Evaluating the synergy effect of Meropenem and Sulbaetam combination through microdilution checkerboard method against Meropenemresistant and Meropenem-susceptible A.baumannii,isolated from inpatients of Chinese hospitals.Assessing the synergy effect of combination in different ratios of Meropenem to Sulbactam.Results The checkerboard method with the combination of Meropenem and Sulbactam demonstrated 25.0％ ( 10/40 ) synergism,67.5％ (28/40) partial synergism,7.5％ (3/40) additive,no indifference and antagonism in Meropenemsusceptible isolates,and 27.5％ (11/40) synergism,40.0％ (16/40) partial synergism,25.0％(10/40) additive,no indifference and antagonism in Meropenem-resistant isolates.Eleven Meropenemresistant isolates which showed synergism in synergy test were tested for MICs of combination of Meropenem and Sulbactam,using ratios of 4∶ 1,2∶ 1,1∶1 and 1∶2,and the MIC90 were 64∶ 16,64∶ 32,32∶32,32∶64 μg/ml,respectively.Conclusions Meropenem and Sulbactam combination show synergism or partial synergism against most A.baumannii isolates.The optimal ration of combination for clinical use may be 1∶ 1.