Efflux mechanism on carbapenems of Acinetobacter baumannii / 中国基层医药

Objective To explore the drug fast mechanism on carbapenems of Acinetobacter baumannii,it is important for clinicians to choose appropriate antibiotics.Methods The influence of active efflux inhibitors carbonyl cyanide m -chlorophenylhydrazone (CCCP)on minimal inhibitory concentration (MIC)of Acinetobacter baumannii to imipenem(IMP)was measured by agar dilution method.Results At the concentration of 10mg/L,CCCP had obvi-ously effects on carbapenems MICs,the rate of resistance of imipenem decreased from 64.39% to 34.38%.In vitro CCCP enhanced the activities of imipenem.Efflux mechanism existed not only in IMP resistant strains,but also in IMP sensitive strains.But the affection of CCCP against IMP resistant strains was much stronger than that of IMP suscepti-ble strains.Conclusion Efflux pump may be one of the main mechanisms of Acinetobacter baumannii resistance to IMP,while efflux pump inhibitors may partly reduce the resistance.

Study of the role of efflux pump in ciprofloxacin resistance in Salmonella enterica serotype Typhi.

Purpose: There are increasing reports on failure of clinical response to ciprofl oxacin in typhoid fever despite the strain being sensitive to drug in in-vitro using standard guidelines and showing mutations in DNA gyrase. But this increased MIC and clinical failures with ciprofl oxacin are not always co-related with mutations presently identifi ed in gyrA and parC genes. This shows that there may be other mechanisms such as an active drug effl ux pump responsible as has been shown in other Enterobacteriaceae. This study was carried out to determine the role of effl ux pump in Salmonella Typhi isolates. Materials and Methods: Total 25 already characterized nalidixic acid sensitive and nalidixic acid resistant S. Typhi strains with different range of ciprofl oxacin MIC were included to study the role of effl ux pump in the presence of CCCP (effl ux pump inhibitor). For genotypic characterization, the entire acrR gene was sequenced to confi rm the presence of any mutation in the gene. Results: The MIC of ciprofl oxacin remained same in the presence and absence of CCCP in the studied strains and no signifi cant mutations were found in the acrR gene in any of the isolates studied. Conclusions: No role of effl ux pump in ciprofl oxacin resistance was found in strains studied. There is a need to explore further mechanism of ciprofl oxacin resistance in Salmonella Typhi.