Study On The AdeABC Efflux Pump And Muti-resistance Of Acinetobacter Baumannii

BackgroundAcinetobacter baumannii(A.baumannii) has emerged as an important nosocomial pathogen that is responsible for a variety of nosocomial infections,comprising baeteremia,urinary tract infection,secondary meningitis,surgical-site infection,and nosocomial and ventilator-associated pneumonia.In recent years,several outbreaks of nosocomial infections patients,especially in intensive-care-unit(ICU) and blood ward caused by multi-resistant A.baumannii have been documented.Because of the multiple antibiotic resistance exhibited by A.baumannii,nosocomial infections caused by this organism are difficult to treat.To provide measures for choosing properly clinical antimicrobials,and controlling the nosocomial infection of multi-drug A.baumannii,it is significate to study the multidrug-resistant mechanisms.ObjectiveAcinetobacter,which were resistant to theβ-lactam,quinolones,aminoglycosides at the same time,were defined as multi-resistance strains.Recently,efflux pump has been proved to be an important factor leading to multi-resistance.Our study is to screen the drug resistance of A.baumannii,to investigate affection of effiux inhibitor;to detect the effiux genes and their DNA sequence of A.baumannii.This study will play an important role in tracking the changes of the resistant mechanism of A.baumannii in this region.MethodsResistance monitoring results to ten kinds of clinical antimicrobials during the year of 2001 to 2007 were retrospective analyzed.50 strains of A.baumannii were identified by Vitek 2 system.K-B test was carried out to detect the susceptibility of 12 antimicrobial agents to choose multidrug A.baumannii.MICs of antibiotics that ofβ-lactam,fluoroquinolones and aminoglyeosides combined CCCP and reserpine against A.baumannii were assayed by agar dilution method.Specific primers of adeB,adeR and adeS were designed to detect incidence of effiux pump genes by PCR.The DNA sequencing were BLAST on GenBank,analyzing arrangement of all genes.ResultsThe range of MICs to ciprofloxacin,cefotaxime,amikacin and imipenem was 1-128μg/ml,128-512μg/ml,16-128μg/ml,32-1024μg/m,respectively.Effiux pump inhibitor(reserpine and CCCP) enhanced the activities of the four antibiotic agents.At least four fold decrease of MIC was observed with reserpine in 49,50,50 and 46 isolates for ciprofloxacin,cefotaxime,amikacin and imipenem,respectively;otherwise, 21,44,26 and 48 with CCCP.There was different effects between the two effiux pump inhibitors.94%,96%and 92%of 50 multi-resistance A.baumannii was detected for adeB,adeR and adeS gene,respectively.ConclusionThe susceptibility rate of A.baumannii toβ-lactam,quinolones and aminoglycosides was decreasing year by year.The present study discovered that detection rate of genes was high,and effiux pump inhibitor(reserpine and CCCP) can increase the the vitro-activities of the four antimicrobial agents,obviously.This indicates the relationship of the effiux pump and multi-resistance and the exsistance of other pump.Our results will serve as a basis for monitoring the future changes associated with the emergence and spread of multi-resistance in this region.