Study On The Resistance Mechanisms And Molecular Epidemiology Of Multi/Pandrug-resistance Acinetohacter Baumannii

Objective:To analysis the antimicrobial resistance of19kinds antibiotics includingtigecycline, colistin and rifampin. To study a part of resistance genes (Class Dcarbapenemases gene and intergrons) carried of Multidrug-resistance Acinetobacterbaumannii (MDR-Ab) even pandrug-resistance Acinetobacter baumannii(PDR-Ab) inthe hospitals of North Anhui. In order to guide clinicians on decisions regarding thebest therapeutic approach for patients with MDR/PDR-Ab infections. The molecularhomology of this MDR/PDR-Ab were investigated, which provides the strategies ofcontrolling the prevalence of MDR/PDR-Ab in nosocomial.Methods:1. We retrospectively analysised and collected72strains of Acinetobacter baumanniifrom three hospitals of northern Anhui. Bacterial identification were carried out usingGNI card of VITEK-32. The minimal inhibitory concentrations(MIC) of the16kindscurrently used antimicrobial agents were detected by GNS-148card. Theantimicrobial susceptibility testing of tigecycline, colistin and rifampin wereperformed by broth dilution method.2. Class D carbapenemases gene(blaoxa-51-like,blaoxa-23-like,blaoxa-24-like,blaoxa-58-like) and integrase genes of intergrons frome class1to3were amplified bypolymerase chain reaction(PCR).3. The repetitive extragenic palindromic sequence-based PCR (REP-PCR) wasproformed for stain identification.Results:1. Of the72Acinetobacter baumannii strains,75%(54/72)were multiresistant strainsand25%(18/72)were panresistant strains. Infections of MDR/PDR-Ab took placewidely, respiratory infection(rates of up to86.11%) was mostly found and the cases were potencially gathered in ICU wards(62.50%).2. The results of drug sensitivity showed that tigecycline, colistin and rifampin wereeffective againist the MDR/PDR-Ab in vitro, the resistant rates were5.56%,6.94%and16.67%, respectively. The lowest rates of16kinds currently used antibiotics wascefoperazone-sulbactam(41.67%). While, the sensitivity to2kinds of carbopenemsantibiaotics was imipenem76.39%and meropenem77.78%. All isolates showed nearly100%resistance to others antibiotics. Furthermore, the study found that a strain wassensitive to imipenem but not to meropenem.3. Among the72strains, all possessed blaoxa-51-like carbapenemase gene and84.72%(61) carried blaoxa-23-like carbapenemase gene. In our study, blaoxa-24-likeand blaoxa-58-like carbapenemase gene were not researched.4. In72MDR/PDR-Ab,66(91.67%) harbored Class1integron, but integrase genes ofclass2and3intergrons were not detected.5. Patterns of REP-PCR were same in the strains from the People’s Hospital ofHuaibei, which told us that it was the same strain spreading in the hosptial. Therewere three patterns spreading in the First Affiliated Hospital of Bengbu MedicalCollege and two patterns in the Third Affiliated Hospital of Bengbu Medical College.But the strips of eight strains in the Third Affiliated Hospital of Bengbu MedicalCollege were not clear, which still could not determine whether only two differentstrains in the spread. Fortunately, we didn’t find the same strain spreading amongdifferent hosptials.Conclusions:1. Clinical isolates of Acinetobacter baumannii in this study had shown multiresistant,even panresistant strains. The resistant stage to currently used antibiaotics was serious,but the cefoperazone/sulbactam was the first chinical choice compared to otherantimicrobial agents.2. Tigecycline, colistin and rifampin remained good susceptibility againstMDR/PDR-Ab. OXA-23carbapenemases was the most prevalent enzyme inMDR/PDR-Ab, but there was not strict one-to-one relationship between positivestrains and imipenem resistance. Therefore, We speculated that it must exist other resistant mechanism permitting the strains against carbapenem.3. The study indicated that positive rates of Class1integron was higher than reported,however, revealed that it participate in multirug-resistance or pandrug-resistance.4. We found that clones of MDR/PDR-Ab had spread widely among wards in thehospitals. There were one or few strains of MDR/PDR-Ab outbreak in the samehospital. It suggest that we should strength the measures of nosocomial infections.