Active Efflux-Medicated Drug Resistance In Acinetobacter Baumannii

Acinetobacter baumannii was conditioned pathogen and important hospital infection pathogenic bacteria, which caused pneumonia, urinary system infection, meningitis and so on. With the clinically extensive use of antimicrobials, drug resistance of A. baumannii was more and more serious. Accordingly, it has been the focus of much interest about the research for the drug resistance mechanism and how decrease drug resistance strains of A. baumannii.It has been researched that A. baumannii can be caused resistance against antimicrobials by many means, such as producing inactive enzyme, genic mutation, integronic gene diffusion and decreased permeability of pellicle and so on. However, it has been thoroughly illuminate about another important mechanism of bacterium that active efflux-medicated drug resistance in A. baumannii. Little research has been done on active efflux mechanism in A. baumannii, while it has been not reported about efflux pump gene-medicated drug resistance in A. baumannii. It has only been reported that there may be active efflux system AbeABC and efflux pump AbeM. This study was designed to study the drug resistance mechanism associated with efflux pumps in the clinical isolates of A. baumannii, which by detecting the distribution and express of adeB and abeM gene in isolates of A. baumannii.In this study, agar dilution method was used to determine the minimum inhibitory concentrations (MIC) of 8 antimicrobials against 37 isolates of A. baumannii and the changes of MICs by carbonyl cyanide m-chlorophenylhydrazone (CCCP), polymerase chain reaction (PCR) was used to detect the gene encoding the muti-drug resistant active efflux pump and semi-quantitative reverse transcriptase polymerase to chain reaction (RT-PCR) was used to detect the m RNA expression levels of adeB gene in the isolates of A. baumannii.The results indicated that the clinical isolates of A. baumannii were different degree resistant against most antimicrobials. There were high ratio of drug resistance and many mutildrug resistant strains. After 37 isolates of A. baumannii were treated by CCCP, the MICs of the antimicrobials against the isolates of A. baumannii showed the different degree depress. There were muti-drug resistance and active drug efflux in the clinical isolated strains. AdeB gene and abeM gene were detected in all strains. The levels of mRNA expression of adeB gene and abeM gene in muti-drug resistanct strains were obviously higher compared with the susceptible ones (P<0.01) and unitary resistant ones (P<0.05).The experiment results indicated that the situation of drug resistance in A.baumannii was serious. Mutildrug resistance was gradually obvious. Many clinical commonly used antimicrobials were worse exosomatic antibacterial activity against isolates of A. baumannii. Carbopenems was only better antibacterial activity in 8 antimicrobials. There was generally active efflux system in the isolates of A. baumannii. One of mutildrug resistance mechanism of A. baumannii may be caused high level expression of adeB and abeM gene encoding efflux system.