Correlation Between Efflux Pump AdeFGH And Multidrug Resistance Acinetobacter Baumannii

Objective:To investigate the clinical distribution and drug resistance of60clinical isolated strains of Acinetobacter baumannii, and to discuss distributions of active efflux system genes adeF, adeG and adeH in A. baumannii together with their relationships between mRNA expression level and multidrug resistance (MDR) of A. baumannii, thus providing a theoretical basis for the guidance in proper use of antibiotics in clinical, the inhibition of the growth and transmission of drug-resistant strains as well as the research and development of new antibacterial agents.Methods:Specimens of sputum, wound secretion and others were collected from different departments, where A. baumannii was isolated by plate screening and determined by BDTM CrystalTM Identification System. Drug susceptibility testings for20drugs were made in60clinical A. baumannii isolates by BioMerieux ATBTM test strips, and then a statistical analysis was performed. Gene sequences of A. baumannii, adeF, adeG and adeH, were found in GenBank; primers were designed by Lasergene8.1.3; the clinical distributions of efflux pump genes, adeF, adeG and adeH, in A. baumannii collected were detected by polymerase chain reaction (PCR); mRNA expression levels of efflux pump genes, adeF, adeG and adeH, in A. baumannii collected were detected by real-time PCR (Real Time PCR, RT-PCR), and their relationships with MDR of A. baumannii were analyzed.Results1. Sixty strains of A. baumannii were majorly from ICU (46.7%), neurosurgery department (15%) and others; the distribution of specimens was majorly sputum specimen (78.3%), followed by wound secretion specimen (11.7%), and other types accounted for10%. And they were divided into three groups according to the results of drug susceptibility test:24strains in Group A (pan-drug resistant,40%%),26ones in Group B (susceptive to aminoglycosides and bactrim, resistant to other antibiotics,43.3%) and10ones in Group C (resistant to amoxicillin and first/second generation cephalosporins, susceptive to other antibiotics,16.7%).2. In60clinical A. baumannii isolates, efflux pump genes adeF, adeG and adeH were detected in both Group A and B; while in Group C, adeF was detected in2strains, adeG in10strains and adeH in3strains, with no strain possess genes adeF, adeG and adeH simultaneously. The results indicated that the co-existence of adeF, adeG and adeH of efflux pump AdeFGH related to MDR of A. baumannii under the circumstances of possessing genes adeF, adeG and adeH simultaneously only.3. In terms of mRNA expression levels of adeF and adeG, no significant difference was found among the three groups; in terms of mRNA expression level of adeH, there was no significant difference between Group A and B (p>0.05), with significant difference between Group A and C or between Group B and C (p<0.05); however, higher expressions mRNAs of adeH was observed in some strains of Group C. Which suggested that efflux pump AdeFGH played a role of excretion in A. baumannii when genes adeF, adeG and adeH expressed simultaneously only.Conclusion1. Drug resistance so far is severe in clinic isolated strains of A. baumannii in Hengyang, and most of them are MDR or PDR strains;2. Active efflux pump AdeFGH may be related to MDR of A. baumannii in Heangyang;3. MDR of A. baumannii in Hengyang may be related to co-existence and co-expression of adeF, adeG and adeH.