Resistant Mechanisms of Pan-drug Resistant Acinetobacter baumannii

OBJECTIVE To investigate the distribution of genes resistant to 7 kinds of antimicrobial agents: beta-lactams,aminoglycosides,quinolones,chloramphenicol,tetracycline,rifampicin,trimethoprim/sulfamethoxazole,and drug efflux genes,as well as genetic markers of conjugal plasmids,transposons and integrons in a strain of pan-drug resistant Acinetobacter baumannii(PDRABA) isolated from clinical sample.METHODS Drug susceptibility tests to 22 kinds of antimicrobial agents were detected by K-B disk diffusion tests.Then,73 kinds of resistant genes and genetic markers were analyzed by PCR and verified by DNA sequencing,including resistant genes to beta-lactams,resistant genes to aminoglycosides(aminoglycoside modifying enzyme genes and 16S rRNA methylase genes),resistant gene to quinolones of gyrA mutation,resistant genes to chloramphenicol,resistant genes to tetracycline,resistant genes to rifampicin,resistant genes to trimethoprim/sulfamethoxazole,and drug efflux genes,as well as genetic markers of conjugal plasmids,genetic markers of transposons,and genetic markers of integrons.RESULTS The strain of PDRABA was susceptible to cefoperazone/sulbactam,but resistant to other 21 kinds of antimicrobial agents.And 15 kinds of resistant genes and genetic markers were detected out: TEM,OXA-23,ADC,aac(3)-Ⅰ,aac(6′)-Ⅰb,ant(3″)-Ⅰ,aph(3′)-Ⅰ,tetB,mdfA,qacE△1-sul1,intⅠ1,tnpU,tnp513,ISaba1,and gyrA mutation.However,the rest 58 kinds of genes and genetic markers couldn′t be detected out.CONCLUSIONS The pan-drug resistance resulted from some kinds of resistant genes and genetic markers as well as drug efflux gene mdfA harboring on it.Furthermore,some kinds of mobile genetic elements harboring on the strain are prone tolead to horizontal dissemination of resistant genes and genetic markers.Thus,strict isolation measures should be enforced to patients infected with the strain of PDRABA.Andit′s the first report that a strain harbors resistant genes : TEM,OXA-23,ADC,aac(3)-Ⅰ,aac(6′)-Ⅰb,ant(3″)-Ⅰ,aph(3′)-Ⅰ,tetB,mdf A,qacE△1-sul1,intⅠ1,tnpU,tnp513,ISaba1 and gyrA mutation at the same ti me in China.