Correlation between the biofilm-forming ability, biofilm-related genes and antimicrobial resistance of Acinetobacter baumannii / 中华危重病急救医学

ABSTRACT

Objective To study the biofilm-forming ability and the distribution of biofilm-related genes in Acinetobacter baumannii clinical isolates as well as antimicrobial resistance,to analyze their relationships with the bacterial resistance phenotype.Methods A prospective study was conducted.Biofilm models of 70 strains Acinetobacter baumannii collected in Chengwu County People's Hospital from October 2012 to October 2013 were constructed using 96-well polystyrene plate.In order to analyze the biofilm-forming ability,a qualitative and quantitative analysis was conduct by crystal violet staining assay.And the antimicrobial resistance of different biofilm-forming ability strains was compared including imipenem,amikacin,meropenem,cefepime,sulbactam cefoperazone,trimethoprim,levofloxacin,gentamicin,ciprofloxacin,cefotaxime,ceftizoxime,aztreonam,piperacillin,ceftriaxone,cefuroxime.In addition,the expressions of biofilm-related gene Bap,bfs and intI1 were tested with polymerase chain reaction (PCR) assay.Results Among 70 strains Acinetobacter baumannii,40 strains were multi-drug resistant (57.14％) and 6 strains were pan-drug resistant (8.57％); 68 strains had biofilm-forming ability (97.14％),14 of which were weakly positive,20 were positive and 34 were strongly positive.The antimicrobial resistant rate of Acinetobacter baumannii to imipenem,amikacin,meropenem and cefepime was decreased,it was 30.00％,32.86％,38.57％ and 41.43％,respectively.However,the antimicrobial resistant rates to other commonly used antibiotics were all higher than 50％.The drug resistance of Acinetobacter baumannii to levofloxacin (85.71％,45.00％,38.24％,x2=9.225,P=0.010),cefepime (71.43％,45.00％,29.41％,x2=7.222,P=0.027),gentamicin (78.57％,55.00％,38.24％,x2 =6.601,P=0.037) was significantly decreased when biofilm-forming ability reinforced (weakly positive,positive,hadro-positive).Bap gene positive rate of weakly positive,positive and strong positive biofilm-forming strains Acinetobacter baumannii was 50.00％,65.00％ and 79.41％ (x2=4.244,P=0.120),respectively.Bfs gene positive rate was 35.71％,65.00％ and 88.24％,respectively (x2=13.602,P=0.001) and intI1 gene positive rate was 42.86％,75.00％ and 91.18％,respectively (x2 =12.902,P=0.002).Moreover,the antimicrobial resistances of biofilm-related gene positive strains were higher than the negative,of which the drug resistance of intI1 positive group to amikacin was significantly higher than the negative group (40.38％ vs.11.11％,x 2=5.194,P=0.023).Conclusions The Acinetobacter baumannii collected from the hospital had strong multi-drug resistance as well as strong biofilm-forming ability.The drug resistance of Acinetobacter baumannii decreased when biofilm-forming ability reinforced.In addition,genes,such as Bap,bfs,and intI1,contributed to biofilm formation.