Relationship Between Biofilm Formation Ability And Biofilm - Associated Gene And Drug Resistance Of Acinetobacter Baumannii

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 relationships among the three objects.Methods Biofilm models of 70 strains Acinetobacter baumannii that were collected in Chengwu county people’s hospital from Oct. 2012 to Oct. 2013 were constructed by using 96-well polystyrene plate in this prospective study. In order to analyze the bifilm-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. In addition, the expressions of biofilm-related protein Bap, biofilm-related gene bfs and classⅠ integrons gene int I1 were tested through PCR assay.Results Among all strains Acinetobacter baumannii, 40 strains were multi-drug resistant and 6 strains were pan-drug resistant, and 68 strains(97.14%) had biofilm-forming ability. In terms of the biofilm-forming ability, 14 of the 68 strains were found to be weakly positive, 20 positive and another 34 strongly positive. The antimicrobial resistant rate of Acinetobacter baumannii to imipenem, amikacin, meropenem and cefepime was 30.00%, 32.86%, 38.57% and 41.43%, respectively. However, the antimicrobial resistant rates to other commonly used antibiotics were higher than 50%. The drug resistance of Acinetobacter baumannii to levofloxacin(χ2=9.225,P=0.010), cefepime(χ2=7.222,P=0.027), gentamicin(χ2=6.601,P=0.037) significantly decreased when biofilm-forming ability reinforced. Bap gene positive rate of weakly positive, positive and strong positive biofilm-forming strains Acinetobacter baumannii was 50.00%, 65.00% and 79.41%(χ2=4.244,P=0.120), respectively. Bfs gene positive rate was 35.71%, 65.00% and 88.24%(χ2=13.602,P=0.001), respectively and int I1 gene positive rate was 42.86%, 75.00% and 91.18%(χ2=12.902,P=0.002), respectively. Moreover, the antimicrobial resistance of biofilm-related gene strains that were found to be positive was higher than that were found to be negative, in which the drug resistance of int I1 positive group to amikacin was significantly higher than the negative group(χ2=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、int I1, contributed to biofilm formation.