Evaluation of Biofilm Formation in Multi Drug Resistant Isolates of Acinetobacter baumannii

Abstract

Acinetobacter baumannii is an important troublesome nosocomial pathogen and predominant cause of catheter and ventilator associated infections along w ith skin and bloodstream infections. The capability of multidrug resistant (MDR) A. baumannii to adopt various mechanisms of antimicrobial resistance against mUltiple classes of antibiotics enables its long-term survival in clinical settings and promotes the dissemination of MDR strains over the world. Biofilm forming ability of A. baumannii on both biotic and abiotic substrates is liable for high prevalence of hospital acquired infections, plays a key role in its pathogenesis and making alternative treatment options more challenging. The first objective of this research was to check the extended spectrum beta lactamase (ESBL) enzyme production in 100 clinical strains of A. baumannii and out of 100 only 28% strains were ESBL producers. ESBL producing strains were further screened for TEM-I, SHV-I and CTXM-I5 and their occurrence was 89%, 32% and 57% respectively. Biofilm formation potential of 100 clinical strains of Acinetobacter baumannii was also determined by microtiter plate and crystal violet staining method. Out of 100 only 35% strains were strong biofilm formers, 60% strains were moderate biofilm formers and only 5% strains were weak biofilm formers. Previous data showed that all these isolates were 100% sensitive to col istin. So, the present study also checked the effect of colistin on strong biofilm formers and compared its MIC-b with MIC-p of A. baumannii. MIC-p and MIC-b of isolate no 71, 72, 58 and 92 were performed by test tube method and microtiter plate method respectively and the values of MIC-p and MIC b of two isolates were same and two isolates have MIC-b values two-fold more than M1C-p. Last objective of this research was to check the minimum regrowth concentration (MRC) and minimum biofilm eradication concentration (MBEC) of colistin on strong biofilm formers of A. baumannii. The MRC values of strong biofilm formers are 8 folds more than MIC-p and MBEC values are 128 folds more than MIC-p of strong biofilm formers. So, our study indicated that higher concentration of colistin can completely eradicate the strong biofilm formers of MDR A. baumannii.