Comparison of MIC with MBEC Assay for <i>in Vitro</i> Antimicrobial Susceptibility Testing in Biofilm Forming Clinical Bacterial Isolates

Abstract

Context : MIC results can be misleading for treatment of biofilm associated. The Minimum Biofilm Eradication Concentration (MBEC) measure s the determination to be made for a biofilm susceptibility to antibiotics. Aims : Assessment of biofilm production and comparison of the MIC and MBEC assays evaluate differences in the antibiotic sensitivity patterns of different clinical bacterial isolates from patients implanted with medical devices. Settings and Design : Random sampling with experimental study at tertiary care institute. Methods and Material : The study was carried out during January 2014 to March 2014 on 50 positive bacteriological cultures of medical devices which were inserted in hospitalized patients. Biofilm forming strains were identified by tissue culture plate method & tube method. Biofilm-producing and non-biofilm forming reference strains were used as controls. Assay has been developed for the use with flat bottom, 96-well microtiter plates. Sterile autoclaved PCR tubes were used as pegs which provide d surface for the biofilm formation. Amikacin, ciprofloxacin, trimethoprim-sulfamethoxazole, vancomycin, cefoperazone/ sulbactam, gentamycin were tested for MIC and MBEC assay. Statistical Analysis Used : Results will be discussed in the form of percentages. Results : Colonization by Klebsiella pneumoniae , Acinetobacter baumanni and Pseudomonas aeruginosa w as prevalent bacterial isolates in medical devices. MBEC was higher for all the antibiotics as compared to MIC except amikacin MBEC for Pseudomonas was the same as MIC. Conclusions : Device associated bacterial biofilms are the major source of infections in patients of critical care setup. MIC misleads physician for organism’s drug susceptibility testing , which result s in therapeutic failure. MBEC can guide regarding choice and proper dosing of antibiotics to be given. That’s why major studies for similar testing should be done with clinical evaluation .