Comparison between Antimicrobial Minimal Biofilm Eradication Concentration and Minimal Inhibitory Concentration in Clinical Isolates in Device Related Infections

Abstract

Background: Biofilms have been defined as complex microbial assemblages anchored to abiotic or biotic surfaces. This microbial assemblage may harbor single or multiple microbial populations or micro colonies. Biofilms play a pivotal role in device related infections (DRIs). Formation of biofilm on medical devices is a growing problem. Objectives: we aimed to compare between the minimal biofilm eradication concentration (MBEC) of sessile cells of biofilm forming isolates and minimal inhibitory concentration (MIC) of their planktonic counterpart in device related infections. Methodology: This study was conducted on 90 patients divided into three groups according to device associated health care associated infections (DA-HAI). Group I included 30 patients with central line-associated blood stream infection (CLABSI), group II included 30 patients with catheter associated urinary tract infection (CAUTI), and group III included 30 patients with ventilator associated pneumonia (VAP). Detection of biofilm formation was done using tissue culture plate and antibiotic susceptibility of biofilm forming bacterial isolates was done by disc diffusion method. MIC and MBEC were done only for biofilm forming isolates. Results: Out of 79\90 bacterial isolates, 23 isolates (29%) were biofilm forming. There was statistically significant difference between MIC and MBEC of vancomycin and levofloxacin tested for gram positive biofilm forming bacterial isolates (p<0.05) and between MIC and MBEC of imipenem and levofloxacin. For both gram positive cocci and gram negative bacilli; isolates which were sensitive or intermediately sensitive in the MIC values showed resistance in their MBEC values. Conclusion: The difference between MBEC and MIC was statistically highly significant. Thus, it is recommended to detect MBEC rather than MIC to antimicrobials for treatment of DRIs.