Effect of biofilm formation on the survival of Acinetobacter baumannii on dry surfaces

Background: Acinetobacter baumannii is emerging as an important hospital pathogen, which can persist in the environment for extended periods of time. It is known to produce biofilms, a community of bacteria enclosed within a protective polymeric matrix. Aim: To establish whether the effect of biofilm formation by Acinetobacter baumannii may be associated with persistence in the hospital environment. Methods: The effect of biofilm formation on the survival of A. baumannii on dry surfaces was investigated in biofilm-forming compared to non-biofilm-forming strains. Survival assays were determined by viable counts of the cells inoculated on to glass cover slips and stored under controlled conditions of temperature and relative humidity. Findings: The survival times for the biofilm-forming strains were longer than for the non-biofilm-forming ones (36 vs 15 days, respectively, P < 0.001). Scanning and transmission electron microscopy studies showed a polysaccharide layer and appendages in the biofilm-forming strains, not in the non-biofilm forming ones. Conclusion: Biofilm formation increases the survival rate of A. baumannii on dry surfaces and may contribute to its persistence in the hospital environment, increasing the probability of causing nosocomial infections and outbreaks. (C) 2011 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.