engleski

Effect of desiccation on interaction of multidrug-resistant Acinetobacter baumannii and free-living amoebae

Acinetobacter baumannii, is an important emerging hospital-acquired pathogen and is recognized as one of the the most difficult multidrug-resistant bacteria to control and treat. A. baumannii ability to survive under a wide range of environmental conditions and to persist for extended periods of time on surfaces makes it a frequent cause of intrahospital infection. The protozoa, especially amoebae, serve as natural reservoirs or vehicles for dissemination of several pathogenic bacteria but little is known about the interaction of free-living amoebae and A. baumannii. The aim of this study was to examine the survival of multidrug-resistant A. baumannii on a dry plastic surface and to test its ability of adhesion on free-living amoebae, Acanthamoeba castellanii. Bacterial strains used in this study were A. baumannii multidrug – resistant strain ATCC BAA-1605 and drug-sensitive strain ATCC 19606, as well as 4 clinical isolates (strains 771, 53154, 56781 and 54531). Bacterial inoculums were prepared in sterile tap water and 6 x 20 μl of bacterial suspension (~108 cfu/ml) were deposited in 96 wells plates and dried for one hour under laminar flow hood. At various intervals, the bacteria was rehydrated in sterile tap water and plated on LB agar to determine the number of viable bacteria. Bacterial viability was assessed with the Bacterial Viability Kit LIVE/DEAD® BacLight™ dying before fluorescent microscopy. At the same time, A. baumannii isolates exposed to desiccation were added to A. castellanii monolayers and bacterial adhesion after 2 hours were tested. The results showed that all A. baumannii strains, regardless of the antibiotic resistance, survive 100 days on dry plastic surfaces. Also, all A. baumannii strains exposed to desiccation were able to interact with amoeba A. castellanii up to 30 days. In conclusion, multidrug-resistant A. baumannii strains survive long period of time in dry conditions and are able to interact with amoeba. These results might have important implications for the role of amoeba in A. baumannii epidemiology. So, in hospital environment, special attention should be paid to the presence of free living amoebae and A. baumannii.

Acinetobacter; desiccation; survival; free-living amoebae

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