Analyse der Interaktion von Acinetobacter baumannii mit humanen epithelialen Zellen

Abstract

Acinetobacter baumannii causes severe nosocomial infections such as pneumonia, meningitis and sepsis with high mortality rates. This organism represents an increasing danger for immunocompromised adults, especially since there are an increasing number of resistances against antibiotics. Until now, scientific investigation was mainly focused on taxonomy and antibiotic resistance mechanisms. The goal of this project was to analyse the interaction between clinical strains of Acinetobacter baumannii and human cells in order to address the molecular mechanisms causing pathogenicity. Adherence is the first step in colonization of human tissue, and therefore a key event in pathogenesis. To demonstrate the adhesion of bacteria to human cells, a colony counting assay has been established. These experiments used the the type strain of A. baumannii ATCC 19606, as well as clinical isolates. All A. baumannii strains investigated showed adhesion to the lung epithelial cells A549, but the adhesion capacity was variable for the different strains. Furthermore, transposon mutagenesis of A. baumannii has been established in order to be able to search for components that are involved in adherence. A highly efficient Tn5 derivative was used for transposon mutagenesis of several species of Acinetobacter, as well as of Pseudomonas fluorescens as a control. Additionally a biofilm-testing assay was established to investigate biofilm formation of A. baumannii on polystyrol microtiter dishes. Biofilm formation was quantified by staining with crystalviolet followed by solubilization with ethanol. All investigated A. baumannii strains showed biofilm formation but with different capacity. No relationship between adhesion capacity of the different investigated A. baumannii isolates and the ability of biofilm formation was observed in this work.