Characterisation of clinical and non-clinical strains of Acinetobacter and their virulence properties

Over the last few decades Acinetobacter baumannii has been documented around the globe as being a serious nosocomial pathogen among critically ill patients. This bacterium is capable of causing infections such as meningitis, septicaemia, urinary tract infections, endocarditis, skin and wound infections and respiratory infections. Infections are often complicated to treat due to the high levels of antibiotic resistance displayed by these bacteria. The aim of this work was to initially examine the potential virulence properties such as hydrophobicity, biofilm formation and the resistance of a collection of clinical and non-clinical strains of A. baumannii against a high number of beta-lactam antibiotics. The study was then investigated the presence of virulence genes commonly found among Gram-negative bacteria in these strains and looked at the interaction of these bacteria with a human gut epithelial cell line (Caco-2 cells) to identify the mechanism by which these bacteria translocate in the gut to cause septicaemia. The study ended with examining the role of a selection of known probiotic strains to inhibit the adhesion and translocation of these bacteria using the Caco-2 cells as a model. The results showed that both clinical and non-clinical strains of Acinetobacter belonging to different species, share many virulence potential and were capable of translocating in Caco-2 cells. It was also found that although both clinical and non-clinical isolates showed antibiotic resistance. Levels of antibiotic resistance were significantly higher in clinical isolates. This could be largely due to the possession of integrons. Extended spectrum beta-lactamases were not detected in either clinical or non-clinical isolates. Only one non-clinical isolate showed to produce metallo beta-lactamase enzyme.Submitted in the fulfilment of the requirements of the degree of Doctor of Philosophy, University of the Sunshine Coast, 2013