Poster Presentation BacPath 13: Molecular Analysis of Bacterial Pathogens Conference 2015

Molecular analysis of an uncharacterised chaperone-usher gene cluster of Acinetobacter baumannii (#151)

Sharon Goh , Kimberly Kline 1 , Mark Schembri 2
  1. Singapore Centre for Environmental Life Sciences Engineering, School of Biological Sciences, Nanyang Technological University, Singapore
  2. Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia
Acinetobacter baumannii is a multidrug resistant pathogen associated with hospital outbreaks across the globe, particularly in the intensive care unit. The ability of A. baumannii to form biofilms allows it to survive in the hospital environment for long periods, causing ventilator-associated pneumonia, hospital-acquired bloodstream infection and urinary tract infection (UTI). Fimbriae play an important role in bacterial adhesion to host cells or inert surfaces as this is a vital step in the process of bacterial colonisation and biofilm formation. Many fimbrial adhesins bind to specific host receptors and thus represent essential virulence factors that define tissue tropism. We identified three chaperone-usher (CU) gene clusters (csu, fim1 and fim2) and the biofilm-associated protein (bap) from whole genome sequencing of two index case isolates within a collection of A. baumannii strains. Both Csu and Bap have been characterised previously. Here we studied the expression and function of an uncharacterised A. baumannii fimbrial cluster (referred to as fim2) in a collection of A. baumannii strains. A Fim2 major subunit-specific antibody was generated to demonstrate the expression of Fim2 in two A. baumannii UTI strains (M14 and M960), and this correlated with the ability of these two strains to adhere strongly to human uroepithelial cells. Immunofluorescence analysis showed that Fim2 is located at the cell surface of strains M14 and M960. Sequencing of the fim2 cluster of strains M14 and M960 revealed identical sequences, comprising of an ~5 kb operon encoding a major subunit, chaperone, usher and adhesin. The fim2 CU gene cluster was cloned and expression in a recombinant E. coli strain resulted in increased biofilm formation and adhesion to human uroepithelial cells. Finally, biofilm formation by the recombinant E. coli strain was abrogated by affinity-purified Fim2 major subunit-specific antibodies, demonstrating the direct contribution of Fim2 to biofilm formation in vitro.