Virulence of functions of proteobacterial antimicrobial compound efflux (PACE) family of transport proteins

Acinetobacter baumannii is a significant hospital-acquired pathogen due to its traits such as multidrug resistance. Multidrug efflux systems are one of the major causes of resistance to many antimicrobials in pathogenic bacteria. The multidrug efflux pumps in bacterial pathogens also play an important role in a range of cellular activities other than drug resistance, such as virulence, biofilm formation and the export of secondary metabolites. Recent data using mouse and insect larval models suggest that the novel multidrug efflux pump AceI may play an important role in animal colonization and virulence. This project investigated the potential virulence functions of the aceI gene by performing a range of assays including growth in human serum, attachment to biotic and abiotic surfaces and iron starvation. It was found that aceI is not required for the overall fitness of the AB5075-UW for the growth in laboratory media or for the survival of this strain under iron-limiting conditions. However, an aceI knockout strain was not viable for growth in 100% human serum. Therefore, aceI might play a role in providing resistance to a component of human serum. Furthermore, biofilm formation and quorum sensing studies also suggested potential involvement of aceI in the pathophysiology of AB5075-UW.