Characterisation of a staphylococcal type IB partitioning system in gram-positive hospital pathogens

Strains of methicillin-resistant Staphylococcus aureus (MRSA), coagulase-negative staphylococci (CNS), and vancomycin-resistant enterococci (VRE) that are resistant to multiple antimicrobial agents, are a major cause of hospital-acquired infections around the world and are responsible for significant morbidity and mortality. These Gram-positive pathogens commonly contain multiresistance plasmids that encode partitioning systems, which increase their segregational stability. Such systems contribute to the prevalence and spread of these plasmids, and effectively maintain resistance in the absence of selection. Three types (I-III) of partitioning systems are recognised based on centromere structure and type of motor/DNA binding protein. Putative Type Ib partitioning systems which have been identified on resistance plasmids from clinical staphylococcal and enterococcal isolates, contain candidate centromere-like site(s), and parA and parB genes that are predicted to encode a deviant Walker ATPase motor protein and a ribbon-helix-helix DNA binding protein, respectively. The overall aim of this study is to further characterise these Type Ib partitioning systems. In context of the staphylococcal system, chloramphenicol acetyltransferase assays have shown that the putative ParB protein regulates par operon transcription. Additionally, live-cell imaging via fluorescence microscopy has shown that a ParA-GFP fusion protein, which is functional in the absence of wild-type ParA, localises to the bacterial nucleoid.