Published: 17 Dec 2014 | Last Updated: 18 Dec 2014 08:07:51

 A new study involving RVC researchers has been published relating to the identification of bacterial proteins identified in Staphylococcus aureus tempering with the immune response.

The epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) has changed dramatically over the past 15 years. Initially a nosocomial pathogen, newly emergent strains of MRSA have become increasingly common in the community among individuals lacking contact with healthcare. More recently, a third group of MRSA strains have been identified in association with livestock, particularly swine. These strains, termed livestock-associated MRSA, have now been identified in Europe, North America, and Asia in humans and animals.

One molecular type, ST398, has been the dominant strain of livestock-associated MRSA identified to date. The emergence of this strain in animals and humans, and the ease with which it spreads between different species, has puzzled researchers. Although genetic analysis of the genes encoding the major virulence factors revealed the presence of the same genes in all strains studied, the results demonstrated spa type crossing alterations in adhesion abilities in addition to a strongly enhanced lysis activity directly linked to impaired clearance attributable to cells of the innate immune system. This change in virulence pattern indicates high heterogenicity in the ST398 pool that is not based on a different genetic make-up, but probably on variations in the genetic regulation systems.

Researchers at the RVC have now identified two modifications, which are potentially tightly connected to pathogenicity, and which are potentially involved with a bacteria-associated over-activation of the immune system, potentially resulting in some of the clinical signs observed during infections with this specific MRSA strain.  

Citation: 
Patterson, NJ; Günther, J; Gibson, AJ; Offord, V; Coffey, TJ; Splitter, G; Monk, I; Seyfert, HM; Werling, D. (2014)
TwoTIR-like domain containing proteins in a newly emerging zoonotic Staphylococcus aureus strain sequence type 398 are potential virulence factors by impacting on the host innate immune response.
Frontiers in Microbiology, 5;662.