Panton-valentine Leukocidin Expression in Community Associated Methicillin Resistant Staphylococcus Aureus Isolates from Rural Alaska

AND SPECIFIC AIMS Incidence of infection by Methicillin resistant Staphyloccocus aureus (MRSA) has historically been attributed to nosocomial sources, but there is currently an increasing trend towards community acquired infection not associated with hospital settings. Community-associated MRSA (CA-MRSA) is most often associated with skin and soft tissue infections rather than invasive disease. ii,iii,iv,xiv The majority of isolates causing skin infections in healthy people carry a gene for a toxin called Panton-Valentine leukocidin (PVL). Presence of the PVL gene in the majority of community-associated human skin infections has led to general acceptance for PVL as an important virulence factor. One recent study, however, has suggested that presence of the PVL gene has no effect on MRSA virulence vi and so this has become a point of contention in the understanding of the pathogenesis of these infections. The objective of this experiment is to verify if PVL is indeed a virulence factor in community associated-MRSA (CA-MRSA) by studying isolates collected from a skin infection outbreak in rural communities in southwestern Alaska. This experiment will detect and quantify the expression of PVL by studying messenger ribonucleic acid (mRNA). PVL mRNA levels will be measured using reverse transcriptase real-time polymerase chain reaction (RT-PCR). I am hoping to determine whether or not CA-MRSA strains that carry the PVL gene are actually producing the PVL toxin. Isolates that were found to cause infection (invasive strains) will be compared to strains that were not found causes infection (carrier strains). If findings show that the PVL gene expression is higher in invasive strain than in carrier strains, then it can be suggested that PVL plays a role in the pathogenicity of CA-MRSA skin infections. If PVL expression levels do not show a pattern between carrier and invasive isolates of the same outbreak, this might provide supporting evidence for an alternate mechanism of infection.