In vitro production of panton-valentine leukocidin among strains of methicillin-resistant Staphylococcus aureus causing diverse infections.
BACKGROUND
Community-acquired methicillin-resistant Staphylococcus aureus strains have recently been associated with severe necrotizing infections. Greater than 75% of these strains carry the genes for Panton-Valentine leukocidin (PVL), suggesting that this toxin may mediate these severe infections. However, to date, studies have not provided evidence of toxin production.


METHODS
Twenty-nine community-acquired methicillin-resistant Staphylococcus aureus and 2 community-acquired methicillin-susceptible S. aureus strains were collected from patients with infections of varying severity. Strains were analyzed for the presence of lukF-PV and SCCmecA type. PVL production in lukF-PV gene-positive strains was measured by ELISA, and the amount produced was analyzed relative to severity of infection.


RESULTS
Only 2 of the 31 strains tested, 1 methicillin-resistant Staphylococcus aureus abscess isolate and 1 nasal carriage methicillin-susceptible S. aureus isolate, were lukF-PV negative. All methicillin-resistant Staphylococcus aureus strains were SCCmec type IV. PVL was produced by all strains harboring lukF-PV, although a marked strain-to-strain variation was observed. Twenty-six (90%) of 29 strains produced 50-350 ng/mL of PVL; the remaining strains produced PVL in excess of 500 ng/mL. The quantity of PVL produced in vitro did not correlate with severity of infection.


CONCLUSIONS
Although PVL likely plays an important role in the pathogenesis of these infections, its mere presence is not solely responsible for the increased severity. Factors that up-regulate toxin synthesis in vivo could contribute to more-severe disease and worse outcomes in patients with community-acquired methicillin-resistant Staphylococcus aureus infection.
Hamilton
Stephanie M
SM
Veterans Affairs Medical Center, Boise, Idaho 83702, USA.
Bryant
Amy E
AE
Carroll
Karen C
KC
Lockary
Vivian
V
Ma
Yongsheng
Y
McIndoo
Eric
E
Miller
Loren G
LG
Perdreau-Remington
Francoise
F
Pullman
John
J
Risi
George F
GF
Salmi
Daniel B
DB
Stevens
Dennis L
DL
D001427:Bacterial Toxins / Q000378:metabolism*; D005098:Exotoxins / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D007956:Leukocidins / Q000378:metabolism* / Q000502:physiology; D016106:Methicillin Resistance; D013203:Staphylococcal Infections / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000187:drug effects / Q000378:metabolism* / Q000472:pathogenicity; D037521:Virulence Factors / Q000378:metabolism*
D001427:Bacterial Toxins; D005098:Exotoxins; D007956:Leukocidins; C078284:Panton-Valentine leukocidin; D037521:Virulence Factors