Alpha-toxin promotes Staphylococcus aureus mucosal biofilm formation.
Staphylococcus aureus causes many diseases in humans, ranging from mild skin infections to serious, life-threatening, superantigen-mediated Toxic Shock Syndrome (TSS). S. aureus may be asymptomatically carried in the anterior nares or vagina or on the skin, serving as a reservoir for infection. Pulsed-field gel electrophoresis clonal type USA200 is the most widely disseminated colonizer and the leading cause of TSS. The cytolysin α-toxin (also known as α-hemolysin or Hla) is the major epithelial proinflammatory exotoxin produced by TSS S. aureus USA200 isolates. The current study aims to characterize the differences between TSS USA200 strains [high (hla(+)) and low (hla(-)) α-toxin producers] in their ability to disrupt vaginal mucosal tissue and to characterize the subsequent infection. Tissue viability post-infection and biofilm formation of TSS USA200 isolates CDC587 and MN8, which contain the α-toxin pseudogene (hla(-)), MNPE (hla(+)), and MNPE isogenic hla knockout (hlaKO), were observed via LIVE/DEAD® staining and confocal microscopy. All TSS strains grew to similar bacterial densities (1-5 × 10(8) CFU) on the mucosa and were proinflammatory over 3 days. However, MNPE formed biofilms with significant reductions in the mucosal viability whereas neither CDC587 (hla(-)), MN8 (hla(-)), nor MNPE hlaKO formed biofilms. The latter strains were also less cytotoxic than wild-type MNPE. The addition of exogenous, purified α-toxin to MNPE hlaKO restored the biofilm phenotype. We speculate that α-toxin affects S. aureus phenotypic growth on vaginal mucosa by promoting tissue disruption and biofilm formation. Further, α-toxin mutants (hla(-)) are not benign colonizers, but rather form a different type of infection, which we have termed high density pathogenic variants (HDPV).
Department of Experimental and Clinical Pharmacology, University of Minnesota Minneapolis, MN, USA.
Michele J
MJ
Anderson
Ying-Chi
YC
Lin
Aaron N
AN
Gillman
Patrick J
PJ
Parks
Patrick M
PM
Schlievert
Marnie L
ML
Peterson
D000818:Animals; D001427:Bacterial Toxins / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development*; D005260:Female; D055786:Gene Knockout Techniques; D006460:Hemolysin Proteins / Q000378:metabolism*; D018613:Microscopy, Confocal; D009092:Mucous Membrane / Q000382:microbiology; D009924:Organ Culture Techniques; D013194:Staining and Labeling; D013211:Staphylococcus aureus / Q000472:pathogenicity / Q000502:physiology*; D013552:Swine; D014621:Vagina / Q000382:microbiology
D001427:Bacterial Toxins; D006460:Hemolysin Proteins; C021091:staphylococcal alpha-toxin