AUTHOR=Anderson Michele J., Lin Ying-Chi , Gillman Aaron N., Parks Partick J., Schlievert Patrick M., Peterson Marnie 

TITLE=Alpha-Toxin Promotes Staphylococcus aureus Mucosal Biofilm Formation

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=2

YEAR=2012

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2012.00064

DOI=10.3389/fcimb.2012.00064

ISSN=2235-2988

ABSTRACT=<p><italic>Staphylococcus aureus</italic> causes many diseases in humans, ranging from mild skin infections to serious, life-threatening, superantigen-mediated Toxic Shock Syndrome (TSS). <italic>S. aureus</italic> 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 <italic>S. aureus</italic> USA200 isolates. The current study aims to characterize the differences between TSS USA200 strains [high (<italic>hla</italic><sup>+</sup>) and low (<italic>hla</italic><sup>−</sup>) 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 (<italic>hla</italic><sup>−</sup>), MNPE (<italic>hla</italic><sup>+</sup>), and MNPE isogenic <italic>hla</italic> knockout (<italic>hla</italic>KO), were observed via LIVE/DEAD® staining and confocal microscopy. All TSS strains grew to similar bacterial densities (1–5 × 10<sup>8</sup> CFU) on the mucosa and were proinflammatory over 3 days. However, MNPE formed biofilms with significant reductions in the mucosal viability whereas neither CDC587 (<italic>hla</italic><sup>−</sup>), MN8 (<italic>hla</italic><sup>−</sup>), nor MNPE <italic>hla</italic>KO formed biofilms. The latter strains were also less cytotoxic than wild-type MNPE. The addition of exogenous, purified α-toxin to MNPE <italic>hla</italic>KO restored the biofilm phenotype. We speculate that α-toxin affects <italic>S. aureus</italic> phenotypic growth on vaginal mucosa by promoting tissue disruption and biofilm formation. Further, α-toxin mutants (<italic>hla</italic><sup>−</sup>) are not benign colonizers, but rather form a different type of infection, which we have termed high density pathogenic variants (HDPV).</p>