Alpha-Toxin Contributes to Biofilm Formation among Staphylococcus aureus Wound Isolates.

Michele Anderson,Marnie Peterson,Jisun Sun,Laura Breshears,Heidi Wallis,Christine Tkaczyk,James Johnson,Emily Schaaf,Bret Sellman

doi:10.3390/toxins10040157

Abstract

Biofilms complicate treatment of Staphylococcus aureus (SA) wound infections. Previously, we determined alpha-toxin (AT)-promoted SA biofilm formation on mucosal tissue. Therefore, we evaluated SA wound isolates for AT production and biofilm formation on epithelium and assessed the role of AT in biofilm formation. Thirty-eight wound isolates were molecularly typed by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (ST), and spa typing. We measured biofilm formation of these SA isolates in vitro and ex vivo and quantified ex vivo AT production. We also investigated the effect of an anti-AT monoclonal antibody (MEDI4893*) on ex vivo biofilm formation by methicillin-resistant SA (USA 300 LAC) and tested whether purified AT rescued the biofilm defect of hla mutant SA strains. The predominant PFGE/ST combinations were USA100/ST5 (50%) and USA300/ST8 (33%) for methicillin-resistant SA (MRSA, n = 18), and USA200/ST30 (20%) for methicillin-susceptible SA (MSSA, n = 20). Ex vivo AT production correlated significantly with ex vivo SA wound isolate biofilm formation. Anti-alpha-toxin monoclonal antibody (MEDI4893*) prevented ex vivo biofilm formation by MRSA USA300 strain LAC. Wild-type AT rescued the ex vivo biofilm defect of non-AT producing SA strains. These findings provide evidence that AT plays a role in SA biofilm formation on epithelial surfaces and suggest that neutralization of AT may be useful in preventing and treating SA infections.

Highlights

Biofilms are complex microbial communities embedded in extracellular matrix that are resistant to antimicrobial treatment and host immune responses [1]
We described the development of this this method and determined the kinetics studies, we described the development of method and determined the kinetics of of methicillin-susceptibleS.S. aureus aureus (MSSA)
To understand why more exogenous AT is needed to support biofilm formation than what we can recover from tissue infected with AT-producing strains, we investigated the proportion of exogenous AT recoverable from porcine vaginal mucosa (PVM)

Summary

Introduction

Biofilms are complex microbial communities embedded in extracellular matrix that are resistant to antimicrobial treatment and host immune responses [1]. Several studies have confirmed the presence of biofilms that contain Staphylococcus aureus (SA) in wounds and skin and soft tissue infections (SSTIs) [2,3,4]. SA clonal background, virulence factor production, and biofilm formation are currently unknown for SA wound isolates. The heightened virulence of community-associated MRSA USA300 in experimental models has been associated with the production of alpha-toxin (AT), a 33 kDa pore-forming, cytolytic exotoxin [9]. Alpha-toxin is expressed by most MSSA and MRSA isolates. A study of 994 respiratory SA isolates from 34 countries determined that the AT gene, hla, was present and Hla expressed by 99% of MSSA and 83.2% of MRSA isolates regardless of geographic region [14]

Methods

Results

Conclusion