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

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.

Investigation of biofilm production and its association with genetic and phenotypic characteristics of OM (osteomyelitis) and non-OM orthopedic Staphylococcus aureus

“…Although Tang J et al indicated that a single gene or subset of genes cannot be utilized as an indicator of biofilm production [23], In some other studies, traditional adhesion-associated genes including ebps, ica and fnbA were suggested to be positively associated with biofilm production [11,22]. Exotoxin gene lip and hla genes were also verified to contribute to biofilm formation [12,32]. Different from the above results, in this study, we first found that the fib, hlgv and lukED gene was positively correlated, while sei, sem and seo genes were negatively correlated with biofilm production of orthopedic S. aureus strains (Tables 2, and 3).…”

“…In a previous study conducted by our team [9], we collected and characterized the S. aureus isolates obtained from the orthopedic center of our hospital over a 2-year period. In consideration that genetic and phenotypic characteristics of bacteria strains are closely related to the biological and physiological properties [6,8,[11][12][13], we hypothesized that some of these characteristics might be associated with biofilm formation, and the association might be different between OM and non-OM isolates. Therefore, interested isolates from the previous study were included and divided into OM and non-OM isolates, biofilm production was measured using the crystal violet assay.…”

“…In previous studies, it is controversial on the issue of whether virulence genes could be regarded as indicators for biofilm-forming capacity of S. aureus strains [11,12,19,22,23]. To investigate this question among orthopedic S. aureus strains, the carriage of various virulence genes was tested and summarized in Table 2.…”

Structure-based discovery of a small-molecule inhibitor of methicillin-resistant Staphylococcus aureus virulence

“…The elevated expression of a-toxin in the USA300 clone and in historic human epidemic strains correlates with increased pathogenicity in mouse models of skin and soft tissue infection, pneumonia and sepsis (48,49). a-Toxin also plays a role in biofilm formation by clinical MRSA isolates (50). Moreover, LukED relies on the chemokine receptor CCR5 to kill T lymphocytes, macrophages and dendritic cells, as well as CXCR1 and CXCR2 to kill leukocytes (19,51).…”

Structure-Based Discovery of a Novel Small-Molecule Inhibitor of Methicillin-Resistant S. aureus

“…The elevated expression of atoxin in the USA300 clone and in historic human epidemic strains correlates with increased pathogenicity in mouse models of pneumonia and sepsis (Bubeck Wardenburg and Schneewind, 2008;DeLeo et al, 2011). a-Toxin also plays a role in biofilm formation by clinical MRSA isolates (Anderson et al, 2018). Moreover, LukED relies on the chemokine receptor CCR5 to kill T lymphocytes, macrophages and dendritic cells, as well as CXCR1 and CXCR2 to kill leukocytes Reyes-Robles et al, 2013).…”