In this study we used exotoxin analysis, functional genomics and a murine infection model to investigate the relative contribution of α-hemolysin, α-type phenol

soluble modulins and Selleckchem Gemcitabine Panton-Valentine leukocidin to the enhanced virulence of ST93 CA-MRSA. We show that BIIB057 clinical trial increased virulence in the BALB/c mouse skin infection model is less dependent on α-type phenol soluble modulin or Panton-Valentine leukocidin production but is instead due to high-level expression of α-hemolysin in this clone, controlled predominantly by the agr system. Results and discussion The emergence of CA-MRSA is a major public health issue, and there is a clear need to understand the basis for both virulence and transmission of global clones of CA-MRSA. The genetically distinct CA-MRSA clone ST93-IV [2B] has rapidly become the dominant clone in Australia and its rise accounts for the increase in incidence of CA-MRSA as a whole in this country [13]. We, and others have previously shown that ST93 strain JKD6159 is

the most virulent global clone of S. aureus in murine models [14, 15]. To determine the mediators of virulence in this clone we initially studied exotoxin expression in a large collection of ST93 selleck S. aureus from around Australia, and compared representative high and low expressing strains to an international selection of clones. Exotoxin expression in ST93 CA-MRSA strains Staphylococcus aureus expresses a wide range of exotoxins that may contribute to virulence. Because Hla, PVL and α-type PSMs have been found by others to be important virulence factors

in CA-MRSA strains [9, 11, 16], we measured in vitro expression of these exotoxins by the wildtype ST93 strains and non-ST93 comparator strains. The main isolates used in this study are described in Table  1, while the collection of ST93 isolates from around Australia used for comparative exotoxin expression is from a study by Coombs et al.[17] and summarized in Additional file 1. The comparison of expression of international clones to the ST93 reference strain JKD6159 and three additional ST93 strains selected for genome sequencing (see Vildagliptin below) are shown in Figure  1, while the results for all 59 ST93 isolates compared to USA300 are shown in Additional file 2 (α-type PSMs) and Additional file 3 (Hla). The results of PVL analysis for the ST93 collection has been previously reported [17]. Because PVL is a 2-component exotoxin and both LukS-PV and LukF-PV are required for activity, we chose to measure LukF-PV expression by quantitative Western blot. LukF-PV was chosen over LukS-PV to obtain anti-LukF-PV antibody with increased specificity of binding as there was more sequence divergence between lukF-PV and the orthologous 2-component S. aureus exotoxins compared to lukS-PV. Although there are four α-type PSMs, PSMα3 causes the most significant neutrophil lysis [11] and we measured deformylated and N-formylated PSMα3 expression by high performance liquid chromatography (HPLC).