Impact of individual extracellular proteases on Staphylococcus aureus biofilm formation in diverse clinical isolates and their isogenic sarA mutants.
Bottom Line: These results confirm an important role for multiple extracellular proteases in S. aureus pathogenesis and the importance of sarA in repressing their production.Moreover, purified aureolysin limited biofilm formation in 14 of 15 methicillin-resistant isolates and 11 of 15 methicillin-susceptible isolates, while dispersin B had little impact in UAMS-1, LAC, or 29 of 30 contemporary isolates of S. aureus.This suggests that the role of sarA and its impact on protease production is important in diverse strains of S. aureus irrespective of their methicillin resistance status.
Affiliation: Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, Arkansas.Show MeSH
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Mentions: The hypothesis that multiple proteases are involved is consistent with the observations that individual proteases exhibit differential specificity with respect to S. aureus targets previously implicated in biofilm formation (Beenken et al. 2014; Mrak et al.,2012; Zielinska et al. 2011, 2012). However, all of the results discussed above are based on in vitro experiments, leaving open the possibility that they do not accurately reflect in vivo relevance. To address this possibility, we used our murine bacteremia model to examine the impact of eliminating the production of individual proteases in an FPR3757 sarA mutant under in vivo conditions, with LAC, its sarA mutant, and its sarA mutant unable to produce any extracellular protease being included as controls (Zielinska et al. 2012). The results confirmed that mutation of sarA attenuates the virulence of both LAC and FPR3757 as assessed by weight loss and bacterial burdens in the kidney, spleen, and heart (Fig. 7). They also confirmed that eliminating the ability of a LAC sarA mutant to produce all extracellular proteases reversed this effect. In contrast, eliminating the ability of an FPR3757 sarA mutant to produce individual proteases, or in the case of sspAB and splA-F, multiple proteases encoded within the same operon, had no statistically significant effect. Presumably, this is a reflection of the aforementioned differential specificity of these proteases and its impact on the ability of S. aureus to produce multiple virulence factors that contribute to its pathogenesis.
Affiliation: Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, Arkansas.