Identification of a distinctive phenotype for endocarditis-associated clonal complex 22 MRSA isolates with reduced vancomycin susceptibility

Abstract

Purpose. We previously identified an association between CC22 meticillin-resistant Staphylococcus aureus (MRSA) bloodstream infection isolates with an elevated vancomycin MIC (V-MIC) in the susceptible range (1.5-2 mg l À1 ) and endocarditis. This study explores whether these isolates have a specific phenotype consistent with the clinical findings.Methodology. CC22 and CC30 MRSA isolates with high (1.5-2 mg l À1 ) and low ( 0.5 mg l À1 ) V-MICs were tested for fibrinogen and fibronectin binding, virulence in a Galleria mellonella caterpillar model, phenol soluble modulin production and accessory gene regulator (agr) expression.Results. CC22 high V-MIC, but not CC30 high V-MIC isolates, showed sustained fibrinogen binding through a stationary growth phase and increased PSM production, specifically PSMa1, compared with respective low V-MIC isolates. Expression was lower in both CC22 and CC30 high V-MIC isolates compared with respective low V-MIC isolates, although there was no associated reduction in virulence in the caterpillar model. Conclusions.The identification of a distinct phenotype for CC22 high V-MIC isolates supports the hypothesis that bacterial factors contribute to the mechanism underlying their association with endocarditis. Further study of these isolates could shed light on the molecular mechanism of endocarditis in humans.

Antimicrobial activity of apple cider vinegar against Escherichia coli, Staphylococcus aureus and Candida albicans; downregulating cytokine and microbial protein expression

“…The anti-microbial agents used to treat gram negative infections such as β-lactams, fluroquinolones, sulfamethaoxathoxazole and trimethroprin are becoming increasingly ineffective. Strains of S. aureus have emerged with reduced susceptibility to vancomycin and methicillin 6 , 11 , 12 . Furthermore, antibiotic action itself can be problematic in terms of cell membrane permeability, intracellular inactivation and the inability to reach intracellular structures in which organisms can hide.…”

Tolerance of MRSA ST239-TW to chlorhexidine-based decolonization: Evidence for keratinocyte invasion as a mechanism of biocide evasion

“…S. aureus 8325-4 (fibronectin binding) or S. aureus Newman (fibrinogen binding) were included as binding controls. 42…”