Abstract
Characteristics of Staphylococcus aureus infections include biofilm formation, leading to the spread of bacteria to the bloodstream causing sepsis and metastatic infections. In particular, in methicillin-resistant S. aureus (MRSA) infections, biofilm formation critically hampers treatment and causes poor prognosis. We explored the biofilm formation of MRSA in the presence or absence of plasma and compared morphological characteristics, accumulation of antibiotics, and resistance to bactericidal activity, using continuous optimizing confocal reflection microscopy. Addition of plasma significantly increased biofilm formation, which is characterized by an uneven surface and aggregation of bacteria (hereafter plasma biofilm). The flow-cell system, which enabled a continuous supply of plasma, accelerated biofilm formation in both the tested strains of MRSA (BAA1556 and N315). Accumulation of green fluorescence-labeled vancomycin was observed within 5 minutes in the plasma-free biofilm, but not in the plasma biofilm. Delay of accumulation was also observed for daptomycin in plasma biofilm. Plasma biofilm bacteria were more resistant to anti-MRSA antibiotics than plasma-free biofilm bacteria. These data demonstrate that the plasma biofilm of S. aureus is substantially different from the plasma-free biofilm. Plasma biofilm, especially in the flow-cell system, could be a clinically relevant model to analyze MRSA infections and treatment.
Highlights
Staphylococcus aureus is a gram-positive coccus that colonizes the nasal mucosa and skin of healthy individuals.[1]
confocal reflection microscopy (COCRM) method was, for the first time, applied for the observation of S. aureus biofilm, which showed the rapid growth of biofilms in the presence of plasma
Delayed antibiotic penetration or accumulation and resistance to the bactericidal activity of anti-methicillin-resistant S. aureus (MRSA) agents were observed in the plasma biofilms
Summary
Staphylococcus aureus is a gram-positive coccus that colonizes the nasal mucosa and skin of healthy individuals.[1] This organism can cause a wide range of diseases from skin or soft tissue infections to systemic and fatal diseases.[1,2,3] In particular, methicillin-resistant S. aureus (MRSA) is a hazardous organism because of its resistance to multiple antibiotics and biofilm formation ability. The appearance of community-acquired MRSA (CA-MRSA), in addition to the conventional hospitalacquired MRSA (HA-MRSA), poses a high risk to immune compromised patients and healthy individuals. It is well known that biofilm-forming bacteria can survive in the presence of high concentrations of antimicrobial agents.[4] Bacterial biofilms consist of a variety of components and substances from both the bacteria (polysaccharide, peptidoglycan, and DNA) and the host (cell debris, coagulation products, and DNA). Biofilm composition varies depending on the causative organism and/or host factors
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