Human plasma enhances the expression of Staphylococcal microbial surface components recognizing adhesive matrix molecules promoting biofilm formation and increases antimicrobial tolerance In Vitro

Abstract

BackgroundMicrobial biofilms have been associated with the development of chronic human infections and represent a clinical challenge given their increased antimicrobial tolerance. Staphylococcus aureus is a major human pathogen causing a diverse range of diseases, of which biofilms are often involved. Staphylococcal attachment and the formation of biofilms have been shown to be facilitated by host factors that accumulate on surfaces. To better understand how host factors enhance staphylococcal biofilm formation, we evaluated the effect of whole human plasma on biofilm formation in clinical isolates of S. aureus and the expression of seven microbial surface components recognizing adhesive matrix molecules (MSCRAMMs) known to be involved in biofilm formation by quantitative real-time PCR. We also evaluated whether plasma augmented changes in S. aureus biofilm morphology and antimicrobial resistance.ResultsExposure of clinical isolates of S. aureus to human plasma (10%) within media, and to a lesser extent when coated onto plates, significantly enhanced biofilm formation in all of the clinical isolates tested. Compared to biofilms grown under non-supplemented conditions, plasma-augmented biofilms displayed significant changes in both the biofilm phenotype and cell morphology as determined by confocal scanning laser microscopy (CLSM) and scanning electron microscopy (SEM), respectively. Exposure of bacteria to plasma resulted in a significant fold-increase in MSCRAMM expression in both a time and isolate-dependent manner. Additionally, plasma-augmented biofilms displayed an increased tolerance to vancomycin compared to biofilms grown in non-supplemented media.ConclusionsCollectively, these studies support previous findings demonstrating a role for host factors in biofilm formation and provide further insight into how plasma, a preferred growth medium for staphylococcal biofilm formation enhances as well as augments other intrinsic properties of S. aureus biofilms. Consequently, these findings indicate that incorporation of host factors may be necessary to better replicate in vivo conditions and for the best utility of a clinical biofilm assay to evaluate the process of biofilm formation and treatments.

Rifamycin Derivatives Are Effective Against Staphylococcal Biofilms In Vitro and Elutable From PMMA

“…First, the in vitro model used for biofilm development and susceptibility testing cannot adequately recapitulate biofilms developed in vivo, in which host factors absent under Table 1. Activity of Rifamycin Derivatives on Biofilms in vitro culture conditions could influence the biofilm phenotype and possibly affect antimicrobial activities observed herein [10]. However, the biofilm model used in this study is well characterized and has been demonstrated to be a reliable, reproducible experimental tool for evaluating susceptibilities of bacterial biofilms to various agents [3,11,13].…”

Activity of Norspermidine on Bacterial Biofilms of Multidrug-Resistant Clinical Isolates Associated with Persistent Extremity Wound Infections

“…Briefly, biofilms were grown as described above using glass chamber slides, as previously described (Cardile et al 2014). Following overnight treatment (inhibition or dispersal), biofilms were gently washed with sterile PBS, fixed for 10 min at room temperature with 4% paraformaldehyde in PBS, and stained using Film Tracer™ SYPRO ® Ruby Biofilm Matrix Stain, according to the manufacturer's instructions (Molecular Probes, Eugene, OR).…”

“…To evaluate the effect of norspermidine on the expression of genes related to homoserine lactone synthesis (A1S_0109 - A1S_0114) in A. baumannii , including a reference strain ATCC 17978 as well as three representative clinical isolates, biofilms were formed in 6-well tissue culture plates using previously described methods in the presence of 5 and 20 mM norspermidine (in 100mM HEPES) for 24 h at 37°C (Cardile et al 2014; Malachowa et al 2011). Following overnight incubation, supernatants were removed, individual wells were gently washed with PBS and attached bacteria (i.e.…”

The Staphylococcal Biofilm: Adhesins, Regulation, and Host Response

“…The Staphylococcal MSCRAMMs are the Clf-Sdr family proteins, including Bbp (bone sialoprotein-bnding protein), the FnBPs (fibronectin-binding proteins), and CNA (collagen adhesion). Exposure of S. aureus to human plasma in vitro enhances both MSCRAMM expression and biofilm formation, suggesting the importance of their role in in vivo biofilm infections (43). …”