Comparison of in vitro and in vivo systems to study ica-independent Staphylococcus aureus biofilms

Abstract

The ability of Staphylococcus aureus to form biofilms is considered an important factor in the pathogenesis of central venous catheter-related bacteremia and infections associated with the use of medical prostheses. Different methods have been described for assessing staphylococcal biofilms, but few comparative studies have been attempted to evaluate these techniques; especially related to ica-independent biofilm formation/accumulation. In this study we compared some in vitro and in vivo techniques to evaluate ica-independent biofilms produced by methicillin-resistant S. aureus. We observed that biofilms formed on human fibronectin-covered surfaces were about three times higher than those produced on inert polystyrene surfaces. However, despite the difference in absolute values, a linear correlation was detected between these two models. We also found that biofilms formed on polystyrene or polyurethane surfaces treated with human serum were easily detachable during washing and staining processes. The mouse model of subcutaneous foreign body showed good correlation with the in vitro techniques using either inert polystyrene or solid-phase fibronectin. Thus, our data showed that the microtiter-plate-based spectrophotometric assay is an appropriate method for preliminary biofilm investigations, mainly when a large number of isolates, mutants or systems need to be tested.

A Combined Pharmacodynamic Quantitative and Qualitative Model Reveals the Potent Activity of Daptomycin and Delafloxacin against Staphylococcus aureus Biofilms

“…This is coherent with data in the literature suggesting that S. aureus biofilm formation is favored on plastic surfaces (42,43). Nevertheless, microtiter plate-based models similar to the one used here have demonstrated good correlation with respect to biofilm formation with subcutaneous foreign body infections (38), underlining the potential clinical relevance of the model we developed. In addition, our data are consistent with previous studies evaluating these methods for quantifying biofilm formation or drug effects (14,15,17,19,23,37).…”

“…Similar incubation times were also used in many other studies and considered to generate, respectively, a nascent biofilm related to attachment to the support (31-33) and a mature biofilm (6,15,(34)(35)(36)(37). Of note, in vitro biofilm formation appears highly dependent on the support (38,39) and on the medium (40, 41) used, making direct comparisons between models difficult. In particular, we show here that antibiotics seem more active when a biofilm is grown on a glass support (as used for confocal microscopy experiments) than in polypropylene 96-well plates.…”

Complete Genome Sequence of the MRSA Isolate HC1335 from ST239 Lineage Displaying a Truncated AgrC Histidine Kinase Receptor

“…Real time quantitative reverse transcription polymerase chain reaction (real time qRT-PCR) was performed using the Power SYBRW Green RNA-to-CT TM 1-Step Kit (Applied Biosystems, Foster City, CA, USA) as recommended, and the amount of transcripts were estimated by the Ct comparative method. The primers used for agr -RNAIII and 16S rRNA (endogenous control) were described previously (Ferreira et al 2012). The run was performed in a Step OneTM Real Time PCR System (Applied Biosystems) and analyzed using the Step One Software 2.2 (Applied Biosystems).…”

“…However, the factors involved in the predominance of a MRSA clone over another remains unclear (Figueiredo and Ferreira 2014). The accessory gene regulator (Agr) is the main S. aureus quorum-sensing system in the control of assorted virulence factors and key mechanisms associated with the pathogenesis of S. aureus infections, including biofilm development (Novick et al 2000; Ferreira et al 2012). …”

“…Despite the importance of Agr in the pathogenesis of staphylococcal diseases, isolates lacking detectable Agr activity have also been collected from cases of S. aureus bacteremia (Fowler et al 2004; Traber et al 2008; Shopsin et al 2010; Butterfield et al 2011; Ferreira et al 2012). Indeed, agr -defective S. aureus are more likely to cause persistent infections than the agr -functional isolates, resulting in increased rate of secondary infections and mortality (Fowler et al 2004; Traber et al 2008; Valour et al 2015).…”