Indeed, USA400 was the far most common CA-MRSA clone recovered from three northern remote communities of Saskatchewan,

Canada [11]. In 2005, a novel variant of the lineage ST1-SCCmecIV emerged in Rio de Janeiro city as an important cause of bloodstream infections (BSI) [12]. It is intriguing that ICG-001 ic50 Despite the genetic relationship with Australian WA-1 and MW2/USA400, isolates of this novel clone were PVL-negative, multiresistant and mostly involved in hospital-associated BSI [12]. It is still poorly understood why isolates of CA-MRSA have become successful so quickly [13]. Nevertheless, for hospital-associated R788 MRSA (HA-MRSA), the bacterial ability to produce biofilm has been recognized as an important virulence factor for the pathogenesis of intravenous catheter-related bacteremia and infections associated with the use of medical prosthesis. In addition, the bacterial ability to adhere to, colonize and invade host tissues is considered important factor associated with bacterial virulence, adaptation and spread

[14, 15]. Different surface proteins have been implicated in biofilm formation/accumulation and host colonization, including fibronectin-binding ABT-888 in vivo proteins A and B (FnBPAB), S. aureus surface protein G (SasG) and staphylococcal protein A (Spa) [16–19]. In addition, extracellular DNA (eDNA) has also been associated with bacterial biofilms [20]. It is also well known that virulence in S. aureus is modulated by an intricate regulatory network [21]. The accessory gene regulator (agr), the major S. aureus quorum sensing system, down-regulates a number of genes encoding for cell-surface proteins involved in colonization processes, and up-regulates (by an indirect mechanism involving RNAIII dependent down-regulation of Rot) different exoproteins

associated with host-cell damages [22]. Previous works have suggested that inactivation of Agr could be very effective at inhibiting S. aureus infections [23], including those associated with implantable medical devices [24, 25]. Studies have demonstrated that biofilm production, host cell adhesion and invasion as well as other mechanisms involved in the establishment and course of staphylococcal diseases were affected by knockout of the agr locus [26–28]. Despite the improvements Clomifene achieved in staphylococcal virulence, most of the investigations have been carried out using relatively few laboratory constructions or clinical isolates [28]. In addition, those results have not been validated using current clinical isolates of MRSA. In this paper we characterized the biofilm formed by USA400-related (ST1-SCCmecIV) MRSA emergent in Rio de Janeiro, investigated the adhesive and invasive properties of naturally agr-dysfunctional isolates and analyzed the impact of the agr inhibition on S. aureus infections associated with the use of medical device.