agr RNAIII divergently regulates glucose-induced biofilm formation in clinical isolates of Staphylococcus aureus

Abstract

Staphylococcus aureus is an important nosocomial and community-acquired pathogen. Hospital infections are frequently complicated by the ability of bacteria to form biofilms on different surfaces. The development of bacterial films on medical indwelling devices, such as prostheses, often requires surgical procedures to remove the contaminated implant. Indeed, biofilm formation on central endovenous catheters is a major cause of primary bacteraemia in hospitals. The modulation of virulence factors in S. aureus is orchestrated by a number of global regulators including agr RNAIII. To improve our understanding of the role of the agr quorum-sensing system in biofilm formation by S. aureus, we constructed a number of agr-null mutants, derived from contemporary clinical isolates. Analysis of these mutants indicates that agr has a significant impact on biofilm development for most of the isolates tested. Our data show that RNAIII can control both biofilm formation and accumulation. The agr effect included both up-and downregulation of biofilms, even for isolates within the same lineage, corroborating the hypothesis that the mechanisms involved in S. aureus biofilms are complex and probably multifactorial.

A novel role for SarX in Staphylococcus epidermidis biofilm regulation

“…The S. aureus SarX protein has been implicated in the regulation of the agr system (Manna & Cheung, 2006), which is known to regulate biofilms in a strain-dependent manner (Beenken et al, 2003(Beenken et al, , 2010Boles & Horswill, 2008;Coelho et al, 2008;O'Neill et al, 2007;Regassa et al, 1992;Vuong et al, 2000aVuong et al, , b, 2003Vuong et al, , 2004. Here, real-time RT-PCR was employed to compare RNAIII transcription in overnight BHI glucose cultures of CSF41498 pLI50, CSF41498 pSESAX6, SARX1 pLI50 and SARX1 pSESAX6.…”

“…The accessory gene regulator (agr) system controls quorum sensing, and is known to influence the biofilm phenotype of staphylococci in a strain-dependent manner (Beenken et al, 2003(Beenken et al, , 2010Boles & Horswill, 2008;Coelho et al, 2008;O'Neill et al, 2007;Regassa et al, 1992;Vuong et al, 2000aVuong et al, , b, 2003Vuong et al, , 2004. The agr locus encodes two divergently transcribed mRNA transcripts, RNAII and RNAIII (Morfeldt et al, 1995;Novick & Geisinger, 2008).…”

Characterization of coagulase-negative staphylococci isolated from hospital indoor air and a comparative analysis between airborne and inpatient isolates of Staphylococcus epidermidis

“…Because staphylococcal biofilm is subject to phase variation, tests were repeated four times and at least two independent experiments were carried out for each isolate tested. The isolates were classified as: strong, optical density (OD) ¢0.92; moderate, 0.92.OD¢0.46; weak, 0.46.OD.0.24; and biofilm nonproducer, OD¡0.24, as suggested previously by Coelho et al (2008). For S. epidermidis isolates only, biofilm production was also tested using a Congo red agar test (Freeman et al, 1989).…”

“…Biofilm formation/accumulation was quantified using sterile, flat-bottomed, 96-well Nunclon microtitre plates (Nunc). Biofilm growth was induced with trypticase soy broth supplemented with 1 % (w/v) glucose, and the biofilm was stained with crystal violet and analysed spectrophotometrically, as described by Coelho et al (2008). Because staphylococcal biofilm is subject to phase variation, tests were repeated four times and at least two independent experiments were carried out for each isolate tested.…”

Virulence Factors in Methicillin-Resistant <i>Staphylococcus aureus</i> Isolated from ICU Units in Brazil

“…The mean value was used for the statistical calculation. In addition, to confirm the differences between biofilm phenotypes, as determined by BU values, confocal laser scanning microscopy (CLSM) was used to obtain the structural images of the biofilms [13]. Here, the biofilm assays were performed at the same way, but after being fixed, the bacterial cells were stained with 25 nanomoles (nM) SYTO9 and propidium iodide (Live/Dead Bacteria-Invitrogen) for 15 minutes (min) in the dark.…”