High Genetic Variability of the agr Locus in Staphylococcus Species

Abstract

The agr quorum-sensing and signal transduction system was initially described in Staphylococcus aureus, where four distinct allelic variants have been sequenced. Western blotting suggests the presence of homologous loci in many other staphylococci, and this has been confirmed for S. epidermidis and S. lugdunensis. In this study we isolated agr-like loci from a range of staphylococci by using PCR amplification from primers common to the six published agr sequences and bracketing the most variable region, associated with quorum-sensing specificity. Positive amplifications were obtained from 14 of 34 staphylococcal species or subspecies tested. Sequences of the amplicons identified 24 distinct variants which exhibited extensive sequence divergence with only 10% of the nucleotides absolutely conserved on multiple alignment. This variability involved all three open reading frames involved in quorum sensing and signal transduction. However, these variants retained several protein signatures, including the conserved cysteine residue of the autoinducing peptide, with the exception of S. intermedius of pigeon origin, which contained a serine in place of cysteine at this position. We discuss hypotheses on the mode of action and the molecular evolution of the agr locus based on comparisons between the newly determined sequences.

Genetic polymorphism of the accessory gene regulator (agr) locus in Staphylococcus epidermidis and its association with pathogenicity

“…In our study, we found agr mutations and three agr groups of S. epidermidis. Similar to the findings of Dufour et al (2002), most pathogenic S. epidermidis isolates were in agr group I. Pathogenic S. epidermidis isolates comprised 68 . 2 % group I, 19 .…”

“…The agr locus in staphylococci has been shown to be polymorphic (Moore & Lindsay, 2001;Dufour et al, 2002; Jarraud et al, 2000Jarraud et al, , 2002. The agr locus in S. aureus can be divided into four distinct genetic groups.…”

“…Jarraud et al (2000Jarraud et al ( , 2002 reported that S. aureus agr groups were associated with the pattern of S. aureus diseases. As far as S. epidermidis is concerned, Dufour et al (2002) recently used sequencing to determine (based on a limited number of S. epidermidis strains) that S. epidermidis has three agr groups. Similar to S. aureus agr, sequence variation of S. epidermidis is particularly marked in agrD, the C-terminal two-thirds of agrB and the N-terminal half of agrC.…”

“…About a quarter of S. aureus clinical isolates are naturally occurring agr mutants, most of which show increased ability to attach to polystyrene compared with agr þ strains (Vuong & Otto, 2002). This mechanism probably also occurs in agr mutants of S. epidermidis, but the mutation rate of agr in S. epidermidis is unknown.The agr locus in staphylococci has been shown to be polymorphic (Moore & Lindsay, 2001;Dufour et al, 2002; Jarraud et al, 2000Jarraud et al, , 2002. The agr locus in S. aureus can be divided into four distinct genetic groups.…”

Staphylococcus simiae sp. nov., isolated from South American squirrel monkeys

“…All of these assays, e.g. amplification of the thermonuclease (nuc) gene (Chesneau et al, 1993), the Sa826 bp fragment (Štěpán et al, 2001), the coagulase (coa) gene (Schmitz et al, 1997), the femA regulator gene (Vannuffel et al, 1995) and the accessory gene regulator (agr Sa ) locus (Dufour et al, 2002), gave negative results.The DNA-DNA hybridization experiments and analysis of the DNA G+C content were performed as described by Mannerová et al (2003). On the basis of the results obtained, the novel strains could not be assigned to any of the known staphylococcal species and therefore a polyphasic taxonomic approach was used for their analysis.…”