Associations between enterotoxin gene cluster types egc1, egc2 and egc3, agr types, enterotoxin and enterotoxin-like gene profiles, and molecular typing characteristics of human nasal carriage and animal isolates of Staphylococcus aureus

Abstract

Twenty genes encoding enterotoxin and enterotoxin-like proteins have been described in Staphylococcus aureus strains. Five of these occur commonly in the enterotoxin gene cluster (egc: selo, selm, sei, seln and seg). In the sei-seln intergenic region, two pseudogenes, yent1 and yent2, can be present or an additional gene designated selu or a variant selu v . Whilst frequencies of loci bearing pseudogenes (egc1) or the selu gene (egc2) have been reported, the distinction between selu-bearing and selu v -bearing (egc3) loci has rarely been made. A PCR-RFLP procedure involving cleavage of the sei-seln intergenic region by restriction endonuclease BbvI or TseI was developed that allowed differentiation of selu + and selu v + loci. In addition, PCR primers were designed to yield a 203 bp amplimer for sequencing of a selu or selu v intragenic region, which encompassed ten signature nucleotide differences. A total of 43 egc + human nasal isolates and 53 egc + bovine, ovine, caprine, leporine and gallinaceous isolates were egc typed and agr typed. None of the animal isolates was of agr type III. A total of 12 out of 17 egc3 + human nasal isolates were of agr type III, the other 5 being agr type I. On the basis of representative multilocus sequence typing, agr type III/egc3 + strains belonged to CC30. Human nasal isolates bearing an egc1 locus were distributed evenly across agr types I, II and III. Only two nasal isolates had an egc2 locus. All 14 agr type IV isolates, only 1 of which was of human origin, possessed an egc2 locus. The agr IV nasal isolate was fusidic acid sensitive and was found to be ST123 (CC121). There were strong associations between bovine, leporine and gallinaceous S. aureus clonal types and egc locus types. The PCR-RFLP procedure was used to screen an additional 45 S. aureus isolates from dogs, cats, rats, pigs and horses for egc locus types. Of these, 33 were egc " . Six equine isolates were selu + . One canine and three porcine isolates possessed pseudogenes yent1 and yent2. One porcine and one canine isolate each had the selu v gene. Putative relationships between disease-causing propensity and egc type need (re-)evaluation.

Population structure and exotoxin gene content of methicillin-susceptible Staphylococcus aureus from Spanish healthy carriers

“…However, some already described exceptions were also found (CC1-agrIII, CC25-agrIV, CC30-agrI, CC59-agrIV [53e55]). Individual exotoxin genes and some groups of genes are carried by well-known mobile genetic elements, but new gene arrangements can arise through deletion or recombination [32,56,57]. This is particularly true in the case of nSab, the genomic island where the egc1 and egc2 clusters have been located [21].…”

Superantigens in Staphylococcus aureus isolated from prosthetic joint infection

“…The most common SAg gene combination was seg and sei , which coexist in enterotoxin gene cluster ( egc ) (Jarraud, et al, 2001). egc normally includes seg , sei , sem , sen , and seo together, but they are not always present due to egc polymorphisms (Blaiotta, Fusco, von Eiff, Villani, & Becker, 2006) and varying egc types (Collery, Smyth, Tumilty, Twohig, & Smyth, 2009). …”

Unveiling Staphylococcus aureus enterotoxin production in dairy products: a review of recent advances to face new challenges

“…SE genes are found in various genetic supports and all these supports are mobile genetic elements (Le Loir et al 2003). SE genes can be carried by plasmids (seb, sed, sej, ser, ses and set) (Bayles and Iandolo 1989;Omoe et al 2003;Ono et al 2008;Shalita et al 1977;Zhang et al 1998), by phages (temperate for sea, defective for see, selk, selp and selq) (Betley and Mekalanos 1988;Coleman et al 1989;Couch et al 1988;Goerke et al 2009), on pathogenicity islands (SaPI) (seb, sec, selk, sell and selq) (Novick and Subedi 2007) or genomic islands (seg, seh, seli, selk, sell, selm, seln, selo, selp, selq, selu and selv) (Baba et al 2008;Collery et al 2009;Holden et al 2004;Jarraud et al 2001;Letertre et al 2003;Thomas et al 2006). Some of them have been found in several genetic elements such as seb which was reported to be located on the chromosome, a plasmid or a transposon (Altboum et al 1985;Shafer and Iandolo 1978;Shalita et al 1977) and sec, on a plasmid or a pathogenicity island (Altboum et al 1985;Fitzgerald et al 2001).…”