Open AccessVariation in the agr ‐dependent expression of α‐toxin and protein A among clinical isolates of Staphylococcus aureus from patients with septicaemia
Author(s) -
Li S,
Arvidson S,
Möllby R
Publication year - 1997
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1997.tb10422.x
Subject(s) - toxin , staphylococcus aureus , biology , virulence , proteases , microbiology and biotechnology , gene , repressor , locus (genetics) , gene expression , genetics , bacteria , enzyme , biochemistry
In Staphylococcus aureus synthesis of many virulence factors is regulated by the agr locus. The regulatory molecule RNAIII, induced by agr , activates transcription of the α‐toxin gene, hla , while it acts as a repressor of the protein A gene, spa . Forty clinical strains of S. aureus from human blood cultures were analysed for α‐toxin and protein A production. An inverse correlation between α‐toxin and protein A production was found in most strains. The levels of α‐toxin and protein A production varied significantly among strains, which indicates various levels of the regulator, RNAIII. This was confirmed by selecting strains producing different amounts of α‐toxin, showing that the variations in toxin production are due to the variations of RNAIII transcript. However, in one of the selected strains which produced high levels of α‐toxin, OR153, although RNAIII is also strongly expressed, the specific hla mRNA was unexpectedly low. One partial explanation for the high α‐toxin production by this clinical isolate might be its lack of extracellular proteases.