title: Virulence of protein A-deficient and alpha-toxin-deficient mutants of Staphylococcus aureus isolated by allele replacement.
abstract: The gene coding for protein A (spa) of Staphylococcus aureus 8325-4 has been inactivated by substituting part of the spa coding sequence for a DNA fragment specifying resistance to ethidium bromide. The in vitro-constructed spa::EtBrr substitution mutation was introduced into the S. aureus chromosome by recombinational allele replacement. Southern blot hybridization showed that the in vitro-constructed mutation was present in the chromosomal spa locus. We have previously reported the inactivation of the alpha-toxin gene (hly) by allele replacement with an in vitro-constructed hly::Emr (erythromycin resistance) mutation (M. O'Reilly, J.C.S. de Azavedo, S. Kennedy, and T.J. Foster, Microb. Pathogen. 1:125-138, 1986). A double Spa- Hly- mutant was constructed by transduction. The virulence of Spa- and Hly- mutants was tested by experimental infection of mice. When subcutaneous injections were given, Hly- mutants formed a flat, darkened lesion, whereas Hly+ strains caused a raised, cream lesion. Alpha-toxin was shown to be a major factor in forming subcutaneous lesions and in causing the death of mice injected intraperitoneally. Spa- mutants were slightly less virulent than their Spa+ counterparts, which suggests that protein A is also a virulence factor of S. aureus.
authors: Microbiology Department, Moyne Institute, Dublin, Ireland.
authors: A H
authors: AH
authors: Patel
authors: P
authors: P
authors: Nowlan
authors: E D
authors: ED
authors: Weavers
authors: T
authors: T
authors: Foster
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000172:deficiency*; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D004252:DNA Mutational Analysis; D004269:DNA, Bacterial / Q000235:genetics; D004352:Drug Resistance, Microbial; D004996:Ethidium / Q000494:pharmacology; D006460:Hemolysin Proteins; D051379:Mice; D012871:Skin Diseases / Q000382:microbiology / Q000473:pathology; D013203:Staphylococcal Infections / Q000382:microbiology* / Q000473:pathology; D013205:Staphylococcal Protein A / Q000172:deficiency* / Q000235:genetics; D013211:Staphylococcus aureus / Q000235:genetics / Q000472:pathogenicity*
chemical_list: D001427:Bacterial Toxins; D004269:DNA, Bacterial; D006460:Hemolysin Proteins; D013205:Staphylococcal Protein A; C021091:staphylococcal alpha-toxin; D004996:Ethidium