title: Expression of an iron-regulated hemolysin by Edwardsiella tarda.
abstract: The ability of Edwardsiella tarda to hemolyse red blood cells was investigated. Most E. tarda strains (> 80%) produced a hemolysin when assayed by either an agar overlay or contact-dependent hemolysis technique. This activity was cell-associated (CAH) and not released into the culture supernatant under routine conditions. When quantified, E. tarda strains significantly produced 30-40-fold higher levels of hemolytic activity against guinea pig, sheep, or rabbit erythrocytes than either E. hoshinae or E. ictaluri. When grown under iron restricted-conditions in the presence of ethylenediamine di(o-hydroxyphenylacetic acid), hemoglobin, hematin and hemin were found to stimulate growth in both liquid and agar bioassays. Hemolysin activity could be released from selected E. tarda strains when grown in L broth supplemented with EDDA; hemolytic activity was 3- to > 40-fold under these conditions when compared to L broth alone. Preliminary characterization of the hemolysin of strain ET-13 indicates that it is a heat-labile protein with active sulphydryl and thiol groups. These results indicate that, in addition to its invasive capabilities, E. tarda produces a hemolysin which is at least partially regulated by the relative availability of iron and may play a role in human disease.
authors.affiliation: Microbial Diseases Laboratory, California Department of Health Services, Berkeley 94704-1011.
authors.forename: J M
authors.initials: JM
authors.lastname: Janda
authors.forename: S L
authors.initials: SL
authors.lastname: Abbott
mesh_terms: D003470:Culture Media; D004755:Enterobacteriaceae / Q000254:growth & development / Q000378:metabolism* / Q000472:pathogenicity; D004756:Enterobacteriaceae Infections / Q000209:etiology; D006460:Hemolysin Proteins / Q000378:metabolism*; D006461:Hemolysis; D006801:Humans; D066298:In Vitro Techniques; D007501:Iron / Q000378:metabolism*; D014774:Virulence
chemical_list: D003470:Culture Media; D006460:Hemolysin Proteins; D007501:Iron