Corneal virulence of Staphylococcus aureus in an experimental model of keratitis.
The aim of this study was to determine the pathogenic role of alpha-, beta-, and gamma-toxins in a rabbit model of Staphylococcus aureus keratitis. S. aureus strains 8325-4, Newman, and their isogenic mutants were intrastromally injected into rabbit corneas. Eyes were scored for pathology by slit lamp examination (SLE), histologic examination, and bacterial colony-forming units (CFU) per cornea were determined. Rabbits were immunized against alpha-toxin and subsequently challenged with S. aureus strain 8325-4 or Newman. All strains grew equivalently to approximately 7 log CFU/cornea at 25 h postinfection. SLE scores at 15, 20, and 25 h postinfection revealed that alpha-toxin - producing strains caused greater corneal pathology than strains deficient in alpha-toxin. A beta-toxin - deficient mutant produced significantly less ocular edema than its parent or rescued strains. The gamma-toxin-deficient mutant, relative to its parent strain or genetically rescued strain, had reduced virulence. These results demonstrate that the virulence of S. aureus involves mainly alpha-toxin and to a lesser extent gamma-toxin, with beta-toxin mediating minimal corneal pathology.
Dajcs
Joseph J
JJ
Department of Microbiology, Immunology, and Parasitology, LSU Health Sciences Center in New Orleans, New Orleans, Louisiana 70112, USA.
Thibodeaux
Brett A
BA
Girgis
Dalia O
DO
O'Callaghan
Richard J
RJ
D000818:Animals; D001426:Bacterial Proteins; D001427:Bacterial Toxins / Q000235:genetics / Q000276:immunology / Q000633:toxicity; D003315:Cornea / Q000382:microbiology*; D006460:Hemolysin Proteins / Q000276:immunology / Q000633:toxicity; D007634:Keratitis / Q000382:microbiology*; D011817:Rabbits; D013108:Sphingomyelin Phosphodiesterase; D013203:Staphylococcal Infections / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000472:pathogenicity*
D001426:Bacterial Proteins; D001427:Bacterial Toxins; D006460:Hemolysin Proteins; C037956:gamma-hemolysin, Staphylococcus aureus; C021091:staphylococcal alpha-toxin; D013108:Sphingomyelin Phosphodiesterase; C029878:hlb protein, Staphylococcus aureus