Differences in virulence between two Candida albicans strains in experimental keratitis.
OBJECTIVE
To study the differences in disease caused by two wild-type strains of Candida albicans in a model of contact lens-facilitated keratitis in rabbits.


METHODS
Two strains, SC5314 and VE175, were examined. Standardized inocula were placed on the debrided corneal surface of one eye in Dutch belted rabbits and covered with a contact lens. A temporary tarsorrhaphy was opened after 24 hours with removal of the contact lens. Six days later, corneas were photographed and animals killed. Corneas were bisected with one half for quantitative isolate recovery and the other for stromal penetration by hyphae.


RESULTS
Strain SC5314 was significantly more virulent. The mean hyphal penetration into the cornea was 24.4% +/- 8.5% of the corneal thickness, and in three of six corneas hyphae penetrated through the entire cornea. In contrast, for VE175, the mean hyphal penetration was 2.6% +/- 1.2%. The difference between these two strains was statistically significant (P = 0.0297). Hyphae did not penetrate into the deep layers of the cornea in any of the six rabbits infected with VE175. The grading of clinical disease was consistent with histology, in that strain SC5314 caused more severe infection than VE175 and the difference was statistically significant (P = 0.0048). There was no difference in isolate recovery.


CONCLUSIONS
Wild-type strains of C. albicans can differ significantly in virulence as measured by depth of fungal invasion into corneas and clinical evaluation of infection. Further characterization of the intrinsic genetic differences between such strains may help identify factors responsible for fungal virulence.
O'Day
D M
DM
Department of Ophthalmology and Visual Sciences, Vanderbilt University Medical School, Nashville, Tennessee 37232-8808, USA. denis.m.o'day@mcmail.vanderbilt.edu
Head
W S
WS
Csank
C
C
Shetlar
D J
DJ
Robinson
R D
RD
McCollum
G W
GW
Yang
R
R
Zhu
T L
TL
Wang
M X
MX
D000818:Animals; D002176:Candida albicans / Q000302:isolation & purification / Q000472:pathogenicity*; D002177:Candidiasis / Q000382:microbiology* / Q000473:pathology; D003315:Cornea / Q000382:microbiology* / Q000473:pathology; D003320:Corneal Ulcer / Q000382:microbiology* / Q000473:pathology; D015821:Eye Infections, Fungal / Q000382:microbiology* / Q000473:pathology; D005260:Female; D008297:Male; D011817:Rabbits; D014774:Virulence