Staphylococcus aureus infection of the rabbit cornea following topical administration.
OBJECTIVE
To determine the ability of diverse S. aureus strains to infect the rabbit cornea following topical inoculation, with special emphasis on a strain of unusual virulence.


METHODS
S. aureus strains (5 × 10(5) colony forming units; CFU) were topically applied onto scarified rabbit corneas or 100 CFU were intrastromally injected into rabbit corneas. Eyes were scored by slit lamp examination (SLE) and corneas were cultured to determine the log CFU. Polymorphonuclear leukocytes (PMN) were quantified by myeloperoxidase assays and corneas underwent histopathological analysis. Hemolysin titers of S. aureus strains were determined and S. aureus interactions with rabbit tears or human corneal epithelial cells were investigated.


RESULTS
All strains injected into the cornea produced high SLE scores and multi-log increases in CFU. Following topical inoculation, four strains produced low SLE scores with no bacterial replication. One strain (UMCR1) topically infected the cornea, causing high SLE scores, extensive PMN infiltration, and multi-log increases in CFU. Histopathologic analysis demonstrated a PMN influx into the UMCR1-infected cornea, destruction of the corneal epithelium, and severe edema. Strain UMCR1 did not demonstrate a high hemolysin titer or resistance to the bactericidal activity of rabbit tears, but did invade human corneal epithelial cells with relatively high efficiency.


CONCLUSIONS
One S. aureus strain demonstrated the ability to topically infect the rabbit cornea. This strain was previously found to be unique in its ability to infect the anterior chamber and conjunctiva, suggesting that a key mechanism may be employed to overcome the host defenses of these three ocular sites.
Department of Microbiology, University of Mississippi Medical Center, Jackson, MS 39216, USA.
Aihua
A
Tang
Charles L
CL
Balzli
Armando R
AR
Caballero
Clare C
CC
McCormick
Sidney D
SD
Taylor
Richard J
RJ
O'Callaghan
D000287:Administration, Topical; D000818:Animals; D015169:Colony Count, Microbial; D003319:Corneal Stroma / Q000382:microbiology; D003320:Corneal Ulcer / Q000382:microbiology* / Q000473:pathology; D004195:Disease Models, Animal; D015818:Eye Infections, Bacterial / Q000382:microbiology* / Q000473:pathology; D007154:Immune System Diseases; D007960:Leukocyte Disorders; D009504:Neutrophils / Q000201:enzymology; D009195:Peroxidase / Q000378:metabolism; D011817:Rabbits; D013203:Staphylococcal Infections / Q000382:microbiology* / Q000473:pathology; D013211:Staphylococcus aureus / Q000472:pathogenicity*; D014774:Virulence
D009195:Peroxidase