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Infection and Immunity, July 1999, p. 3357-3366, Vol. 67, No. 7
Department of
Ophthalmology,1 Department of
Microbiology and Immunology,3 and
Molecular Pathogenesis of Eye Infections Research Center,
Dean A. McGee Eye Institute,2 University of
Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
Received 21 December 1998/Returned for modification 3 February
1999/Accepted 12 April 1999
Bacillus cereus is a rare cause of serious human
infection but, paradoxically, causes one of the most severe
posttraumatic or endogenous infections of the eye, endophthalmitis,
which frequently results in blindness. The virulence of B. cereus endophthalmitis historically has been attributed to toxin
production. We therefore sought to examine the contribution of the
dermonecrotic toxin, hemolysin BL, to the pathogenesis of B. cereus infection in an endophthalmitis system that is highly
amenable to study. The pathogenesis of infection resulting from
intravitreal injection of 102 CFU of either a clinical
ocular isolate of B. cereus producing hemolysin BL
(HBL+) or an isogenic mutant in this trait
(HBL
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Role of Hemolysin BL in the Pathogenesis of Extraintestinal
Bacillus cereus Infection Assessed in an
Endophthalmitis Model

) was assessed bacteriologically and by slit lamp
biomicroscopy, electroretinography, histology, and
inflammatory cell enumeration. Both HBL+ and
HBL
strains evoked severe intraocular
inflammatory responses as early as 12 h postinfection, with
complete loss of retinal responsiveness by 12 h. The infections
caused by both strains spread of the infection to adjacent tissues by
18 h. No significant differences in intraocular bacterial growth
(P
0.21) or inflammatory changes
(P
0.21) were observed in eyes infected with either
HBL+ or HBL
strains during the course of
infection. The level of retinal responsiveness was greater in
HBL
infected eyes than in HBL+-infected eyes
at 6 h only (P = 0.01). These results
indicate that hemolysin BL makes no essential contribution to the
severe and rapid course of infection in the endophthalmitis model.
*
Corresponding author. Mailing address: Department of
Ophthalmology, University of Oklahoma Health Sciences Center, 608 Stanton L. Young Blvd., Oklahoma City, OK 73104. Phone: (405) 271-1084. Fax: (405) 271-8128. E-mail: mgilmore{at}aardvark.ou.edu.
Present address: Department of Biology, Oklahoma Baptist
University, Shawnee, Okla.
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