Abstract
Purpose::
To ascertain the role of bacterial immune inhibitors InhA and InhA2 in experimental Bacillus endophthalmitis.
Methods::
Bacillus thuringiensis strain 407 (WT) and isogenic mutants of immune inhibitors A and A2 (InhA, InhA2) were tested in the rabbit model of post-traumatic experimental endophthalmitis. Eyes were injected intravitreally with 100 CFU of strain BT407, InhA-, InhA2-, or InhA-/InhA2-. Pathogenesis was monitored by electroretinography, bacterial enumeration, and histology.
Results::
The intraocular growth rates of Bacillus mutants InhA2- and InhA-/InhA2- were significantly higher than that of WT and InhA- at early time points, but all strains reached similar intraocular numbers by 12 hours postinfection. Interestingly, all Inh mutants caused near complete loss of retinal function by 12 hours postinfection, while animals infected with the wild type strain retained 40% B-wave function by electroretinogram. Additionally, Inh mutants exhibited increased kinetics of ERG B-wave loss during the course of infection. Intraocular inflammation reached severe levels by 12 hours postinfection in eyes infected with each strain.
Conclusions::
Both wild type Bacillus and its Inh mutants had a devastating effect, causing severe visual function loss and significant inflammation by 12 hours postinfection. However, the presence of InhA and InhA2 may have been responsible for a slight attenuation of infection. Overall, the results suggested that InhA and InhA2 may not play a prominent role in the pathogenesis of experimental Bacillus endophthalmitis.
Keywords: bacterial disease • endophthalmitis • microbial pathogenesis: experimental studies