Abstract
Purpose :
Pseudomonas aeruginosa keratitis is a severe ocular infection that can lead to perforation of the cornea. In this study we evaluated P. aeruginosa-induced corneal perforation and bacterial proliferation in a rabbit keratitis model, and tested whether co-injection of the predatory bacteria Bdellovibrio bacteriovorus could alter the clinical outcome. A lasR quorum sensing mutant bacteria was also included as these have been found recently among keratitis isolates.
Methods :
Rabbit corneas were intrastromally infected with 2000 CFU of P. aeruginosa strain UCBPP-PA14 (PA14) or isogenic △lasR mutant and co-injected with PBS or B. bacteriovorus. After 24 h, eyes were evaluated for clinical signs of infection, a subset was analyzed by scanning electron microscopy, ocular coherence tomography, sectioned for histology, and another subset was homogenized for CFU enumeration and for inflammatory cytokines.
Results :
We observed that 54% of corneas infected by wild-type PA14 presented with a corneal perforation (n=24), whereas only 4% of PA14 infected corneas that were prophylactically treated with B. bacteriovorus perforated (n=25, p<0.01). PA14 proliferation was reduced 7-fold in the predatory bacteria treated eyes (p<0.05). The lasR mutant was less able to proliferate compared to the wild-type (p<0.05), was defective in causing corneal perforation (p<0.01), but was largely unaffected by the predators. IL-1 and MMP9 were significantly higher in eyes injected with PA14 compared to control and predatory bacteria injected eyes, but co-injected eyes and lasR mutant injected eyes and similar levels to PA14.
Conclusions :
These studies indicate a role for bacterial quorum sensing in the ability of P. aeruginosa to proliferate and cause perforation of the rabbit cornea. Additionally, this study suggests that predatory bacteria can reduce the severity of P. aeruginosa pathogenesis in an ocular prophylaxis model and that treatment studies are warranted.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.