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Published on: March 17, 2014
Pathogenic phenotype and genotype of Pseudomonas aeruginosa isolates from spontaneous canine ocular infections
Eric C Ledbetter1, James J Mun, David Kowbel
1College of Veterinary Medicine, Department of Clinical Sciences, Cornell University, Ithaca, New York 14853-6414, USA. ecl32@cornell.edu
Purpose:
This study was designed to determine whether the ability to adversely affect corneal epithelial cell health is a factor common to Pseudomonas aeruginosa keratitis strains and to assess the prevalence of each pathogenic phenotype and genotype in a canine model of naturally-acquired P. aeruginosa ocular infection.
Methods:
P. aeruginosa ocular isolates were collected by sampling 100 dogs without disease (six isolates collected) and by sampling dogs with conjunctivitis (two isolates), endophthalmitis (one isolate), active keratitis (12 isolates), and resolved P. aeruginosa keratitis (four isolates). Phenotype was determined in vitro by quantifying corneal epithelial cell invasion by gentamicin survival assays, and cytotoxic activity by Trypan blue exclusion assays. Genotyping was performed for genes encoding the type III secreted effectors.
Results:
The ratio of invasive to cytotoxic strains with 95% confidence intervals (CI) was 0.83 (CI, 0.42-0.99) for conjunctival microflora isolates, 0.80 (CI, 0.54-0.94) for ocular infection isolates, and 1.0 (CI, 0.45-1.0) for strains isolated post-resolution of keratitis. Among ocular infection isolates, invasive and cytotoxic strains were significantly (P
Conclusions:
Invasive strains predominated in the dogs of this study. Only keratitis strains had visible adverse effects on epithelial cells without overt cytotoxicity, suggesting virulence strategies affecting live corneal epithelial cell health are selected for among keratitis strains.
Insights
Pseudomonas aeruginosa keratitis strains can harm corneal cells. Invasive strains were common in dogs, with some keratitis strains showing unique virulence strategies.
Area of Science:
- Ophthalmology
- Microbiology
- Veterinary Medicine
Background:
- Pseudomonas aeruginosa (P. aeruginosa) is a significant cause of bacterial keratitis.
- Understanding the virulence factors of P. aeruginosa is crucial for treating ocular infections.
Purpose of the Study:
- To determine if P. aeruginosa keratitis strains commonly affect corneal epithelial cell health.
- To assess the prevalence of pathogenic phenotypes and genotypes in canine P. aeruginosa ocular infections.
Main Methods:
- Collected P. aeruginosa isolates from dogs with and without ocular disease.
- Assessed corneal epithelial cell invasion and cytotoxicity in vitro.
- Performed genotyping for type III secreted effector genes.
Main Results:
- Invasive P. aeruginosa strains predominated in the canine population studied.
- Keratitis strains showed significantly more adverse effects on epithelial cells compared to other isolates.
- Only a subset of keratitis strains possessed the ExoU gene, indicating varied virulence mechanisms.
Conclusions:
- Invasive P. aeruginosa strains are prevalent in canine ocular infections.
- Keratitis-associated P. aeruginosa strains exhibit distinct virulence strategies targeting corneal epithelial cells.
- Virulence mechanisms affecting corneal epithelial cell health are selected for in P. aeruginosa keratitis.
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