Serratia marcescens keratitis: strain-specific corneal pathogenesis in rabbits
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Published on: January 8, 2020
E B Hume1, L L Conerly, J M Moreau
1Louisiana State University Medical Center, Department of Microbiology, Immunology, and Parasitology, New Orleans, LA 70112-1393, USA.
Purpose:
The purpose of this study was to develop an animal model of Serratia keratitis that is suitable to demonstrate the pathology of specific strains.
Methods:
Serratia marcescens ocular strains 93-1399-1 and 94-EI-185-2, and an environmental strain (ATCC 14041) were characterized in vitro in terms of their motility, metabolic profiles, ribotypes, and protease production. The strains were then analyzed in the rabbit intrastromal injection model. Slit lamp examination (SLE) and enumeration of bacteria in the cornea was conducted every 6 hours for 30 hours post-infection. In vivo motilities were analyzed by quantification of bacteria in the peripheral and central areas of infected rabbit corneas.
Results:
All strains were similar in their metabolic activity and production of extracellular proteases. The ocular isolates were distinct from the environmental strain in their ribotyping patterns and in their motility. Each strain grew logarithmically in the cornea up to 6 hours post-infection. SLE scores increased from 0 to 30 hours post-infection for strains ATCC 14041 and 93-1399-1, while the SLE score of strain 94-EI-185-2 reached its maximum at 18 hours post-infection. Strain-specific differences in pathology were noted from 18 to 30 hours post-infection. Strain 94-EI-185-2 produced iritis but only mild corneal changes. Strain 93-1399-1 produced a severe corneal infiltrate encompassing the entire corneal surface as well as severe conjunctival inflammation and iritis. Strain ATCC 14041 produced a localized, severe, exudative corneal abscess that contained infecting bacteria.
Conclusions:
A rabbit model of Serratia keratitis was developed in which bacterial growth kinetics and strain-specific ocular pathologic changes were reproducible.
Insights
A new rabbit model for Serratia keratitis was developed. This model effectively shows reproducible bacterial growth and distinct, strain-specific ocular pathology in Serratia marcescens infections.
Area of Science:
- Ophthalmology
- Microbiology
- Infectious Diseases
Background:
- Serratia marcescens is a significant cause of microbial keratitis.
- Developing reliable animal models is crucial for understanding disease pathogenesis and evaluating treatments.
Purpose of the Study:
- To establish a reproducible rabbit model of Serratia keratitis.
- To demonstrate strain-specific pathological differences in Serratia marcescens infections.
Main Methods:
- Characterization of Serratia marcescens strains (ocular and environmental) in vitro (motility, metabolic profiles, ribotypes, protease production).
- Intrastromal injection into rabbit corneas.
- Serial slit-lamp examination (SLE) and bacterial enumeration for 30 hours post-infection.
Main Results:
- All strains exhibited logarithmic growth in the cornea up to 6 hours.
- Strain-specific differences in corneal pathology and inflammation were observed between 18 and 30 hours post-infection.
- Strain 93-1399-1 caused severe keratitis and iritis; strain 94-EI-185-2 caused iritis with mild corneal changes; strain ATCC 14041 formed a localized corneal abscess.
Conclusions:
- A reproducible rabbit model for studying Serratia keratitis was successfully developed.
- The model allows for the observation of bacterial kinetics and distinct, strain-dependent ocular disease manifestations.
