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Updated: Jul 4, 2026
Intravitreal Injection and Quantitation of Infection Parameters in a Mouse Model of Bacterial Endophthalmitis
Published on: February 6, 2021
Hypermucoviscosity as a virulence factor in experimental Klebsiella pneumoniae endophthalmitis
Brandt J Wiskur1, Jonathan J Hunt, Michelle C Callegan
1Oklahoma Center for Neuroscience, University of Oklahoma HealthSciences Center, Oklahoma City, Oklahoma, USA.
Purpose:
Klebsiella pneumoniae is a common cause of endogenous bacterial endophthalmitis, a disease that frequently results in a poor visual outcome. Hypermucoviscosity has been identified as a virulence factor among clinical bacteremia isolates of K. pneumoniae. In this study, an experimental murine model of K. pneumoniae endophthalmitis was established, and the role of hypermucoviscosity in its pathogenesis was analyzed.
Methods:
C57BL/6J mice were intravitreously injected with 100 CFU of hypermucoviscous (HMV+) or nonhypermucoviscous (HMV-) K. pneumoniae. Intraocular bacterial growth, retinal function, gross pathology, and inflammatory responses were monitored every 3 hours until the eyes lost significant (>90%) retinal function, or the infection appeared to clear.
Results:
The HMV+ strain grew logarithmically in eyes until approximately 15 hours postinfection (PI), reaching a stationary phase of growth at approximately 8.0 log(10) CFU/eye. The HMV- strain grew logarithmically to approximately 7.6 log(10) by 18 hours, but bacterial count declined to approximately 6.4 log(10) CFU/eye by 21 hours PI. Eyes infected with the HMV+ strain retained approximately 35% a-wave and <10% b-wave function by 18 hours PI. These eyes also had a cumulative clinical score of 14+ by 18 hours and underwent phthisis between 21 and 24 hours. Eyes infected with the HMV- strain had a cumulative clinical score of <6 and retained >60% a-wave and >50% b-wave function throughout 21 hours. Five of 7 eyes had <100 CFU HMV- K. pneumoniae at 27 hours PI.
Conclusions:
The findings demonstrate the site-threatening consequences of K. pneumoniae endophthalmitis and the importance of the hypermucoviscosity phenotype in the pathogenesis of experimental K. pneumoniae endophthalmitis.
Insights
Hypermucoviscous Klebsiella pneumoniae causes severe endophthalmitis in mice, leading to rapid vision loss and eye damage. Non-hypermucoviscous strains were cleared more effectively, suggesting hypermucoviscosity is a key virulence factor.
Area of Science:
- Ophthalmology
- Microbiology
- Infectious Diseases
Background:
- Klebsiella pneumoniae is a frequent cause of bacterial endophthalmitis.
- Endophthalmitis often leads to poor visual outcomes.
- Hypermucoviscosity is a known virulence factor in K. pneumoniae.
Purpose of the Study:
- To analyze the role of hypermucoviscosity in K. pneumoniae endophthalmitis pathogenesis.
- To establish and utilize a murine model for studying K. pneumoniae endophthalmitis.
Main Methods:
- Intravitreal injection of hypermucoviscous (HMV+) or nonhypermucoviscous (HMV-) K. pneumoniae into C57BL/6J mice.
- Monitoring of intraocular bacterial growth, retinal function (a-wave, b-wave), and gross pathology postinfection.
Main Results:
- HMV+ K. pneumoniae exhibited logarithmic growth, reaching stationary phase by 15 hours.
- HMV- K. pneumoniae showed limited growth and subsequent clearance by 21 hours.
- Eyes infected with HMV+ strains showed significant retinal function loss and severe pathology, progressing to phthisis.
Conclusions:
- Hypermucoviscosity significantly contributes to the pathogenesis of K. pneumoniae endophthalmitis.
- The hypermucoviscosity phenotype is critical for severe disease progression and poor visual outcomes.
- This study highlights the site-threatening nature of K. pneumoniae endophthalmitis.
