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B. J. Wiskur, J. J. Hunt, M. C. Callegan; Hypermucoviscosity as a Virulence Factor in Experimental Klebsiella pneumoniae Endophthalmitis. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3163.
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To compare the intraocular virulence of hypermucoviscous (HMV+) and non-hypermucoviscous (HMV-) strains of Klebsiella pneumoniae during experimental endophthalmitis.
C57BL6J mice were injected in the midvitreous with 100 colony forming units (CFU) of HMV+ or HMV- Klebsiella pneumoniae. During the course infection, a- and b-wave function were monitored by electroretinography (ERG) every 3 hours until all retinal function was lost or the infection was effectively cleared. Viable bacteria per eye were quantified by track plating 10-fold serial dilutions onto brain heart infusion agar. Gross pathology of the infection was analyzed by histology.
HMV+ and HMV- strains grew logarithmically in the eye until approximately 15 hours postinfection. A stationary phase of growth was reached shortly thereafter at approximately 8 log10 CFU/eye for all eyes infected with the HMV+ strain and 1/3 of eyes infected with the HMV- strain. The remaining 2/3 of eyes infected with HMV- K. pneumoniae cleared the infection by 27 hours. Eyes infected with HMV+ K. pneumoniae experienced severe inflammation and rapid retinal function loss over an 18-hour time period. Intraocular inflammation, including influx of inflammatory cells into the anterior chamber and cornea, reached severe levels by 15 to18 hours postinfection in eyes infected with the HMV+ strain. Eyes infected with HMV- K. pneumoniae experienced moderate inflammation and a moderate decline in retinal function until 21 hours postinfection in 2/3 of the animals, with improvement of function correlating with infection clearance by 27 hours postinfection.
Our findings demonstrate the importance of the hypermucoviscosity phenotype in the pathogenesis of experimental K. pneumoniae endophthalmitis. Future studies are focused on the role of this virulence factor in the development of endogenous K. pneumoniae endophthalmitis and the dynamic interactions between the pathogen and immune system in the evolution of disease.
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