Characterization of viridans group streptococci from endophthalmitis

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Project Summary/Abstract The viridans streptococci are classically considered oral commensals with cariogenic potential; however, these bacteria are also listed among the most common species that cause bacterial endophthalmitis. Exogenous bacterial endophthalmitis can occur following trauma, ocular surgery, or ocular injections. Antibiotics are used to treat this disease, however, antibiotics are only able to kill the bacteria and do not ameliorate the damage to the eye. Streptococcal species in particular are associated with very poor visual outcomes; despite treatment, evisceration or enucleation commonly occur. The immediate objective of this application is to characterize endophthalmitis strains of the viridans streptococci and identify their virulence factors. This objective is intended to initiate study into the broader, long-term objectives of determining the mechanisms of pathogenesis of this important group of species and identify potential targets for future therapies. Two major aims are proposed: 1) to investigate the role of bacterial protease HtrA in endophthalmitis and determine its vitreous and bacterial protein substrates, and 2) to analyze the pangenome and virulence transcriptome of endophthalmitis- causing strains. The first aim will be tested by function analysis of recombinant HtrA variants cloned from the viridans strains and by deletion mutagenesis of htrA from htrA-positive strains, as well as genetic addition of htrA to htrA-negative strains. The second aim will employ whole genome sequencing of 21 strains followed by bioinformatics pangenome analysis to identify conserved genes across the collection, and RNA-seq in vivo and in vitro to determine the virulence transcriptome of this group of species. Accomplishment of these aims will springboard the identification of key factors involved in ocular infection by these species. This research is expected to benefit patient ocular health in the long-term because the knowledge to be gained can aid future therapeutic development.