Risk Factors, Clinical Characteristics, and Antibiotic Susceptibility Patterns of Streptococcal Keratitis: An 18-Year Retrospective Study from a Tertiary Hospital in China

<b>Purpose:</b> Our aim was to investigate risk factors, clinical characteristics, and antibiotic susceptibility patterns of cornea-isolated <i>Streptococcus</i> species collected at a tertiary hospital in China over 18 years. <b>Methods:</b> This retrospective study reviewed data from 350 patients diagnosed with <i>Streptococcal</i> keratitis at Beijing Tongren Hospital between January 2006 and December 2023, including demographics, risk factors, clinical signs, in vivo confocal microscopy (IVCM) imaging, and antibiotic susceptibility testing. <b>Results:</b> The predominant type was <i>Streptococcus pneumoniae</i> (n = 108, 29.8%), followed by <i>Streptococcus mitis</i> (n = 90, 24.9%) and <i>Streptococcus oralis</i> (n = 85, 23.5%). Main risk factors included previous ocular surface disease (24.6%), ocular surgery (21.4%), and trauma (16.3%). Significant differences in clinical characteristics were observed among <i>S. pneumoniae</i>, <i>S. oralis</i>, and <i>S. mitis</i> regarding infiltration location (<i>p</i> = 0.038) and size (<i>p</i> = 0.037), as well as hypopyon presence (<i>p</i> = 0.006). IVCM revealed deeper inflammatory cell distribution and structural disruption as the disease progressed. Resistance rates of aminoglycosides, β-lactams, and fluoroquinolones have increased, with significant differences among species for amikacin (<i>p</i> = 0.010), gentamicin (<i>p</i> = 0.007), and others. Poor outcomes correlated with disease duration over one month, central corneal ulcers, dense infiltrations, hypopyon, and scar tissue presence on IVCM. <b>Conclusions:</b><i>Streptococcal</i> keratitis is a complex ocular infection with multiple risk factors. <i>S. pneumoniae</i>, <i>S. mitis</i>, and <i>S. oralis</i> are the primary causative agents, exhibiting varying clinical features and antibiotic resistance patterns. Key factors associated with poor outcomes include long disease duration, central corneal ulcers, and severe infiltration.