Vitreous metagenomic detection of Rickettsia felis in culture-negative endogenous endophthalmitis: a case report

Abstract Background To present a rare case of severe culture-negative endogenous endophthalmitis in which vitreous metagenomic next-generation sequencing (mNGS) detected Rickettsia felis , highlighting its atypical ocular presentation, diagnostic challenges, and interpretive limitations. Case presentation A 72-year-old woman presented with progressive visual loss, redness, and ocular pain in the right eye for 2 weeks. She had no recent ocular surgery, ocular trauma, or corneal ulceration, and had been treated elsewhere for presumed uveitis without improvement. Visual acuity was light perception in the right eye. Slit-lamp examination showed mixed conjunctival injection, fine gray-white keratic precipitates, marked anterior chamber inflammation, extensive posterior synechiae, and cataract. The fundus was obscured by dense vitreous opacity. White blood cell count was 9.89 × 10^9/L and C-reactive protein level was 60.33 mg/L. Urgent pars plana vitrectomy with cataract extraction, empirical intravitreal vancomycin and ceftazidime, laser photocoagulation, and silicone oil tamponade was performed. Intraoperatively, dense white vitreous exudates, retinal arterial whitening, multifocal white retinal lesions, peripheral retinal necrosis, and circumferential exudative plaques involving the peripheral retina and pars plana were observed. Vitreous bacterial and fungal smears and cultures were negative. Vitreous metagenomic next-generation sequencing detected Rickettsia felis with 7,912 reads, 71.3% relative abundance, and 29.5% genome coverage. Targeted exposure history was negative, and echocardiography showed no definite valvular vegetations. Visual acuity improved to hand motions by postoperative day 8. At 8 weeks, the retina remained attached, although optical coherence tomography showed retinal thinning, atrophy, and disorganization. Conclusions This case suggests that Rickettsia felis may be considered in the differential diagnosis of severe culture-negative endogenous endophthalmitis with necrotizing retinal and vascular features. Vitreous metagenomic next-generation sequencing may help identify unexpected intracellular pathogens, but aetiological attribution should be made cautiously in the absence of paired serology, targeted polymerase chain reaction confirmation, or definite epidemiologic exposure.