Time to improve laboratory protocols in microbial keratitis: broad-range Internal Transcribed Spacer sequencing in refractory culture-negative keratitis.
Maria Laura Passaro, Matteo Airaldi, Tobi Somerville et al.
✦ AI-curated · Sources linked
Case in brief
A woman in her 60s who wore soft contact lenses developed rapidly progressive microbial keratitis that did not respond to intensive empirical treatment. Cultures, imaging, cytology and repeated targeted PCR from corneal and aqueous samples were negative. Worsening inflammation, hypopyon, stromal melt and raised intraocular pressure led to anterior chamber washout and therapeutic corneal transplantation with cataract extraction; testing of the excised tissue was also non-diagnostic. After further epithelial breakdown and an anterior chamber mass, sequencing of a removed loose corneal suture detected Fusarium-consistent fungal DNA, prompting targeted antifungal therapy.
What made this case unusual
Broad-range ITS2 rRNA sequencing of a loose corneal suture provided the first microbiological clue after extensive negative testing, although the finding was not corroborated by other tests.
Diagnostic / clinical pearl
In deep, pre-treated keratitis, negative cultures and targeted PCR may not exclude infection; broad-range ITS sequencing of available material such as a loose suture can provide a complementary diagnostic clue.