Case Series: Mixed Infectious Keratitis by Pythium insidiosum and Fungal Species

Abstract

Significance: This case series is the first to illustrate mixed infection from Pythium sp. and fungal species in corneal ulcer.

Purpose: This case series aimed to alert all toward the possibility of both Pythium sp. and fungal species infection in case of nonresponding corneal ulcer treated with either antifungals or antipythium drugs alone. Increased suspicion of mixed infection in case of nonresponding fungal/ Pythium keratitis may facilitate early and prompt management.

Case reports: Six patients presented with signs of either fungal or Pythium keratitis. They underwent ophthalmological examinations, smear examinations, cultures, and polymerase chain reaction (PCR). Therapeutic penetrating keratoplasty was performed in cases where symptoms worsened after treatment with either antifungal or antipythium drugs. The half corneal button (HCB) was shared for histopathological and microbiological examinations. In the first case, smear examination from corneal scraping (CS) revealed Pythium -like filaments, which were confirmed with PCR; however, Aspergillus nidulans grew in culture. In the second case, iodine-potassium iodide (IKI) staining was positive for Pythium ; however, PCR was positive for both Pythium and fungus, which was further confirmed by DNA sequencing. In the third case, IKI staining and HCB were positive for Pythium ; however, PCR was positive for fungus, which was identified as Candida saitoana with DNA sequencing. In the fourth case, Pythium grew in the CS culture; however, Candida sp. grew in the HCB culture. In the fifth case, Cladosporium sp. grew in culture from CS; however, Pythium insidiosum grew from the anterior chamber exudate after therapeutic penetrating keratoplasty. In the sixth case, smear examination revealed septate fungal filaments, and Cladosporium sp. grew in culture; however, HCB on histopathological examination showed features of Pythium keratitis.

Conclusions: In unresponsive cases of Pythium or fungal keratitis, diagnostic modalities such as IKI and PCR should be implemented as a routine practice, in addition to smears and cultures.