CASE REPORT Outbreak of Pythium Keratitis During Rainy Season: A Case Series Onsiri Thanathanee, MD,* Orapin Enkvetchakul, MD,* Ram Rangsin, MD, MPH, DrPH,† Sakda Waraasawapati, MD,‡ Kittipan Samerpitak, MSc,§ and Olan Suwan-apichon, MD* Purpose: To describe typical clinical and laboratory characteristics of severe fungal keratitis caused by Pythium insidiosum during the rainy season in Northeast Thailand and to report the efficacy of P. insidiosum vaccine in the treatment of Pythium keratitis. Methods: A series of hospital-based consecutive cases of Pythium keratitis were diagnosed and treated at Srinagarind Hospital (Khon Kaen University, Khon Kaen, Thailand). The clinical presentations, diagnostic tests, and management are described. Results: Severe fungal keratitis caused by P. insidiosum was diag- nosed in 5 eyes of 4 patients between May 2009 and July 2009. All cases had a history of fungal keratitis after being exposed to con- taminated water. Upon slit-lamp examination, subepithelial and superficial stromal opacities were observed in a reticular pattern in all cases. Pythium insidiosum was identified and confirmed by both microbiological culture and polymerase chain reaction. Clinical worsening was detected after conventional treatment with antifungal agents. Therapeutic penetrating keratoplasty with either donor cor- nea or scleral graft was performed together with topical antifungal administration and P. insidiosum vaccination. Subsequent eviscera- tion was performed in 1 eye. Conclusions: An outbreak of Pythium keratitis in Northeast Thai- land was reported. Distinctive clinical features are a suggestive clue for early diagnosis. Combination treatment including topical antifun- gal agents, radical surgery, and P. insidiosum vaccine may be con- sidered for the management of Pythium keratitis. Key Words: Pythium insidiosum, keratitis, vaccine (Cornea 2013;32:199–204) P ythium insidiosum is a pathogen that causes disease in both animals and humans. 1 It is classified in the Phylum Straminipila, Class Oomycetes, Order Pythiales, and Family Pythiaceae. 2,3 Although Pythium keratitis is uncommon, it can be a potentially devastating ocular condition. The P. insidi- osum vaccine—the treatment of choice 4,5 —has reportedly been used in systemic pythiosis, cutaneous pythiosis, and vascular pythiosis, but with a limited outcome. 6,7 Here, we report a combination treatment for Pythium keratitis including topical antifungal administration, therapeutic keratoplasty, and vaccination. Efficacy in prevention of recurrence after vaccination was observed. This study was approved by the Ethics Committee (HE521252) at the Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand. CASE REPORTS Patient 1 A 26-year-old man presented with severe progressive corneal ulcers in both eyes after being exposed to contaminated wastewater. The best-corrected visual acuity was 2/60 and 6/60 in the right and left eyes, respectively. Slit-lamp examination showed a central corneal ulcer with subepithelial and superficial stromal infiltration in a reticular pattern in both eyes, suggestive of a fungal infection (Fig 1, A1 and A2). Gram staining, KOH preparation, and cultures from corneal scraping were negative. He had no underlying systemic or ocular disease. Because his corneal lesions were compatible with fungal keratitis, he was prescribed hourly topical natamycin 5% and ketoconazole 2% with oral ketoconazole at a dosage of 400 mg daily. After 2 days, the patient had progressive worsening of clinical fea- tures. To investigate the causative organisms, confocal microscopy was performed and septate linear branching structures, resembling fungal filaments were observed, corroborating data from the refer- ring hospital. Patient 2 A 50-year-old man presented with pain in his right eye after being exposed to contaminated water in a rice field. On examination, the best- corrected visual acuity at presentation was hand movement in the affected right eye and 6/6 in the left eye (Fig. 1B). The right eye showed dense central stromal opacity surrounded by a reticular pattern of sub- epithelial and superficial stromal infiltration. Hypopyon height of 2.4 mm was noted. Corneal scraping with Gram staining and KOH preparation including confocal microscopy were negative for organisms. As the clinical features were compatible with fungal infection, the patient was treated hourly with 5% natamycin eye drops and 2% ketoconazole eye drops with oral itraconazole at a dosage of 200 mg daily. After a 2-day follow-up period, corneal infiltration progressively Received for publication January 6, 2012; revision received February 25, 2012; accepted February 28, 2012. From the *Department of Ophthalmology, Faculty of Medicine, Srinagarind Hospital, Khon Kaen University, Khon Kaen, Thailand; †Department of Military and Community Medicine, Phramongkutklao College of Medicine, Bangkok, Thailand; Departments of ‡Pathology and §Microbiology, Fac- ulty of Medicine, Srinagarind Hospital, Khon Kaen University, Khon Kaen, Thailand. The authors have no financial or conflicts of interest to disclose. Presented at XXIV Annual Meeting of the Royal College of Ophthalmologists of Thailand, Bangkok, Thailand 2009. Reprints: Olan Suwan-apichon, Department of Ophthalmology, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand (e-mail: osuwanapichon@hotmail.com). Copyright © 2012 by Lippincott Williams & Wilkins Cornea  Volume 32, Number 2, February 2013 www.corneajrnl.com | 199