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Year : 2012  |  Volume : 55  |  Issue : 2  |  Page : 248-249
Keratomycosis caused by Exserohilum rostratum

1 Department of Microbiology, Mahatma Gandhi Medical College and Research Institute, Pondicherry, India
2 Department of Ophthalmology, Mahatma Gandhi Medical College and Research Institute, Pondicherry, India

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Date of Web Publication3-Jul-2012


We report a case of keratomycosis caused by Exserohilum rostratum. A 46-year-old farmer presented with history of pain, watery discharge and redness of the right eye for the past 2 weeks following trauma with vegetable matter. On ocular examination, a central corneal ulcer of about 8 mm with a greyish-white slough, feathery edges and diffuse corneal edema was seen in the right eye. KOH examination of corneal scrapings revealed thick, brown, branched, septate hyphae. Culture of corneal scrapings on Sabouraud dextrose agar showed velvety greenish-black colony with a black pigment on the reverse. The culture was identified as E. rostratum on the basis of microscopic morphology. The patient responded well to treatment with topical natamycin and oral itraconazole.

Keywords: Corneal ulcer, Exserohilum rostratum, keratomycosis

How to cite this article:
Joseph NM, Kumar M A, Stephen S, Kumar S. Keratomycosis caused by Exserohilum rostratum. Indian J Pathol Microbiol 2012;55:248-9

How to cite this URL:
Joseph NM, Kumar M A, Stephen S, Kumar S. Keratomycosis caused by Exserohilum rostratum. Indian J Pathol Microbiol [serial online] 2012 [cited 2022 Jul 4];55:248-9. Available from: https://www.ijpmonline.org/text.asp?2012/55/2/248/97896

   Introduction Top

Keratomycosis is an invasive fungal infection of the cornea. [1] It usually occurs following corneal trauma by vegetative material contaminated with saprophytic fungi. Majority of the cases of keratomycosis are caused by hyaline fungi such as Aspergillus, Fusarium, Acremonium, Penicillium and Pseudallescheria. The phaeoid fungi such as Alternaria, Curvularia, Exserohilum and Bipolaris are the relatively uncommon causes of keratomycosis. [1] The Exserohilum spp. are usually associated with paranasal sinus, skin and subcutaneous infections, and are only occasionally reported to cause keratomycosis. [2] We report a case of keratomycosis caused by Exserohilum rostratum in an adult patient.

   Case Report Top

A 46-year-old farmer presented with history of pain, watery discharge and redness of the right eye for the past 2 weeks. He gave history of accidental injury to the right eye with vegetable matter while working in the field. After 4 days of injury he had applied some topical eye drops (the exact composition was unknown) for about 6 days, but there was no improvement. As the pain in the eye and watery discharge was persistent, he had come to our ophthalmology clinic for treatment. He is not a diabetic or hypertensive.

On ocular examination, a central corneal ulcer of about 8 mm with a greyish-white slough, feathery edges and diffuse corneal edema was seen in the right eye [Figure 1]a. Both the bulbar and palpebral conjunctiva were diffusely congested. The left eye was normal.
Figure 1: (a) Corneal ulcer with necrotic slough and feathery margins, (b) Sabouraud dextrose agar slant with velvety, greenish-black fungal colony and (c) slide culture preparation showing large, brownpigmented, ellipsoidal, multiseptate conidia with protruding hilum on geniculate conidiophore

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Corneal scrapings were collected under aseptic conditions for microbiological examination. Potassium hydroxide (KOH) examination revealed thick, brown, branched, septate hyphae and Gram stain revealed hyphae with few pus cells and no bacteria. Based on this finding, keratomycosis was suspected and topical natamycin (5%) was administered. Culture on Sabouraud dextrose agar (SDA) showed velvety, grey to green fungal colony after 4 days of incubation at room temperature, which turned to a velvety greenish-black color with a black pigment on the reverse after 8 days of incubation [Figure 1]b. Lactophenol cotton blue preparation of the growth on SDA showed dark brown, septate hyphae and multiseptate conidia. Slide culture was performed to appreciate the intact morphology of the fungus, which revealed large, brown-pigmented, thick-walled, ellipsoidal, multiseptate conidia (seven to eight septae) produced sympodially with predominant protruding hilum on geniculate conidiophores [Figure 1]c. On the basis of these characteristics, the isolate was identified as E. rostratum.

Topical natamycin (5%) was applied hourly for about 1 week along with oral itraconazole 100 mg twice a day. The patient showed clinical signs of improvement, such as diminution of pain, decrease in size of infiltrate, rounding out of the feathery margins of the ulcer and gradual disappearance of the superficial slough. The frequency of application of natamycin was gradually reduced over the next 2 weeks. He responded well to treatment and showed complete resolution.

   Discussion Top

Exserohilum species are common environmental moulds, often encountered in the soil, grass or rotting wood, and they thrive in warm and humid climates. They are rarely pathogenic for human beings, and have been reported as a cause of subcutaneous phaeohyphomycosis, sinusitis, endocarditis, invasive disease and corneal infection. [3],[4]

Species of Fusarium, Aspergillus, Curvularia and Candida are the frequent causes of fungal infections of the cornea. Exserohilum spp. are a relatively rare cause of keratomycosis. [1] Infections caused by Exserohilum are prevalent in regions with hot climates, such as Israel, India and Southern USA. [4] This fungal infection usually occurs in individuals with certain predisposing factors. Invasive and skin infections by Exserohilum occur in those with impaired immunity, whereas local trauma is a predisposing factor for corneal infections. [4],[5],[6] Our patient also reported history of trauma with vegetable matter, following which he developed keratomycosis. Injudicious use of antibiotic and steroid has been identified as a cause of increased incidence of fungal corneal ulcer. In this case, the patient had received initial treatment with an unidentified preparation without any clinical improvement. It is probable that he had used a topical preparation of antibiotics and steroid, which could be the reason for the initial poor response. Corneal ulcers caused by E. rostratum have also been reported in patients without history of trauma and in those with Hansen's disease. [2],[7]

Fusarium solani, a hyaline fungus, usually causes severe infection and perforation and may result in malignant glaucoma and, therefore, completely destroys an eye in a few weeks. However, keratitis due to dematiaceous fungi such as Curvularia species usually presents as superficial feathery infiltration with only slow progression. [1] Our patient infected with E. rostratum, a dematiaceous fungus, also had a superficial feathery keratitis that showed slow progression and responded well to topical application of natamycin and systemic itraconazole. Similarly, in another report of keratomycosis due to E. rostratum, a good response was observed on treatment with topical itraconazole. [2] This suggests that if keratomycosis caused by E. rostratum is treated early with appropriate antifungals, it can result in clinical resolution in most patients.

To conclude, this report of keratomycosis due to E. rostratum emphasizes the necessity to be aware of the possibility of such infection and to properly investigate and treat with appropriate drugs.

   References Top

1.Thomas PA. Fungal infections of the cornea. Eye (Lond) 2003;17:852-62.  Back to cited text no. 1
2.Peerapur BV, Rao SD, Patil S, Mantur BG. Keratomycosis due to Exserohilum rostratum - A case report. Indian J Med Microbiol 2004;22:126-7.  Back to cited text no. 2
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3.Saint-Jean M, St-Germain G, Laferriere C, Tapiero B. Hospital-acquired phaeohyphomycosis due to Exserohilum rostratum in a child with leukemia. Can J Infect Dis Med Microbiol 2007;18:200-2.  Back to cited text no. 3
4.Adler A, Yaniv I, Samra Z, Yacobovich J, Fisher S, Avrahami G, et al. Exserohilum: An emerging human pathogen. Eur J Clin Microbiol Infect Dis 2006;25:247-53.  Back to cited text no. 4
5.Anandi V, George JA, Thomas R, Brahmadathan KN, John TJ. Phaeohyphomycosis of the eye caused by Exserohilum rostratum in India. Mycoses 1991;34:489-91.  Back to cited text no. 5
6.Bouchon CL, Greer DL, Genre CF. Corneal ulcer due to Exserohilum longirostratum. Am J Clin Pathol 1994;101:452-5.  Back to cited text no. 6
7.Mathews MS, Maharajan SV. Exserohilum rostratum causing keratitis in India. Med Mycol 1999;37:131-2.  Back to cited text no. 7

Correspondence Address:
Noyal M Joseph
Department of Microbiology, Mahatma Gandhi Medical College and Research Institute, Pillaiyarkuppam, Pondicherry - 607 402
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0377-4929.97896

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