Pseudallescheria Boydii Keratitis
(Scedosporium Apiospermum)
Raj Yashwanth1*, Anuja1, Suneetha2, Manoharbabu1
Copyright : © 2019 Authors. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
We describe a patient with Pseudallescheria boydii keratitis. The treatment of mycotic keratitis remains difficult This case demonstrates that identification and susceptibility testing should be rapidly performed. In cases of indolent keratitis, the possibility of fungal infection should be kept in mind.
Fungal Keratitis, Pseudallescheria Boydii, scedosporium apiospermum
1. Introduction
2. Case Report
3. Discussion
Scedosporium apiospermum Colonies are fast growing, greyish-white, suede-like to downy with a greyish-black reverse. Numerous single-celled, pale-brown, broadly clavate to ovoid conidia, 4-9 X 6- 10 um, rounded above with truncate bases are observed. Conidia are borne singly or in small groups on elongate, simple or branched conidiophores or laterally on hyphae. Conidial development can be described as annellidic, although the annellations (ring- like scars left at the apex of an annellide after conidial secession) are extremely difficult to see. Optimum temperature for growth is 30-37°C. RG-2 organism.
Ascocarp formation may be stimulated on cornmeal agar or other nutrient deficient media, however it should be noted that many isolates may fail to produce cleistothecia. Cleistothecia (non-ostiolate ascocarps) are yellow-brown to black, spherical, are most- ly submerged in the agar and are composed of irregularly interwoven brown hyphae. When crushed cleistothecia release numerous, faintly brown, ellipsoidal ascospores, 4-5 X 7- 9 µm in size. A Graphium synanamorph may also be present.
The teleomorph is currently referred to as Pseudallescheria boydii, however as all species of Pseudallescheria have Scedosporium anamorphs, it is presumptive to use the teleomorph name to describe this fungus without seeing cleistothecia (ascocarps). Until the taxonomy of Pseudallescheria is resolved, it is recommended that laboratories use the anamorphic name Scedosporium apiospermum when describing this fungus.
In 1979, the Food and Drug Administration approved the clinical use of broad spectrum anti- fungal agents like Natamycin and Miconazole. These drugs were used in the five most recent case reports of Pseudallescheria Boydii keratitis. In two of these five cases, still an enucleation was required [1,3]. This was most probably due to the intensive use of corticosteroids prior to the diagnosis of fungal involvement: diminished host resistance by steroids allows deep invasion of fungi. If a history of trauma by vegetable matter is present, fungal keratitis should always be considered and the use of corticosteroids avoided. The presence of filamentous fungi is easily missed because of the relative absence of fungi in the superficial stromal layers, and the difficulty of culturing them. Therefore repeated, vigorous corneal scraping and/or corneal biopsy is required to confirm a suspected fungal keratitis. The treatment of fun- gal keratitis remains a challenge for each ophthalmologist. At present Natamycin is the recommended first line drug [2]. In deeper fungal infections and those not responding to Natamycin, additional topical therapy, such as Miconazole and Amphotericin B, is required. Pseudallescheria Boydii, however, is often considered to be resistant to Amphotericin B, but the frequency with which this occurs is not well de-scribed [6]. Antifungals are hydrophobic and thus poor penetration of topical antifungals is the rule. Therefore the routine use of systemic antifungals, in particular Itraconazole and Fluconazole, is justified in severe or deep keratitis. Even with optimal medical therapy surgical intervention may be required to eradicate the infection: such measures may include debridement, keratectomy with conjunctival flap and penetrating keratoplasty [2].
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