Filamentous fungal infections of the cornea: a global overview of epidemiology and drug sensitivity

Abstract

Fungal keratitis is a serious suppurative, usually ulcerative corneal infection which may result in blindness or reduced vision. Epidemiological studies indicate that the occurrence of fungal keratitis is higher in warm, humid regions with agricultural economy. The most frequent filamentous fungal genera among the causal agents are Fusarium, Aspergillus and Curvularia. A more successful therapy of fungal keratitis relies on precise identification of the pathogen to the species level using molecular tools. As the sequence analysis of the internal transcribed spacer (ITS) region of the ribosomal RNA gene cluster (rDNA) is not discriminative enough to reveal a species-level diagnosis for several filamentous fungal species highly relevant in keratitis infections, analysis of other loci is also required for an exact diagnosis. Molecular identifications may also reveal the involvement of fungal species which were not previously reported from corneal infections. The routinely applied chemotherapy of fungal keratitis is based on the topical and systemic administration of polyenes and azole compounds. Antifungal susceptibility testing of the causal agents is of special importance due to the emergence and spread of resistance. Testing the applicability of further available antifungals and screening for new, potential compounds for the therapy of fungal keratitis are of highlighted interest.

Freshwater Fungal Infections

“…25,27 Fungal keratitis is much more common in developing countries. 25,26 There is significant geographic variation, even within the same country, regarding the proportion of keratitis that is fungal and the proportional distribution of the various fungal genera as etiologic agents. 26,27 Filamentous fungi, especially Fusarium and Aspergillus, are the primary causes of fungal keratitis in most parts of the world.…”

“…25 The former is especially predominant in tropical and subtropical regions. 26 Other agents include dematiaceous (dark-pigmented) fungi, Scedosporium apiospermum (discussed in more detail on page 36) and other molds. 28 In the United States, Candida species were the predominant causes of fungal keratitis in a New York series and were much more common than Fusarium or Aspergillus.…”

“…5,10 Specific individual preventive measures include use of earplugs while swimming (and, in those with recurrent infection, gently rinsing the ear canals after swimming with equal portions of vinegar and rubbing alcohol) to prevent AOE, 37 and washing feet thoroughly after public swimming or bathing. 53 Additionally, one should ensure proper use of contact lenses (including therapeutic lenses) and contact lens solution (avoiding tap water), 26 wash all wounds thoroughly and take care not to aspirate potentially contaminated freshwater. Special care for the immunocompromised may include enhanced monitoring of hospital water supplies, avoidance of hospital (and sometimes domestic) tap water and showers and rigorous handwashing by all patients and personnel.…”

“…Identification of the causative organism is generally through culture with or without biopsy, 25 but perhaps more appropriately with molecular techniques. 26 Ophthalmological treatment generally includes a topical antifungal (typically 5% natamycin) with or without topical amphotericin B or systemic antifungals. 25,26 Debridement or more extensive surgery may be required.…”

“…26 Ophthalmological treatment generally includes a topical antifungal (typically 5% natamycin) with or without topical amphotericin B or systemic antifungals. 25,26 Debridement or more extensive surgery may be required. 25 Therefore, all cases should be managed by an ophthalmologist trained in the diagnosis and treatment of these difficult infections.…”