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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 58  |  Issue : 4  |  Page : 239-244

Dematiaceous fungal keratitis: Clinical and microbiologic experience


Department of Cornea and Refractive Surgery, Aravind Eye Hospital, Tirunelveli, Tamil Nadu, India

Date of Submission14-Jun-2020
Date of Decision04-Aug-2020
Date of Acceptance21-Sep-2020
Date of Web Publication16-Dec-2020

Correspondence Address:
Dr. Pratik Gajanan Kunde
Department of Cornea and Refractive Surgery, Aravind Eye Hospital, Tirunelveli, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/tjosr.tjosr_71_20

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  Abstract 


Objective: The objective was to study the epidemiology, clinical features, and treatment outcomes of dematiaceous fungal keratitis. Design: This was a retrospective, noncomparative, observational study. Materials and Methods: Fifty-nine cases of dematiaceous fungal keratitis seen at tertiary care hospital from January 2017 to June 2018 were analyzed for demographic features, predisposing factors, clinical characteristics, microbiological profile, and treatment outcomes. Statistical Analysis: Mean (standard deviation) and frequency (percentage) were used to represent continuous and categorical variables, respectively. Wilcoxon signed rank test was used for comparative analysis. Results: Of 236 cases of fungal keratitis seen during the study period, dematiaceous fungi were the third most common isolates in 59 cases (25%) after Fusarium (n = 101; 43%) and Aspergillus species (n = 76; 32%). Majority of the patients were adult males (male: female = 2:1) from rural areas (51%) with agricultural occupation (51%). Trauma with vegetable matter was the most common predisposing factor in 27 cases (45.8%). The characteristic macroscopic pigmentation was seen in only eight eyes (13.6%). In our study, 24 (40.7%) patients revealed Curvularia species, followed by Bipolaris and Exserohilum species in 20 cases (33.9%) and 10 cases (17%), respectively. The median time of antifungal therapy was 21 days (interquartile range: 21–41 days). Fifty-four (91.5%) responded to medical therapy, whereas five eyes required surgical intervention. Conclusions: This study signifies the importance of dematiaceous fungi as the important causative agent of fungal keratitis. Medical therapy along with debridement of ulcer alone can be effective in treating patients with superficial infiltrate who seek treatment early.

Keywords: Dematiaceous, fungal keratitis, keratomycosis, pigmented fungi


How to cite this article:
Kunde PG, Anitha V, Meenakshi R, Fathima S H. Dematiaceous fungal keratitis: Clinical and microbiologic experience. TNOA J Ophthalmic Sci Res 2020;58:239-44

How to cite this URL:
Kunde PG, Anitha V, Meenakshi R, Fathima S H. Dematiaceous fungal keratitis: Clinical and microbiologic experience. TNOA J Ophthalmic Sci Res [serial online] 2020 [cited 2021 Jan 21];58:239-44. Available from: https://www.tnoajosr.com/text.asp?2020/58/4/239/303654




  Introduction Top


Fungal keratitis is one of the leading causes of visual morbidity and blindness. According to one report from South India, 44% of all central corneal ulcers are caused by fungi.[1] Dematiaceous fungal keratitis accounts for 15.7% of all fungal keratitis in India. Curvularia species predominates the pigmented fungal spectrum followed by Bipolaris and Exserohilum.[2] Treatment of fungal keratitis is generally more difficult than that of bacterial ulcers, resulting visual impairment is more severe.[3] In this study and present the clinical and microbiologic features with treatment outcomes in cases of dematiaceous fungal keratitis diagnosed at tertiary care hospital.


  Materials and Methods Top


Medical and microbiologic records of culture-proven cases of dematiaceous fungal keratitis diagnosed from January 2017 to June 2018 were documented for demographic features, predisposing factors, past treatment history, clinical features, microbiologic findings, medical and surgical treatment, complications, and outcome of therapy. Detailed history of patient's residence (urban or rural), occupation, associated systemic disease, prior ocular trauma, treatment received, or use of native medication such as breast milk was recorded. All patients underwent thorough slit-lamp examination. The site, size, depth, and nature of the infiltrate; presence of pigmentation; endothelial exudates; and anterior chamber reaction or hypopyon were recorded at the time of presentation.

As a routine, corneal scrapings were obtained from all patients with corneal ulcers using a sterile Kimura's spatula under topical anesthesia with 1% proparacaine hydrochloride. After removing the debris in the vicinity of the ulcer, material obtained from the base and edges was evaluated microscopically using potassium hydroxide (10.0% KOH) wet mount and Gram staining method. Samples were inoculated into various culture media, namely, blood agar, Chocolate agar, and Potato dextrose agar. The smears were stained and studied under light microscope immediately. The inoculated culture plates were incubated at 37°C, except for Potato dextrose agar, which was incubated at 25°C. Cultures were kept for a minimum of 2 weeks before being declared culture negative.

An isolate was considered as a dematiaceous if:

  1. Fungal colonies revealed brown or black pigmentation.[Figure 1]
  2. Lactophenol cotton blue mount from the culture revealed brown or black pigmented hyphae, conidia or both [Figure 2].
Figure 1: Culture plate showing Curvularia species

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Figure 2: Lactophenol cotton blue mount showing Curvularia species with spores and filaments

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The patency of the lacrimal duct was tested. Other investigations such as random blood sugar and blood pressure recording were done in all cases. Patients with corneal ulcers whose KOH smear and Gram's smear showed the presence of fungi, were treated with antifungals. Medical treatment was based on the smear results and was modified depending on the clinical response and culture results.

Treatment protocol

Treatment consisted of application of topical Natamycin 5% with a dose of one drop every hour for the first 3 days followed by one drop every 2 h and tapered until the resolution of the ulcers. Topical Voriconazole 1% (Vozole; 30 mg sterile lyophilized powder reconstituted in 3 mL of sterile water; Aurolab, India) was added for patients who presented with hypopyon, not responding to Natamycin alone and/or ulcers >5 mm. Cycloplegic eye drops were also administered to all patients two times a day. Systemic antifungals (tablet fluconozole 200 mg OD) were added for the patients with deeper involvement, associated features such as hypopyon, larger size and nonhealing ulcers. The treatment was continued for at least 3 weeks after complete resolution of the infiltrate.

Clinical cure is defined as healing of corneal epithelium and scarring of the cornea assessed by:

  1. Decrease in symptoms
  2. Decrease in size of ulcer
  3. Decrease/complete resolution of hypopyon
  4. Resolution of corneal infiltrate.


If there were no signs of healing for 3 weeks, surgery was planned (amniotic membrane grafting, penetrating keratoplasty [TPK]).

Indication for AMT

To promote re-epithelialization in nonhealing ulcers or to prevent corneal perforation.

Indications for penetrating keratoplasty

  1. Perforation, descemetocele
  2. Persistent nonhealing or progressive ulcer along with symptoms for more than 3 weeks
  3. Early vitreous and scleral involvement.


Statistical analysis

The statistical analysis was performed by STATA11.1 (StataCorp, College Station, Texas, USA), Continuous variables were represented as “mean (standard deviation [SD])” and categorical variables were represented as “frequency (percentage).” Mean values of pre and post treatment of ocular parameters were compared by Wilcoxon signed rank test. P < 0.05 was considered statistically significant.


  Results Top


Demographic data

Most patients were male, the male-to-female ratio being 2:1 [Table 1]. Age of the patients varied from 20 to 73 years (mean – 55.44 years; standard deviation – 12.3 years) [Figure 3]. Thirty-six patients (51%) belonged to rural areas, whereas 23 (39%) patients were from urban areas. Majority of the patients were farmers 30 (50.9%), while 15 (25.4%) were Industrial workers. The remaining 14 (23.7%) patients belonged to nonworking population [Figure 4].
Table 1: Gender distribution

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Figure 3: Age distribution of patients

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Figure 4: Occupation of patients

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Time of presentation of symptoms

Majority of the patients (n = 49; 83.1%) presented within one week of onset of symptoms. Only two (3.4%) patients presented after one month of onset of symptoms [Figure 5].
Figure 5: Time of presentation of symptoms

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Predisposing factors

Thirty-seven eyes (62.7%) had a history of trauma before the onset of symptoms. The most common form of injury was trauma with vegetable matter [Table 2].
Table 2: Ocular and systemic predisposing factors

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Prior history of using medication

Eighteen eyes (30.5%) received some form of topical treatment before they were examined at our institute as shown in [Table 3].
Table 3: History of prior medications

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Clinical features

The most common symptoms at presentation were redness, watering, photophobia, and decreased vision of variable severity. Thirty-two eyes (54.2%) had a yellow-white infiltrate with dry, raised slough and feathery edges, while remaining 27 eyes did not show typical clinical features of fungal ulcer. Ulcers in 20 (33.9%) patients were centrally located involving the pupillary axis [Figure 6], while 39 (66.1%) patients showed peripherally located ulcers [Figure 7].
Figure 6: Centrally located ulcer characteristic macroscopic pigmentation

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Figure 7: Peripherally located pigmented ulcer

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The infiltrate was superficial and confined to the anterior (1/3rd thickness) in 32 eyes (54.2%), mid stroma (1/3-2/3) in 18 eyes (30.5%), whereas in nine eyes (15.3%) even the deep stroma (>2/3) was involved. The size of the infiltrate in its largest diameter varied from 2 to 7 mm, with a mean of 3.05 ± 1.1 mm. The characteristic macroscopic pigmentation was seen in only eight eyes (13.6%). Hypopyon was present in 19 eyes (32.2%) ranging from <0.5 mm to 3 mm in height.

Microbiologic analysis

Results of microscopic examination are shown in [Figure 8]. Among the 236 culture-proven cases of fungal keratitis, Fusarium and Aspergillus species dominated the spectrum and were recovered from 101 eyes (43%) and 76 eyes (32%), respectively. The dematiaceous group of fungi accounted for infection in 59 cases (25%).
Figure 8: Incidence of different fungal species

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Among patients with keratitis due to dematiaceous group of fungi, the most common species was Curvularia (n = 24, [40.7%]) followed by Bipolaris species and Exserohilum species [Table 4] and [Figure 9].
Figure 9: Incidence of dematiaceous species

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Table 4: Incidence of Dematiaceous species

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Mean duration of appearance of growth in culture

Mean (SD) duration of appearance of growth in culture medium was 5.10 ± 2.3 days of inoculation (range: 2–14 days). Majority 42 (71.2%) showed growth between 4 and 7 days. Only six (10.2%) showed growth after 7 days of culture [Figure 10].
Figure 10: Mean duration of appearance of growth in culture

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Treatment

All 59 cases in our study were treated by antifungal agents according to treatment protocol after the diagnosis was confirmed microbiologically. Twenty-nine (49.1%) cases received topical natamycin alone, while 30 (50.8%) cases also received topical 1% Voriconazole hourly, in addition to natamycin.

Twenty-six (44%) cases in our study received both topical and oral antifungal agents. Oral therapy was given as fluconazole 200 mg once daily.

Three (5.1%) patients underwent therapeutic debridement with amniotic membrane transplantation to support the healing process of the ulcer. Monolayer amniotic membrane was sutured to the surface of the bulbar conjunctiva with 8–0 vicryl sutures. Penetrating keratoplasty was performed in two cases of perforation (3.4%). An intracameral injection of voriconazole (100μg/0.1mL) was given at the end of surgery. The quality of donor tissue was fair to good in all cases. Topical and systemic antifungal therapy was continued in the postoperative period.

Treatment outcome

Fifty-four (91.6%) cases achieved clinical cure with medical therapy with resolution of infiltrate and scar formation. Out of these cases, 34 needed repeated therapeutic scraping along with medical therapy [Table 5]. The median time of antifungal therapy was 21 days (interquartile range: 21–41 days). In both cases of therapeutic keratoplasty, opaque graft with no recurrence was noted at the last follow-up. Nil intraoperative and postoperative complications were noted in surgically intervened cases.
Table 5: Treatment outcomes

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Visual outcome

The analysis using Wilcoxon sign rank test [Table 6] showed that there was a significant difference (P = 0.001) in visual acuity at baseline and at 6 months.
Table 6: Visual outcome

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  Discussion Top


In the different studies, incidence of mycotic keratitis has been found to be 6% to 50% of all cases of ulcerative keratitis.[4],[5],[6],[7],[8],[9] The term dematiaceous fungi refers to darkly pigmented filamentary moulds, that constitutively produces melanin.[2],[10] It is a subtype of filamentous fungi which includes species Alternaria, Curvalaria, Bipolaris, Exserohilum.[11]

Two hundred and thirty-six cases of fungal keratitis were diagnosed at our institute from January 2017 to June 2018 which constituted 30.2% of all culture-proven cases of infectious keratitis. Of these fungal isolates, dematiaceous fungi were the third most common etiologic agents (25%) after Fusarium (43%) and Aspergillus species (32%). In a study by Garg et al., of 565 fungal isolates from cases of keratitis, dematiaceous fungi were reported as the third (15.7%) most common in the series after Fusarium species (36.6%) and Aspergillus species (30.4%).[2] Results of our studies are comparable with slightly more incidence of dematiaceous fungal keratitis.

Dematiaceous fungal keratitis is more prevalent among rural population living in hot and humid climates; trauma with vegetable matter being most important predisposing factor.[11],[12],[13] Ocular trauma was the predisposing factor in 62.7% eyes, which is not very different from that reported for fungal keratitis in general.[3] Typical presentation of a yellow-white localized infiltrate with a dry raised slough having feathery edges was present in significant proportion of patients (54.2%) at initial examination. The majority of ulcers was peripherally located (66%) and involved anterior 2/3rd of stroma (85%). The characteristic macroscopic pigmentation was present in only 13.6% of eyes. Although visible pigmented infiltrate can be an important diagnostic clue, it is important to establish an accurate diagnosis through microscopic evaluation and culture.[14],[15],[16] It is possible that the pigmentation was masked to a great extent by the presence of a marked stromal inflammation.[17] Pigmented plaque is characterized by the presence of heavy load of fungal filaments on the surface of cornea. Excision of the plaque helps in reducing the fungal load.[15]

Since no other microorganism is known to produce clinically pigmented corneal ulcers, it can be concluded that in the presence of pigmented infiltrate, one could be confident of the treatment to be adopted for eliminating fungal infection.[2] This information can be of great importance to ophthalmologists treating cases of infectious keratitis on an empirical basis. Such cases can be best treated with therapeutic debridement of the infiltrate followed by institution of antifungal therapy.

In our sudy, Curvularia species was the most frequent pigmented fungal pathogen (33.9%), followed by Bipolaris and Exserohilum species. Many other investigators have reported Curvularia as the most frequent pigmented fungal pathogen in corneal ulcers.[2],[6],[7],[8] However, incidence of Bipolaris and Exserohilum species together was significantly more (51%) in our study as compared to previous studies (6%–15%).[2],[18],[19]

When compared with previous studies, favorable response to medical treatment along with therapeutic debridement was obtained in (91.6%), especially in patients with anterior to mid-stromal infiltrate at initial examination.[2],[19] Therefore, early diagnosis, repeated debridement and institution of therapy with antifungal agents can lead to better prognosis.

Therapeutic penetrating keratoplasty was performed in two (3.4%) cases with perforation. Though need for keratoplasty was less as compared to other studies,[2],[5],[20] outcome of therapeutic keratoplasty was poor in our series. Both cases showed opaque graft at last follow-up. Poor outcome can be attributed to large size of grafts, inadequate clearance of infection and persistent intraocular inflammation.


  Conclusions Top


This study signifies the importance of dematiaceous fungi in the etiopathogensis of fungal keratitis. It highlights Bipolaris and Exserohilum species as emerging pathogens that were generally regarded as rare in the past. Though presence of pigmented infiltrate can be an important diagnostic clue, it is important to confirm the diagnosis through a microbiologic evaluation. Medical therapy along with debridement of ulcer alone can be effective in treating pigmented fungal keratitis in patients with superficial infiltrate who seek treatment early.

Financial support and sponsorship

This study was financially supported by Aravind Eye Hospital, Tirunelveli.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Garg P, Gopinathan U, Choudhary K, Rao GN. Keratomycosis: Clinical and microbiologic experience with dematiaceous fungi. Ophthalmology 2000;107:574-80.  Back to cited text no. 2
    
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Upadhyay MP, Karmacharya PC, Koirala S, Tuladhar NR, Bryan LE, Smolin G,et al. Epidemiologic characteristics, predisposing factors, and etiologic diagnosis of corneal ulceration in Nepal. Am J Ophthalmol 1991;111:92-9.  Back to cited text no. 9
    
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Forster RK, Rebell G, Wilson LA. Dematiaceous fungal keratitis. Clinical isolates and management. Br J Ophthalmol 1975;59:372-6.  Back to cited text no. 10
    
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Rathi H, Venugopal A, Rameshkumar G, Ramakrishnan R, Meenakshi R. Fungal keratitis caused by Exserohilum, an emerging pathogen. Cornea 2016;35:644-6.  Back to cited text no. 11
    
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Oldenburg CE, Prajna VN, Prajna L, Krishnan T, Mascarenhas J, Vaitilingam CM, et al. Clinical signs in dematiaceous and hyaline fungal keratitis. Br J Ophthalmol 2011;95:750-1.  Back to cited text no. 14
    
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Garg P, Vemuganti GK, Chatarjee S, Gopinathan U, Rao GN. Pigmented plaque presentation of dematiaceous fungal keratitis: A clinicopathologic correlation. Cornea 2004;23:571-6.  Back to cited text no. 15
    
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Chaidaroon W, Tananuvat N, Chavengsaksongkram P, Vanittanakom N. Corneal Chromoblastomycosis caused by Fonsecaea pedrosoi. Case Rep Ophthalmol 2015;6:82-7.  Back to cited text no. 16
    
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]



 

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