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| CASE REPORT |
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| Year : 2022 | Volume
: 2
| Issue : 1 | Page : 41-43 |
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Mucor keratitis versus Pythium keratitis: A clinical and microbiological dilemma
Pratima Vishwakarma1, Bhupesh Bagga1, Savitri Sharma2
1 Cornea Institute, L V Prasad Eye Institute, Hyderabad, Telangana, India
2 Jhaveri Microbiology Centre, L V Prasad Eye Institute, Hyderabad, Telangana, India
| Date of Submission | 29-Mar-2021 |
| Date of Acceptance | 12-Jul-2021 |
| Date of Web Publication | 07-Jan-2022 |
Correspondence Address:
Dr. Bhupesh Bagga
The Cornea Institute, L V Prasad Eye Institute, L V Prasad Marg, Banjara Hills, Hyderabad, Telangana - 500 034
India
 Source of Support: None, Conflict of Interest: None
DOI: 10.4103/ijo.IJO_714_21
In the pre-COVID-19 (coronavirus disease 2019) times, a 68-year-old male presented with complaints of decreased vision and whitish discoloration of the right eye. On slit-lamp examination, there was a whitish infiltrate with fuzzy margins measuring 7 mm × 6.5 mm along with <1 mm hypopyon. On microbiological examination of the corneal scraping, KOH (potassium hydroxide) + CFW (calcofluor white stain) mount revealed aseptate, broad, fungal filaments that were initially interpreted as Pythium species, but the growth on the culture was of Mucor species. The patient was managed with antifungal medications. On further follow-up, a complete resolution of the keratitis was achieved. This case highlights the importance of smear and culture correlation in such cases where the filaments of Mucor species closely mimick that of the Pythium species on microscopic examination of corneal scraping.
Keywords: Mucor keratitis, Pythium keratitis, Aseptate filaments
How to cite this article:
Vishwakarma P, Bagga B, Sharma S. Mucor keratitis versus Pythium keratitis: A clinical and microbiological dilemma. Indian J Ophthalmol Case Rep 2022;2:41-3 |
How to cite this URL:
Vishwakarma P, Bagga B, Sharma S. Mucor keratitis versus Pythium keratitis: A clinical and microbiological dilemma. Indian J Ophthalmol Case Rep [serial online] 2022 [cited 2023 Jun 2];2:41-3. Available from: https://www.ijoreports.in/text.asp?2022/2/1/41/334972 |
Keratitis caused by Mucor, a nonseptate filamentous fungus (class – Mucormycetes, order – Mucorales, and family – Mucoraceae), is a rarely reported entity.[1] Microscopically, these can be confused with Pythium.
| Case Report | |  |
A 68-year-old male presented with complaints of decreased vision (perception of hand movement) and whitish discoloration of the right eye since 2 days. Slit-lamp examination showed a 7 mm × 6.5 mm whitish corneal infiltrate with fuzzy margins and streak hypopyon [Figure 1]a. KOH (potassium hydroxide) + CFW (calcofluor white stain) mount revealed aseptate, broad, hyaline filaments with ribbon-like folds [Figure 2]a similar to the Pythium species [Figure 2]b under fluorescence microscope. Later white cottony colonies grew on blood agar and Sabouraud dextrose agar (SDA), completely filling the SDA bottle, suggestive of Mucorales [Figure 3]a, [Figure 3]b. Over 2 weeks, there were tiny gray dots on the cottony surface. Lactophenol cotton blue mount showed broad, aseptate, hyaline hyphae and sporangiophores bearing bulb-like sporangia filled with oblong spores and columella in the center and collarette at the base, consistent with the Mucor species [Figure 3]c, [Figure 3]d. Natamycin 5% eyedrops hourly and oral ketoconazole 200 mg twice daily were started. There was no COVID-19 (coronavirus disease 2019) association. Because the random blood sugar was raised (446 mg/dL), consultation of the diabetologist was taken. Visual acuity improved to 20/80 within 81 days of medical management and follow-up of 1½ years [Figure 1]b. | Figure 1: Slit-lamp picture of the cornea at the time of presentation to the clinic (a). Picture at the time of complete resolution at 1.5 years follow-up (b)
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 | Figure 2: Image of KOH + CFW mount of Mucor (a) and Pythium (b) and their differences
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 | Figure 3: White cottony colony (a) on blood agar completely filling the Sabouraud dextrose agar (b). Lactophenol cotton blue mount (c, d) shows characteristic broad aseptate hyaline hyphae and sporangiophores bearing bulb-like sporangia filled with oblong spores and columella in the center
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| Discussion | | |
Both Mucor and Pythium have broad, aseptate to sparsely septate, ribbon-like, hyaline filaments folded on themselves.[1],[2],[3] Predisposing factors for Mucormycosis include uncontrolled diabetes mellitus, several immunosuppressive conditions, iron overload, and chelation with deferoxamine; risk factors for Mucor keratitis are similar to other causes of fungal keratitis.[1] Clinically, Pythium keratitis has tentacles, a typical reticular dot-like pattern of subepithelial and superficial stromal infiltrates.[2],[4] Unlike Pythium, Mucor shows variable staining of hyphae with Grocott's methenamine silver stain.[5] Whereas Pythium shows flat, feathery-edged, partially submerged, glabrous, colorless to light-brown colonies [Figure 4],[2] Mucorales shows white, cottony, raised, lid-lifting colonies.[3] Antibacterials such as linezolid and azithromycin are required for Pythium keratitis, whereas Mucor keratitis needs antifungals such as natamycin and amphotericin B.[1],[4] | Figure 4: Flat, feathery-edged, partially submerged, glabrous, colorless to light-brown colonies of Pythium on chocolate agar
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| Conclusion | | |
The filaments of Mucor closely mimick that of Pythium sp. on microscopic examination of corneal scraping, therefore it should be confirmed in culture. This highlights the importance of smear and culture correlation in making clinical diagnosis of microbial keratitis.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
| References | | |
| 1. | Khalili MR, Abtahi SM, Atighehchian M, Hosseini S, Shirvani M, Sadeghi E, et al. Invasive fungal keratitis as an uncommon form of mucormycosis leading to endophthalmitis: Report of two cases and literature review. Curr Fungal Infect Rep 2020;14:384-90.  |
| 2. | Sharma S, Balne PK, Motukupally SR, Das S, Garg P, Sahu SK, et al. Pythium insidiosum keratitis: Clinical profile and role of DNA sequencing and zoospore formation in diagnosis. Cornea 2015;34:438-42. |
| 3. | Lass-Florl C. Zygomycosis: Conventional laboratory diagnosis. Clin Microbiol Infect 2009;15(Suppl 5):60-5. |
| 4. | Bagga B, Sharma S, Madhuri Guda SJ, Nagpal R, Joseph J, Manjulatha K, et al. Leap forward in the treatment of Pythium insidiosum keratitis. Br J Ophthalmol 2018;102:1629-33. |
| 5. | Guarner J, Brandt ME. Histopathologic diagnosis of fungal infections in the 21 st century. Clin Microbiol Rev 2011;24:247-80. |
[Figure 1], [Figure 2], [Figure 3], [Figure 4]
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