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  Table of Contents  
CASE REPORT
Year : 2018  |  Volume : 36  |  Issue : 4  |  Page : 594-596
 

Fungal keratitis caused by Podospora austroamericana: A first case report


1 Department of Ocular Microbiology, Aravind Eye Hospital and Post Graduate Institute of Ophthalmology, Madurai, Tamil Nadu, India
2 Department of Intraocular Lens and Cataract Services, Aravind Eye Hospital and Post Graduate Institute of Ophthalmology, Madurai, Tamil Nadu, India
3 Department of Cornea and Refractive Surgery Services, Aravind Eye Hospital and Post Graduate Institute of Ophthalmology, Madurai, Tamil Nadu, India

Date of Web Publication18-Mar-2019

Correspondence Address:
Dr. Prajna Lalitha
Department of Ocular Microbiology, Aravind Eye Hospital and Post Graduate Institute of Ophthalmology, No. 1, Anna Nagar, Madurai - 625 020, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijmm.IJMM_19_1

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 ~ Abstract 

We report a case of keratitis caused by a rare fungus Podospora austroamericana. Clinical and microbiological evaluation of the corneal ulcer was done and the treatment outcome was studied. The fungus was grown from the corneal scraping, and it was identified as P. austroamericana based on DNA sequence and analysis of the internal transcribed spacer region. The patient was treated with topical azithromycin, natamycin and voriconazole. Despite maximum medical therapy, the ulcer progressed very rapidly and the patient developed panophthalmitis and evisceration of the eye had to be done. This is the first reported case of keratitis caused by P. austroamericana.


Keywords: DNA sequencing, keratitis, panophthalmitis, polymerase chain reaction


How to cite this article:
Rameshkumar G, Ponlakshmi M, Selvapandiyan A, Ramsudharsan R, Krishnan RS, Lalitha P. Fungal keratitis caused by Podospora austroamericana: A first case report. Indian J Med Microbiol 2018;36:594-6

How to cite this URL:
Rameshkumar G, Ponlakshmi M, Selvapandiyan A, Ramsudharsan R, Krishnan RS, Lalitha P. Fungal keratitis caused by Podospora austroamericana: A first case report. Indian J Med Microbiol [serial online] 2018 [cited 2019 Sep 18];36:594-6. Available from: http://www.ijmm.org/text.asp?2018/36/4/594/254405



 ~ Introduction Top


Fungal keratitis is an important cause of visual loss globally. The fungi implicated appear to vary depending on the geographical locations. Fusarium spp. and Aspergillus spp. are the most prevalent fungus causing mycotic keratitis in South India.[1],[2] However, various rare fungi causing mycotic keratitis have been reported from different parts of India.[3] Podospora austroamericana is a plant pathogen. Podospora is a ubiquitous genus in the family Lasiosphaeriaceae (Ascomycota and fungi) and now includes approximately 78 species.[4] The Podospora species is reported mainly from soil [5] and cow dung.[6] We report a case of keratitis caused by P. austroamericana and discuss the presentation, identification of the fungus and the management.


 ~ Case Report Top


A 65-year-old male presented with redness and pain in his right eye 4 days after undergoing cataract surgery. He did not recall any history of ocular trauma or fall of foreign body. He did not have any other systemic complaints. On examination, his visual acuity in the right eye was only perception of light. The conjunctiva was congested and lid edema was seen. The cornea had a circumcorneal congestion, multiple stromal infiltrates along the limbus with diffuse stromal oedema [Figure 1]a. As per our clinical protocol, the ulcer was scraped using a Kimura spatula and subjected to microbiological evaluation which included smear and culture methods. The smears employed were Gram staining and 10% potassium hydroxide (KOH) mount, while the culture methods included blood agar and potato dextrose agar. The Gram stain and 10% KOH mount showed the presence of filamentous fungi [Figure 2]a. Colonies were pale white in colour and velvety in nature in front [Figure 2]b. Spore morphology was identified using lactophenol cotton blue mounting, but the fungus could not identified using conventional techniques due to lack of sporulation even after 2–3 weeks of incubation. After 4 weeks of incubation, the ascospore morphology was identified and presented in [Figure 2]c, [Figure 2]d, [Figure 2]e. DNA extraction from the fungus was carried out using the phenol–chloroform method. Polymerase chain reaction (PCR) targeting the internal transcribed spacer (ITS) region 1 and 4 was carried out in 50 μl reactions, containing 1 μl of 200 mM dNTPs, 5 μl of reaction buffer (Tris with Mgcl2), 10 pM forward primer (ITS 1: 5' TCCGTAGGTGAACCTGCGG 3') and reverse primer (ITS4:5' TCCTCCGCTTATTGATATG 3'),[7] 1.2 U/μl of Taq polymerase and 5 μl of genomic DNA, and amplification was carried out in Agilent SureCycler 8800 (Agilent Technologies, USA). DNA sequencing was done using an ABI 3100 genetic analyzer (PE Applied Biosystems, Foster City, CA, USA). The sequence was analysed and identified using MegaBlast search programme of GenBank database. The query coverage and identity were 100%. The sequence was submitted in NCBI (GenBank Accession number: MH973201).In vitro antifungal susceptibility testing was performed by broth microdilution method (CLSI guidelines M38A2) against following drugs: amphotericin B, voriconazole, ketoconazole, posaconazole, natamycin and caspofungin.[8] The organism was susceptible to all the antifungal drugs [Table 1]. The patient was started with topical azithromycin (1%), natamycin (5%) and voriconazole (1%) hourly with atropine eye drops and painkillers. He was reviewed daily. The size of stromal infiltrate increased despite active treatment. Hence, itraconozole eye drops and oral ketoconazole 200 mg bd were also added. Azithromycin (1%) was added as the clinical picture was thought to resemble Pythium keratitis. However, the eye became phthisical within 4 weeks and nothing further could be done to restore the vision [Figure 1]b.
Figure 1: Clinical findings of patients with Podospora austroamericana keratitis. (a) Slit-lamp picture of the cornea showing multifocal anterior stromal infiltrate. (b) Total limbus-to-limbus full-thickness infiltrate

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Figure 2: (a) Gram-stain image showing septate fungal hyphae seen under ×100. (b) Pale white colour fungus grown in potato dextrose agar plate after 3 days of incubation at 27°C. (c) Ascoma of Podospora austroamericana. (d) Asci with ascospores. (e) Ascospores

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Table 1: Antifungal susceptibilities of the clinical isolate of Podospora austroamericana

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 ~ Discussion Top


Fungal keratitis is a major public health problem in India and other developing countries. Fusarium and Aspergillus species are the commonly reported major pathogens in most of the geographical areas.[1],[2],[3] The Podospora species is a large and polymorphic genus. There is notable variation in the structure, especially ascomatal wall and ascospore appendages. Mirza and Cain revised the genus of these fungi and listed 64 species [5] and Lundqvist (1972) who reviewed the Nordic coprophilous species re-introduced the genus Schizothecium corda and transferring 31 species of Podospora to it. He re-established the relationship between these two species based on the spore morphology.[9] Podospora species are mostly coprophilic in habit and also reported as plant pathogen.[5],[6] In our case report, the patient did not recall any history of ocular trauma. However, the possibility of a trivial ocular trauma cannot be ruled out. The case described in this report deserves attention because of the unique characteristics of the organism, difficulties in identification and non-responsive to treatment. There is no clinical information in the medical literature concerning Podospora species because it has not been identified in clinical samples in the previous reports and is unreported in ocular infections.

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 Top

1.
Lalitha P, Prajna NV, Manoharan G, Srinivasan M, Mascarenhas J, Das M, et al. Trends in bacterial and fungal keratitis in South India, 2002-2012. Br J Ophthalmol 2015;99:192-4.  Back to cited text no. 1
    
2.
Sengupta S, Rajan S, Reddy PR, Thiruvengadakrishnan K, Ravindran RD, Lalitha P, et al. Comparative study on the incidence and outcomes of pigmented versus non pigmented keratomycosis. Indian J Ophthalmol 2011;59:291-6.  Back to cited text no. 2
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3.
Saha S, Banerjee D, Khetan A, Sengupta J. Epidemiological profile of fungal keratitis in urban population of West Bengal, India. Oman J Ophthalmol 2009;2:114-8.  Back to cited text no. 3
[PUBMED]  [Full text]  
4.
Cai L, Jeewon R, Hyde KD. Phylogenetic evaluation and taxonomic revision of Schizothecium based on ribosomal DNA and protein coding genes. Fungal Divers 2005;19:1-17.  Back to cited text no. 4
    
5.
Stchigel AM, Calduch M, Guarro J, Zaror L. A new species of Podospora from soil in Chile. Mycologia 2002;94:554-8.  Back to cited text no. 5
    
6.
Mirza JH, Cain RF. Revision of the genus Podospora. Can J Bot 1969;47:1999-2048.  Back to cited text no. 6
    
7.
Jaeger EE, Carroll NM, Choudhury S, Dunlop AA, Towler HM, Matheson MM, et al. Rapid detection and identification of Candida, Aspergillus and Fusarium species in ocular samples using nested PCR. J Clin Microbiol 2000;38:2902-8.  Back to cited text no. 7
    
8.
Clinical and Laboratory Standards Institute. Reference Method for Broth Dilution Antifungal Susceptibility Testing of Filamentous Fungi; Approved Standard. CLSI Document M38-A2. 2nd ed. Wayne, PA: Clinical and Laboratory Standards Institute; 2008.  Back to cited text no. 8
    
9.
Lundqvist N. Nordic Sordariaceae s. lat. Symb Bot Ups 1972;20:1-374.  Back to cited text no. 9
    


    Figures

  [Figure 1], [Figure 2]
 
 
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