| Abstract|| |
Basidiobolus ranarum is an uncommon pathogen in ocular infections. It has been previously reported from subcutaneous and gastrointestinal infections. Here, we report a rare case of ocular infection caused by B. ranarum. A 21-year-old male patient presented with visual loss and pain in the right eye due to corneal abscess following an injury while welding. KOH mount performed was indicative of fungal hyphae. Fungal culture revealed growth of B. ranarum. Meanwhile, the patient was treated with antifungal (topical natamycin and oral ketoconazole) along with total corneal transplantation. B. ranarum is a fungus very uncommonly causing ocular pathogenesis. This results in diagnostic confusion leading to poor treatment outcomes. Hence, a mycology laboratory has to be aware about this fungus and need to consider it as a differential diagnosis in patients with infectious corneal abscess.
Keywords: Basidiobolus ranarum, corneal ulcer, ocular basidiobolomycosis
|How to cite this article:|
Baradkar V, Chatterjee N, Shastri JS, Vedpathak MU. Ocular basidiobolomycosis – Rare presentation: A case report. Indian J Pathol Microbiol 2020;63:270-2
|How to cite this URL:|
Baradkar V, Chatterjee N, Shastri JS, Vedpathak MU. Ocular basidiobolomycosis – Rare presentation: A case report. Indian J Pathol Microbiol [serial online] 2020 [cited 2021 Apr 23];63:270-2. Available from: https://www.ijpmonline.org/text.asp?2020/63/2/270/282709
| Introduction|| |
Basidiobolus ranarum is a filamentous fungus which belongs to the subphylum Entomophthoromicotina under phylum Glomeromycota. It has a worldwide distribution. It was first isolated in 1886 by Eidam. Infections are generally geographically limited to tropical and subtropical regions such as East and West Africa.B. ranarum is known mostly as a cause of subcutaneous and gastrointestinal manifestations., There is usually a granulomatous infection in an immunocompetant host, with a male preponderance.
There are very few published reports of Basidobolus infections including one from India causing ocular infection. This is a case report of a 21-year-old male patient who suffered from corneal ulcer due to this fungus.
| Case History|| |
A 21-year-old male patient came to the outpatient department of ophthalmology with complaints of pain, watering, swelling, and decrease of vision in the right eye since 10 days. The patient gave history of a foreign body injury in the right eye during welding 15 days ago. There was no history of surgical intervention, trauma to the other eye, diplopia, discharge, drug allergy, diabetes, and immunocompromising disease or drug intake. The left eye was normal.
On examination, there was a whitish opacity in the right eye along with corneal abscess with an impregnated foreign body in the right eye as shown in [Figure 1]a. Conjunctival congestion and lid edema were noted. In the anterior chamber, there was collection of pus and lens was also involved, though there was no corneal perforation. Intraocular pressure was normal. Best-corrected visual acuity was restricted to perception and projection of light normal in all quadrants. The left eye was normal on examination. General blood investigations revealed total leukocyte count of 14,600/mm3, neutrophils 82.4%, lymphocytes 16.7%, hemoglobin 12.3 g/dL, routine blood sugar 86 mg/dL, and HbA1c 4.6 g/dL.
|Figure 1: (a) Corneal abscess with white opacity in the left eye (b) KOH mount showing asepate hyphae |
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Initially, the patient was treated with antibacterial agent, namely, gentamicin eye drop, but the patient did not respond well, so 3 days later antifungal agents as eye drop (natamycin) and oral (fluconazole) were also added to the regimen. The patient was further posted for total corneal replacement with donor tissue along with anterior chamber and lens aspiration. He responded well to this intervention. The infected corneal button was sent in a sterile container to the microbiology department for pathogen identification.
The corneal button was put on a sterile slide in a sterile Petridish and with the help of sterile forceps and sterile blade; the corneal button was cut into pieces. While cutting, some material from the corneal button was spread over the slide for Gram stain. One piece was used for bacteriological culture, one was put in 40% potassium hydroxide (KOH), and the remaining one was subcultured in Sabouraud's dextrose agar (SDA) in a tube without antibiotics.
The KOH mount showed aseptate hyphae as shown in [Figure 1]b. Bacterial culture was negative.
On SDA agar within 4–5 days, colonies were flat, whitish-grey with pale reverse with white powdery deposit all over the tube as shown in [Figure 2]a. Microscopic examination showed plenty of zygospores. Later, the colony became radiated and folded with waxy texture. Lactophenol cotton blue (LPCB) tease mount from the culture showed aseptate hyphae with typical smooth-walled zygospore observed with two closely appressed beak-shaped gametangeal remnants of copulation tube as depicted in [Figure 3]a. The colony was also subcultured on the SDA plate and the satellite colonies were seen [Figure 2]b and [Figure 2]c.
|Figure 2: (a) Flat, whitish-grey growth on SDA slant. (b) Young (48-h) individual colony on SDA plate. (c) Old (7 days) satellite colony on SDA plate|
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|Figure 3: (a) Aseptate hyphae with smooth walled zygospore with two closely appressed beak shaped gametangeal remnants on LPCB mount from teased culture & (b) slide culture |
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Slide culture was done on potato dextrose agar. On slide culture, non-septate broad hyphae were seen with zygospores, which had a thin outer wall, foamy cytoplasm, and a nucleus containing a large nucleolus with typically characteristic conjugation beaks as shown in [Figure 3]b. The isolate also produced a large number of asexual spores, which were characterized by the presence of a hyphal tag or cleavage formation to produce meristospores.
The clinician was informed about the fungus and the patient was treated with oral potassium iodide and itraconazole eye drop. He responded well and was discharged on day 12 with those antifungal drugs.
| Discussion|| |
Lei-Kian Joe from Indonesia in 1956 first described the human infection of B. ranarum. The literal meaning of the word entomopthoromycosis in Greek is insect eater which gives the habitat of this fungus, that is, gastrointestinal tracts of insects. Along with that, it also stays in soil, decaying vegetation and gastrointestinal tracts of amphibians. Usually, the mode of transmission is insect bite or minor trauma. The order Entomophthorale shares the position with Mucorales as a part of zygomycete. The difference is Mucorales mostly affects the immunocompromised hosts, while Entomophthorales have the capacity to affect the immunocompetent individuals.
To date, worldwide, there are around 250 reported cases caused by Basidiobolus. All of them are mostly isolated and reported from subcutaneous or gastrointestinal infective sources. There are only a few reported cases worldwide of B. ranarum causing ocular infection. One case of giant orbitofacial basidiobolomycosis was reported from the northern part of Nigeria. Similarly, a case of keratitis with endophthalmitis in case series of fungal keratitis was reported from Saudi Arabia. Tananuvat et al. from Thailand reported a case of scleritis. From India, there is only one published report of Basidiobolus causing postoperative fungal endophthalmitis. This case of ocular basidiobolomycosis is being reported due to the isolation of a rare and unique species of fungus, first time from India, as a causative agent of corneal abscess. The causative agent probably entered through the trauma. The patient was first treated for bacterial keratitis but finally had to be managed by surgical intervention and antifungal agents. This fungus can produce lipase and protease after infection which hydrolyses fat and protein constituents of the tissue. These enzymes help in invasion into deeper tissue. This was the probable reason in this patient having anterior chamber and lens involvement even if there was no corneal perforation.
The basic difference between the presentation of this fungus causing a subcutaneous and an ocular infection is that in subcutaneous infection it is a typical presentation with slow-growing, nodular granuloma formation with Splendore–Hoeppli phenomenon showing in histopathological slide with hematoxylin and eosin (H and E) staining, in contrast to ophthalmic infections. It is very difficult to predict this fungus from clinical presentation as it simulates scleritis or ophthalmitis due to any other cause. Hence, it is very important to get a rapid and definitive laboratory diagnosis of this fungus for a favorable outcome.
Timely treatment is very essential for this fungus for a better prognosis. A combination of a saturated solution of potassium iodide and oral itraconazole is very effective for subcutaneous infection. But there is no study on the treatment protocol of ocular infection by this fungus. In our case report, the patient seemed to respond to oral and topical antifungal agents along with surgical intervention.
| Conclusion|| |
B. ranarum is not a rare fungus, but its association with ocular pathogenesis is very uncommon and ambiguous with regard to its deceptive presentation. As the clinical scenario of ocular basidiobolomycosis may resemble other infections, knowledge of this rare differential diagnosis will help clinicians in effective diagnosis and treatment.
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.
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Conflicts of interest
There are no conflicts of interest.
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Department of Microbiology, College Building, 3rd Floor, TNMC and BYL Nair Charitable Hospital, A L Nair Road, Mumbai Central, Mumbai - 400 008, Maharashtra
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3]