|Year : 2012 | Volume
| Issue : 3 | Page : 361-363
A rare case of human mycosis by Rhizoctonia solani
NM Kaore, AR Atul, MZ Khan, VK Ramnani
Department of Microbiology, Peoples College of Medical Sciences and RC, Bhanpur Road, Bhopal, Madhya Pradesh, India
|Date of Submission||18-Jan-2012|
|Date of Acceptance||30-Mar-2012|
|Date of Web Publication||8-Aug-2012|
N M Kaore
Department of Microbiology, Peoples College of Medical Sciences and RC, Bhanpur Road, Bhopal, Madhya Pradesh
Source of Support: None, Conflict of Interest: None
Rhizoctonia solani is a most widely recognized strong saprophyte with a great diversity of host plants. It is a first ever case of extensive human mycosis caused by Rhizoctonia solani in a 65-year-old diabetic and hypertensive farmer, with a history of head injury caused by fall of mud wall. Necrotic material collected revealed septate fungal hyphae with bacterial co-infection. Fungal culture on SDA at 25°C showed cotton wooly growth progressing to greyish-white to shiny metallic black colonies and identified on basis of septate mycelial growth without conidia, right angle branching, presence of compact hyphal forms and anastomosis between branching hyphae on LPCB mount.
Keywords: Rhizoctonia solani, human mycosis, rare case
|How to cite this article:|
Kaore N M, Atul A R, Khan M Z, Ramnani V K. A rare case of human mycosis by Rhizoctonia solani. Indian J Med Microbiol 2012;30:361-3
|How to cite this URL:|
Kaore N M, Atul A R, Khan M Z, Ramnani V K. A rare case of human mycosis by Rhizoctonia solani. Indian J Med Microbiol [serial online] 2012 [cited 2019 Aug 20];30:361-3. Available from: http://www.ijmm.org/text.asp?2012/30/3/361/99508
| ~ Introduction|| |
Rhizoctonia solani is a most widely recognized strong saprophyte with a great diversity of host plants being able to survive for extended periods of time in the absence of living host plants by feeding on decaying organic matter. Keratitis caused by accidental inoculation had been reported previously, but extensive human mycosis with necrosis, myositis and invasive lesions has not been reported earlier. 
| ~ Case Report|| |
A 65-year-old male, farmer by profession was admitted to medical ICU of with head injury, reported to be caused by collapse of mud wall of the house he used to reside without loss of consciousness, vomiting or convulsions. CT scan revealed fracture of zygomatic arch and maxillary sinus wall with fracture of bony part of external auditory canal on left side. Patient was hypertensive with uncontrolled diabetes and deteriorated steadily with loss of consciousness and severe myositis and necrotic lesion on left side of face. Pus discharge from the lesion and left ear was cultured aerobically yielding Klebsiella pneumoniae, whereas CSF sample cultured yielded E. coli. The necrotic lesion progressed further even with antibiotic coverage over the next 5 days. Extensive debridement was done, and samples from lateral, medial and orbital margins were sent to Department of Microbiology, for KOH mount and fungal culture suspecting rhinocerebral mucormycosis.
| ~ Mycological Study and Diagnosis|| |
The KOH mounts of the necrotic material were observed, which revealed the presence of septate mycelium and were reported to treating physicians [Figure 1] and the patient was put on Fluconazole. The necrotic material was inoculated directly onto Sabouraud Dextrose Agar (SDA) from HiMedia India, and incubated at 25 and 37°C. After 4 days of incubation at room temperature, cotton wooly growth appeared on the SDA, which turned greyish black on further incubation of 10 days. The reverse appeared off white to tan with slight wrinkles. The growth progressed to jet black coloured colonies with metallic shin over next 10 days. [Figure 2] and [Figure 3]
|Figure 2: Growth of Rhizoctonia after 14 days showing greyish white colonies|
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|Figure 3: Growth of Rhizoctonia after 24 days showing Jet black colonies|
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Lacto Phenol Cotton Blue (LPCB) mount of the colonies showed septate hyphae with no conidia. The hyphae produce branches at right angles and acute angles to main hypha with slight constriction at the site of origin. [Figure 4] The specialised compact hypheal forms were also seen along with the dividing hyphae, which fused together to form anastomosis. The fungus was identified as Rhizoctonia species based on the optimal growth at 25°C without conidia, right angle branching, presence of compact hypheal forms and anastomosis between branching hyphae. The fungal isolate was subcultured on SDA and sent for confirmation to Research Centre for Human Mycoses and Allergy, Lucknow and was reconfirmed to be Rhizoctonia solani.
With antimicrobials, CSF culture was sterile, but patients conditioned remained static with fluconazole as an anti-fungal agent. With an initiation of Amphotericin-B, patient brought a remarkable improvement and was later operated with removal of zygomatic arch with hemimaxillectomy and enucleation, leading to complete recovery.
|Figure 4: LPCB mount from slide culture showing right angle branching, compact hypheal forms and anastomosis|
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| ~ Discussion|| |
Rhizoctonia solani, the most widely recognized species of Rhizoctonia, was originally described by Julius Kühn on potato in 1858. R. solani is a very common soil-borne pathogen with a great diversity of host plants. It belongs to phylum Basidiomycota, Class Agaricomycetes, Order Cantharellales, Family Ceratobasidiaceae and Genus Rhizoctonia. Rhizoctonia solani is a basidiomycete fungus that does not produce any asexual spores (called conidia) and only occasionally produces sexual spores (basidiospores). The vegetative mycelium of R. solani and other Rhizoctonia fungi are colourless when young but become brown-coloured as they grow and mature. Because Rhizoctonia species often do not produce spores, these fungi are identified by characteristics of their hyphae. Rhizoctonia hyphae produce branches at right and acute angles to the main hypha and usually possess more than 3 nuclei per hyphal cell. The branch hypha is slightly constricted at the branch origin, and there is often a septum near the branch origin. Rhizoctonia species also produce specialized hyphae composed of compact cells called monilioid cells. The monilioid cells fuse together to produce hard structures called sclerotia, which are resistant to environmental extremes, allowing the fungus to survive adverse conditions. Species of Rhizoctonia are further divided into groups based on the ability of hyphae to fuse with one another, a phenomenon known as anastomosis. Anastomosis is the primary means of genetic recombination in Rhizoctonia, therefore, isolates within an anastomosis group (AG) are closely related to one another. ,
Rhizoctonia solani forms colonies on potato dextrose agar (PDA) that range in colour from buff to black. Sclerotia are produced on the surface of cultures after 4 to 6 weeks, and are irregularly shaped, light tan to black, and usually > 1 mm (0.04 in.) in width. The optimum temperature for growth of R. solani in pure culture ranges from 18°C to 28°C. This species is divided into 11 AGs.
Rhizoctonia species are strong saprophyte, able to survive for extended periods of time in the absence of living host plants by feeding on decaying organic matter. When conditions are not favourable for growth, these fungi persist as mycelium or as sclerotia in the thatch and soil. When a host plant is present and environmental conditions are favourable, Rhizoctonia species begin to colonise the surface of the potential host plant with long, unbranched hyphae called runner hyphae. Depending on the isolate and host species, the runner hyphae may branch and penetrate through stomata or give rise to structures called infection cushions, which are aggregates of convoluted hyphae. The infection cushions are involved in enzymatic degradation and physical penetration of the leaf surface, providing entrance into the plant for the pathogen. ,
Human infections caused by Rhizoctonia are very rare, and first case report of keratitis by Rhizactonia was reported way back in 1977. 
The case discussed here is diabetic patient with a rural background and farmer by profession with a severe facial injury because of falling mud wall, which might be the cause of initial inoculum from the soil. Old age, uncontrolled diabetes and immune-suppressed status after an admission might have given a saprophyte to grow in the lesion. To the best of our knowledge, this is the first ever case report of a well-known plant pathogen and a saprophyte causing human mycosis.
| ~ Acknowledgment|| |
We thank Dr. Ashok K. Srivastava, Medical Mycologist And Director, Research Center for Human Mycoses and Allergy Lucknow for processing the sample and confirming it to be Rhizoctonia solani.
| ~ References|| |
|1.||Srivastava OP, Lal B, Agrawal PK, Agarwal SC, Chandra B, Mathur IS. Mycotic keratitis due to Rhizoctonia sp. Sabouraudia 1977;15:125-31. |
|2.||Anderson NA. The Genetics and Pathology of Rhizoctonia Solani. Annu Rev Phytopathol 1982;20:329-47. |
|3.||Gracia VG, Onco MAP, Susan VR. Review, Biology and Systematics of the form genus Rhizoctonia. Span J Agric Res 2006;4:55-79. |
|4.||Tsror L. Biology, Epidemiology and Management of Rhizoctonia solani on Potato. J Phytopathol 2010;158:649-58. |
[Figure 1], [Figure 2], [Figure 3], [Figure 4]