P176 Basidiobolus meristosporus — anew species on the block!
Authors: Chabra Ruchita , Raju S. Rajkiran , Padaki Priyadarshini , Shubha A.M. , Crasta Julian , Indumathi C , Savio Jayanthi 
Published: September 2022

Poster session 2, September 22, 2022, 12:30 PM - 1:30 PM

 

Objectives

Entomophthorales, including genus Basidiobolus, and Conidiobolus are a well-recognized cause of subcutaneous infections in immunocompetent hosts. Genus Basidiobolus is ubiquitous. All human infections except one reported so far have been due to B.ranarum.

Here we present a case of an immunocompetent 5-year-old girl with a soft tissue swelling on the right upper buttock caused by B. meristosporus.

Methods

Tissue biopsy samples from swelling over right buttock were sent for microbiological and histopathological examination. In microbiology, the samples were subjected to microscopy with Gram stain and KOH-calcofluor, aerobic, anaerobic, and fungal culture. Additionally, CBNAAT was done to rule out Mycobacterium tuberculosis. Growth on fungal culture was identified by slide culture and microscopy. The isolate was sent to PGIMER, Chandigarh for characterization using whole genome sequencing. Environmental surveillance included surveillance of soil samples from in and around the patient's house was attempted to identify the source of infection.

Results

On physical examination, an indurated mass was noted on the right lower back with a scar of a previously attempted drainage. The surface over the lesion was erythematous, the skin was scaly with no discharging sinuses.

Gram stain of the biopsy sample revealed few polymorphonuclear leukocytes and no microorganisms. KOH-calcofluor revealed broad, partially septate, hyaline fungal hyphae. Aerobic and anaerobic cultures did not yield any pathogen. CBNAAT was negative for Mycobacterium tuberculosis. Fungal culture on SDA yielded growth of waxy, expanding colonies with cerebriform center, without aerial mycelium after 72 h of incubation, at both 25°C and 37°C. LPCB mount was prepared from the primary tubes and slide culture was performed. Preliminary identification was established as B. ranarum. VITEK MS (MALDI-TOF) did not identify the isolate as this is not available in the database. Molecular characterization and phylogenetic analysis were done and the isolate was identified as B. meristosporus. Soil samples from in and around the house did not yield fungal growth morphologically resembling Basidiobolus species.

Histopathological examination of the sample revealed Splendore Hoeppli phenomenon with occasional broad, aseptate hyphae.

The child was initially treated with oral potassium iodide and later initiated on oral nitroimidazole. The response was dramatic with 70% resolution of the lesion within 3 weeks of therapy and almost complete resolution after 6 weeks. The child is on regular follow-up since then and is doing well.

Conclusion

Subcutaneous entomophthoramycosis in children are rare tropical infections that can mimic malignancy and hence are often misdiagnosed resulting in unnecessary pharmacotherapy or mutilating surgery. Diagnosis is established by isolation and correct identification of fungal species. To the best of our knowledge, only one clinical case of B. meristosporus has been reported so far. Identification of species is vital to understand factors governing pathogenicity, to establish epidemiological data, and probably revise current controversial opinions on the pathogenic species of genus Basidiobolus. Speciation based on morphology alone is unreliable and molecular methods prove useful for confirmation of species. Therefore, it is imperative that all Basidiobolus isolates are sent to referral centers for speciation to build a strong reliable database.