Phylogenetic analysis reveals two genotypes of the emerging fungus Mucor indicus, an opportunistic human pathogen in immunocompromised patients

Abstract

Mucormycosis is a rare fungal infection caused by Mucor indicus. Phylogenetic analysis of many M. indicus isolates, mainly sampled from different clinical and environmental specimens collected worldwide, revealed two genotypes, I and II, based on ITS and D1/D2 LSU rDNA sequences. A retrospective review of the literature revealed 13 cases. Eight (76.9%) patients had disseminated infections, and the overall mortality rate was 30.7%. A pulmonary infection caused by M. indicus genotype I in a liver transplant recipient was disseminated to include the skin and was successfully treated with liposomal amphotericin B and aggressive surgery. M. indicus can infect a wide variety of patients with no real preference for the site of infection. We concluded that M. indicus has emerged as a significant cause of invasive mycosis in severely immunocompromised patients worldwide. Early diagnosis and initiation of appropriate therapy could enhance survival in these immunocompromised patient populations.

Figure 1

Imaging of the chest. (A) X-ray showing the thick-walled cavity (fungal mass) at the base of the right upper lobe. (B) A high-resolution CT scan shows bilateral opacities.

Figure 2

Necrotic ulcer of the skin above the knee with excessive redness and swelling around the wound.

Figure 3

Dissemination of fungal hyphae of M. indicus into the tissue of the skin ulcer showed ribbon-like, right-angle branching hyphae. (A) Fungal hyphae (arrow) in skin tissue stained with hematoxylin and eosin (× 400), bar=10 μm. (B) Darkly stained right-angle branched hyphae of M. indicus (arrow) on a green-stained cellular background as seen in histological sections of the skin tissue of the ulcer showed blood vessel invasion. Stained with Gomori methenamine silver (× 200), bar=20 μm.

Figure 4

Phylogenetic ML tree with 1000 bootstrap replications. (A) Based on the ITS1, 5.8S, and ITS2 regions of the ribosomal DNA. The scale bar indicates 0.02 substitutions per site. (B) Based on the D1/D2 region of the large subunit of the ribosomal DNA. The scale bar indicates 0.01 substitutions per site. Accession numbers in bold are sequences created in this study.