Saksenaea dorisiae sp. nov., a New Opportunistic Pathogenic Fungus from Europe

Abstract

A new species, Saksenaea dorisiae (Mucoromycotina, Mucorales), isolated from a water sample originating from a private well in Manastirica, Petrovac, in the Republic of Serbia (Europe), is described and illustrated. The new taxon is well supported by multilocus phylogenetic analysis that included the internal transcribed spacer (ITS) region, domains D1 and D2 of the 28S rRNA gene (LSU), and translation elongation factor-1α gene (tef-1α), and it is resolved in a clade with S. oblongispora and S. trapezispora. This fungus is characterized by its moderately slow growth at 15 and 37°C, sparse rhizoids, conical-shaped sporangia, and short-cylindrical sporangiospores. Saksenaea dorisiae is a member of the opportunistic pathogenic genus often involved in severe human and animal mucormycoses encountered in tropical and subtropical regions. Despite its sensitivity to several conventional antifungals (terbinafine and ciclopirox), the fungus can potentially evoke clinically challenging infections. This is the first novel taxon of the genus Saksenaea described from the moderately continental climate area of Europe.

Figure 1

Maximum Likelihood tree based on a concatenated set of 3 sequences (ITS, LSU, and tef-1α) for the new taxon S. dorisiae is compared with species from the same genus Saksenaea. Numbers at nodes indicate bootstrap values (expressed as percentages of 1000 replications). Apophysomyces elegans CBS 476.78 was used as an outgroup. Scale bar indicates 0.02 substitutions per nucleotide position. S = Saksenaea, A = Apophysomyces; ^Tex-type strain. New species is in bold.

Figure 2

Saksenaea dorisiae (BiMM-F232). Colonies on CZA and MEA (4 days old) at 35 (a) and 37°C (b).

Figure 3

Saksenaea dorisiae (BiMM-F232). (a)–(e) Sporangiophores with sporangia (on CZA, 6 days old). (f)–(h) Young sporangia with rounded neck (closed). (i) Details of asperulate sporangiophore (on CZA, 6 days old). (j)–(l) Sporangiospores and details of sporangial neck (on CZA, 6 days old). Scale bars = 500 μm (a), 50 μm (b)–(g), 10 μm (h)–(l).

Figure 4

Line drawing of micromorphology of Saksenaea dorisiae (BiMM-F232). (a, b, and c) sporangiophores, sporangia, and sporangiospores on CZA (6–8 days old). (a) Sporangiophores with sporangium and mature sporangiospores. (b) Sporangiophores with sporangia (in situ). (c) Sporangiospores. (a, b) Scale bar = 50 μm; (c) scale bar = 5 μm.

Figure 5

In vitro antifungal susceptibility of Saksenaea dorisiae BiMM-F232 towards selected antifungals after 3 days incubation at 37°C. MIC Test strips: (a) posaconazole (POS), (b) itraconazole (ITC), (c) ketoconazole (KE), (d) caspofungin (CAS), (e) flucytosine (FC),(f) fluconazole (FLU), (g) voriconazole (VO), (h) amphotericin B (AMB), and (i) antifungal discs(left top to left bottom: ketoconazole KCA 15 μg and itraconazole ITC 8 and 15 μg; right top to right bottom: clotrimazole CLO 50 μm and fluconazole FLU 25 and 100 μm); all plates were overgrown by the fungus after prolonged incubation (5 days) at 37°C.