Reclassification of the Candida haemulonii Complex as Candida haemulonii (C. haemulonii Group I), C. duobushaemulonii sp. nov. (C. haemulonii Group II), and C. haemulonii var. vulnera var. nov.: Three Multiresistant Human Pathogenic Yeasts

Abstract

dThe Candida haemulonii species complex is currently known as C. haemulonii groups I and II. Here we describe C. haemulonii group II as a new species, Candida duobushaemulonii sp. nov., and C. haemulonii var. vulnera as new a variety of C. haemulonii group I using phenotypic and molecular methods. These taxa and other relatives of C. haemulonii (i.e., Candida auris and Candida pseudohaemulonii) cannot be differentiated by the commercial methods now used for yeast identification. Four isolates (C. haemulonii var. vulnera) differed from the other isolates of C. haemulonii in the sequence of the internal transcribed spacer (ITS) regions of the nuclear rRNA gene operon. The new species and the new variety have a multiresistant antifungal profile, which includes high MICs of amphotericin B (geometric mean MIC, 1.18 mg/liter for C. haemulonii var. vulnera and 2 mg/liter for C. duobushaemulonii sp. nov) and cross-resistance to azole compounds. Identification of these species should be based on molecular methods, such as sequence analysis of ITS regions and matrix-assisted laser desorption ionization-time of flight mass spectrometry. Candida and Aspergillus species are the most common causes of invasive fungal infections in immunocompromised individuals, but besides these fungi, many other yeast species and filamentous fungi can be pathogenic in such individuals (7). The list of reported species that cause human infection is constantly growing, partly because of recent advances in molecular tools and diagnostics. Thus, new clinically relevant species such as Candida metapsilosis, Candida orthopsilosis, Candida bracariensis, and Candida nivariensis, have been described recently (1,5,39).Candida haemulonii (van Uden and Kolipinsky) S. A. Meyer and D. Yarrow (41) (syn. Torulopsis haemulonii) is one of the rare yeast species that can be isolated from human clinical sources. The species originally described was from the gut of a blue-striped grunt fish (Haemulon scirus) in 1962 (40). The first isolation of this yeast from a human, i.e., from the blood of a patient with renal failure, was reported by Lavarde et al. (22). Since then, several cases of infections due to this yeast have been described in the literature, varying from superficial to deep infections. Cases of catheter-related fungemia (18), bloodstream infections (30,34), and osteitis (6) and outbreaks in intensive care units (16) have been reported recently. The species has also been isolated from toenails of diabetic patients (13). Noteworthy is the susceptibility profile of this yeast, which shows high MICs of amphotericin B (AMB) and fluconazole (FLC) (ranges, 0.5 to 32 and 4 to Ͼ64 mg/liter, respectively), which can hinder the management of patients with deep infections caused by this yeast. This antifungal profile has often been associated with clinical failure (6,16,17,30,34).The C. haemulonii species complex was further studied by Lehman et al. in 1993 (24). They studied 25 strains from different geographic origins and clinical sources and described two gene...

Identification and Antifungal Susceptibility Profiles of Candida haemulonii Species Complex Clinical Isolates from a Multicenter Study in China

“…Their differentiation relies on molecular methods with good discrimination to the species and varietal or intraspecies levels, such as sequence analysis of the ribosomal DNA (rDNA) internal transcribed spacer (ITS) genes. The use of ITS sequencing (considered the reference method) together with matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) may provide improved discrimination of members of this complex for reference spectra that are contained within the used MS database (8,9). In contrast, phenotypic identification methods, such as the API 20C and Vitek yeast identification systems (bioMérieux, Marcy l'Etoile, France), typically lead to errors in identification (10,11).…”

“…Members of this species complex can be divided into three genotypically distinguishable species: C. haemulonii, C. haemulonii var. vulnera, and C. duobushaemulonii (8). Their differentiation relies on molecular methods with good discrimination to the species and varietal or intraspecies levels, such as sequence analysis of the ribosomal DNA (rDNA) internal transcribed spacer (ITS) genes.…”

Rare occurrence of fatalCandida haemuloniiperitonitis in a diabetic CAPD patient

“…The species has also been isolated from toe nails of diabetic patients. 5 In another Indian study, the incidence of fungal peritonitis was 16.2% with mortality in 20%. 6 This patient did not have risk factors for fungal peritonitis and had no exit site infection.…”

“…Noteworthy is the susceptibility profile of this yeast that shows high minimal inhibitory concentrations (MIC) for amphotericin B (AMB) and fluconazole (FLC) (range 0.5-32; mg/L and 4-464; mg/L, respectively), which can hinder the management of patients with deep infections caused by this yeast. 5 Candida haemulonii is one of the rare yeast species that can be isolated from 49 human clinical sources. The first isolation of this yeast from humans was reported from the blood of a patient with renal failure.…”

Development of Two Molecular Approaches for Differentiation of Clinically Relevant Yeast Species Closely Related to Candida guilliermondii and Candida famata

“…These closely related species actually belong to diverse species complexes, as revealed by sequence and phylogenetic analyses. Recent advances in molecular techniques have allowed differentiation of these species complexes, such as the Candida albicans complex composed of C. albicans, Candida dubliniensis, Candida africana, and Candida stellatoidea type I, the Candida parapsilosis complex composed of C. parapsilosis, Candida orthopsilosis, Candida metapsilosis, and Lodderomyces elongisporus, and the Candida glabrata complex composed of C. glabrata, Candida nivariensis, and Candida bracarensis (1,(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17).Candida guilliermondii (the anamorph of Pichia guilliermondii), a species with decreased susceptibility to fluconazole and echinocandins, was reported as a common cause of candidiasis and sometimes even candidemia (18-21). Candida fermentati (the anamorph of Pichia caribbica), an emerging species that is very closely related to C. guilliermondii, has often been misidentified as C. guilliermondii using routine identification methods (22-26).…”