Candida nivariensis - a new emergent agent of vulvovaginal candidosis
February 29 2016
Candida nivariensis has been recently described as a new emergent agent of VVC and other human infections. Its phenotypic characteristics are very similar to C. glabrata and can be easily misidentified as such. It frequently exhibits multi-azole resistance and has MICs similar to or even more elevated than those for C. glabrata.
Vulvovaginal candidosis (VVC), also known as vaginal thrush, is one of the most common forms of vaginitis affecting >75% of women at least once in their lifetime. Over 5% of women in childbearing age suffer from recurrent (≥4 episodes/year) VVC at some point of their life. VVC is most often caused by Candida albicans although non-albicans Candida species, especially C. glabrata but also C. parapsilosis, C. tropicalis and C. lusitaniae are other significant causes. Candida africana was originally described as a new C. albicans-like species causing amphotericin B-resistant VVC but more recent genome based studies have shown that it is only a variant of C. albicans rather than a genuine new species. Candida nivariensis has not previously been found to cause VVC. By micrsocopy it is not possible to distinguish C nivariensis
It is not possible to distinguish C. nivariensis by microscopy and the identification of C. nivariensis is challenging based on carbohydrate assimilation (API ID32C): only the fermentation of trehalose can distinguish it from C. glabrata. Also, C. glabrata grows as small, pink colonies on CHROMagar where as C. nivariensis often fails to do so. Very small white colonies on CHROMagar should trigger further identification tests. C. nivariensis can be identified by matrix-assisted laser desorption/ionization time of flight (MALDI-TOF). Using Bruker Microflex platform and MALDI Biotyper (Bruker Daltonik, Bremen, Germany) Aznar-Marin et al report scores ranging between 1.802 and 2.086 for C. nivariensis, indicating secure genus and probable species identification. The identification can also be confirmed by sequencing using ITS-1 and ITS-4 primers and a BLAST database search.
It is important to remember that asymptomatic vaginal colonisation with Candida is common, and symptoms only develop when the amount of Candida exceeds the tolerance of the underlying mucosa or skin. This can happen if the balance between the Candida and normal bacterial flora is altered, or the immunological status of the patient is impaired. However, the symptoms for VVC are non-specific and shared with many dermatological and allergic conditions whereby isolation of Candida in vaginal secretions is only part of the diagnosis. If VVC does not respond to appropriate antifungal treatment then an alternative diagnosis is more likely.