Up to date, Candida auris, a multidrug-resistant fungal pathogen, has not been isolated in Argentina, however, other emergent yeasts with reduced response to antifungal drugs are circulating in the country and cause severe fungal infection.

Objectives

To study and compare the in vitro antifungal susceptibility profile of emergent yeast species with those obtained from C. auris isolates.

Methods

We compared the antifungal susceptibility profile of C. auris (36) isolates obtained from patients living in Colombia, with the antifungal susceptibility profile of Candida haemulonii (21), C. haemulonii var. vulnera (10), C. duobushaemulonii (6), C. inconspicua (6), Debaryomyces nepalensis (6), Meyerozyma guilliermondii (67) and M. caribbica (8) isolates obtained from patients living in Argentina.

All isolates were identified by sequencing ITSs regions and D1/D2 domain of 26S of ribosomal DNA, and when necessary, by sequencing ACT1 gene.

The minimal inhibitory concentration (MIC) of amphotericin B (AB), fluconazole (FZ), itraconazole (IZ), voriconazole (VZ), anidulafungin (ANI), caspofungin (CAS) and micafungin (MICA) was determined according to EDef 7.3.2. from the EUCAST. MIC90, mode, and geometric mean were calculated.

For these emergent yeast species, clinical breakpoints have not been defined, thus, interpretative categories such as susceptible/resistant could not be used.

The results are summarized in the table.

For all the species tested, the azole drugs were not efficient enough to inhibit their growth.

Regarding amphotericin B, C. inconspicua, D. nepalensis, M. guilliermondii, and M. caribbica were inhibited at MIC90 0.5-1 mg/L, while for C. auris, C. haemulonii species complex the range of MIC90 values was 2-16 mg/L.

C. haemulonii species complex showed similar high MIC values for the antifungal drug assayed, confirming their characteristic of multidrug-resistant fungal pathogens. C. duobushaemulonii also showed higher MIC values (2 to 4-fold dilution) than those obtained with C. auris.

Conclusions

Although C. auris has not been isolated in Argentina yet, other yeast species with reduced antifungal susceptibility are circulating in the region and cause severe pathologies in the hosts.

The results here presented reinforce the need for continuous surveillance, not only to know the emergent species but also their antifungal susceptibility profile.