Environmental sampling of Ceratonia siliqua (carob) trees in Spain reveals the presence of the rare Cryptococcus gattii genotype AFLP7/VGIV

Abstract

Background: Cryptococcus gattii is a pathogenic basidiomycetous yeast that is emerging in temperate climate zones worldwide. C. gattii has repetitively been isolated from numerous tree species. Ongoing environmental sampling and molecular characterization is essential to understand the presence of this primary pathogenic microorganism in the Mediterranean environment.

Aims: To report the first isolation of the rare C. gattii genotype AFLP7/VGIV from the environment in Europe.

Methods: Samples were collected from woody debris of carob trees (Ceratonia siliqua) and olive trees (Olea europaea) in El Perelló, Tarragona, Spain. Cryptococcus species were further characterized by using URA5-RFLP, MALDI-TOF, AFLP and MLST. The antifungal susceptibility profile to amphotericin B, 5-fluorocytosine, fluconazole, itraconazole, posaconazole and voriconazole was determined using Sensititre Yeast One and E-test.

Results: Cultures from one carob tree revealed the presence of ten Cryptococcus-like colonies. One colony was identified as C. gattii, and subsequent molecular characterization showed that it was an α mating-type that belonged to the rare genotype AFLP7/VGIV. Antifungal susceptibility testing showed values within the range of sensitivity described for other isolates of the same genotype and within the epidemiological cutoff values for this species.

Conclusions: The isolation of the rare C. gattii genotype AFLP7/VGIV in Spain is the first report in the European environment, implying the possible presence in other regions of the Mediterranean area, and underlines that clinicians must be aware for C. gattii infections in healthy individuals.

Keywords: Amplified fragment length polymorphism (AFLP); Antifungal susceptibility; Ceratonia siliqua; Cryptococcus gattii; Environmental sampling; Fingerprinting; Muestreo medioambiental; Multi-locus sequence typing (MLST); Polimorfismo de tamaño de fragmentos amplificados (AFLP); Sensibilidad antifúngica; Tipificación por secuenciación de múltiples loci (MLST).