Autochthonous and Dormant Cryptococcus gattii Infections in Europe

Ferry Hagen

, M. Francisca Colom, Daniëlle Swinne, Kathrin Tintelnot, Roberta Iatta, Maria Teresa Montagna, Josep M. Torres-Rodriguez, Massimo Cogliati, Aristea Velegraki, Arjan Burggraaf, Alwin Kamermans, Johanna M. Sweere, Jacques F. Meis, Corné H.W. Klaassen, and Teun Boekhout

Author affiliations: Royal Netherlands Academy of Arts and Sciences Fungal Biodiversity Centre, Utrecht, the Netherlands (F. Hagen, A. Burggraaf, A. Kamermans, J.M. Sweere, T. Boekhout); University Medical Center Utrecht, Utrecht (F. Hagen, T Boekhout); Universidad Miguel Hernàndez, Alicante, Spain (M.F. Colom); Institute of Public Health, Brussels, Belgium (D. Swinne); Robert Koch-Institut, Berlin, Germany (K. Tintelnot); Università degli Studi di Bari, Bari, Italy (R. Iatta, M.T. Montagna); Autonomous University of Barcelona, Barcelona, Spain (J.M. Torres-Rodriguez); Università degli Studi di Milano, Milan, Italy (M. Cogliati); University of Athens, Athens, Greece (A. Velegraki); University College Utrecht, Utrecht (J.M. Sweere); Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands (J.F. Meis); and Canisius Wilhelmina Hospital, Nijmegen (J.F. Meis, C.H.W. Klaassen)

Abstract

Until recently, Cryptococcus gattii infections occurred mainly in tropical and subtropical climate zones. However, during the past decade, C. gattii infections in humans and animals in Europe have increased. To determine whether the infections in Europe were acquired from an autochthonous source or associated with travel, we used multilocus sequence typing to compare 100 isolates from Europe (57 from 40 human patients, 22 from the environment, and 21 from animals) with 191 isolates from around the world. Of the 57 human patient isolates, 47 (83%) were obtained since 1995. Among the 40 patients, 24 (60%) probably acquired the C. gattii infection outside Europe; the remaining 16 (40%) probably acquired the infection within Europe. Human patient isolates from Mediterranean Europe clustered into a distinct genotype with animal and environmental isolates. These results indicate that reactivation of dormant C. gattii infections can occur many years after the infectious agent was acquired elsewhere.

During the past decade, the basidiomycetous yeast Cryptococcus gattii has stepped out of the shadows of its sibling C. neoformans. The latter species mainly infects immunocompromised persons, and C. gattii mainly infects apparently immunocompetent persons. C. neoformans is found globally, and C. gattii has been mostly limited to tropical and subtropical areas in Central Africa, northern Australia, and Central and South America (1). However, this distribution pattern changed after an unprecedented outbreak of C. gattii emerged in the temperate climate of British Columbia, Canada, and expanded to the Pacific Northwest region of Canada and the United States (1,2). Epidemiologic studies have shown that C. gattii occurs in areas other than tropical or subtropical zones, such as in Mediterranean Europe, northern Europe, and western Australia (3–5).
For the purpose of studying the epidemiology of C. gattii, a broad variety of molecular biological techniques have been developed, including PCR fingerprinting, restriction fragment length polymorphism analysis of the PLB1 and URA5 loci, amplified fragment length polymorphism (AFLP) fingerprint analysis, and several multilocus sequence typing (MLST) approaches (6–9). These laboratory investigations have shown that C. gattii can be divided into 5 distinct genotypes: AFLP4/VGI, AFLP5/VGIII, AFLP6/VGII, AFLP7/VGIV, and AFLP10/VGIV (8,9). Serotype B strains occur in genotypes AFLP4/VGI, AFLP6/VGII, and AFLP10/VGIV; serotype C strains are restricted to genotypes AFLP5/VGIII and AFLP7/VGIV (8).
Recently, a consensus MLST scheme was proposed for epidemiologic investigations of C. gattii and C. neoformans, specifically, the nuclear loci CAP59, GPD1, IGS1, LAC1, PLB1, SOD1, and URA5 (9). So far, this consensus MLST scheme has been used to study the population structure of C. neoformans strains from Thailand and C. gattii strains from Australia (3,10).
We investigated the occurrence of C. gattii in Europe, focusing on whether this pathogen is emerging and, if so, how to explain this emergence pattern. Furthermore, we explored whether the infections originated from Europe or were introduced from other continents. To achieve these goals, members of the European Confederation of Medical Mycology were asked to send recently obtained human patient isolates of the species for detailed AFLP and MLST analyses. Thus, the genetic diversity of the yeast was used to trace its geographic origin to identify where the infections were acquired. AFLP genotyping results were combined with published C. gattii MLST results from Byrnes et al. (11) and Fraser et al. (12), which were extended to match the Cryptococcus consensus MLST scheme (9). Our study produced the following 5 conclusions: all hitherto known genotypes of C. gattii are emerging in Europe; genotype AFLP4/VGI isolates predominate; a C. gattii cluster, which is endemic to Mediterranean Europe and genetically distinct from the other populations, exists; several human infections are caused by travel-related acquisition of C. gattii outside Europe; and autochthonous cases occur in Europe.