Multilocus sequence typing of strains from the Cryptococcus gattii species complex from different continents
Virginie Bellet1, Frédéric Roger1, Donika Krasteva1
1UMI 233 IRD-UM INSERM U1175 TransVIHMI, Infections mycosiques et parasitaires liées au VIH, Laboratoire de Parasitologie et de Mycologie Médicale, UFR Pharmacie, Montpellier, France.
Background:
Cryptococcus neoformans and Cryptococcus gattii species complexes are pathogens causing cryptococcal meningitis, a fungal infection that leads to death unless treated. Worldwide, it is estimated to kill over 180,000 individuals annually.
Objectives:
We aim to investigate the molecular diversity of C. gattii isolates from strains isolated from 1995 to the present day from different continents.
Method:
In this study, we analysed the molecular diversity by MLST and antifungal susceptibility by using the broth microdilution method according to the CLSI M27-A4 protocol of a total of 26 strains from Cryptococcus gattii species complex from both clinical and environmental sources.
Results:
Genotyping showed that most of the strains (17/26; 65.4%) belonged to serotype B and were distributed between three genotypes: VGI (13/17; 76.5%), VGII (3/17; 17.6%) and VGVI (1/17; 5.9%). The serotype C strains (9/26; 34.6%) were distributed between the VGIII (1/9; 11.1%) and VGIV (8/9; 88.9%) genotypes. The 26 strains belonged to 17 different MLST subtypes, and we highlight four new MLST genotypes (ST553, 554, 555 and 556). The two environmental strains were identified as serotype B and genotype VGI, but were of ST 51 and 154. All isolates have wild-type MIC of fluconazole and flucytosine. Regarding amphotericin B, five VGI strains showed MICs to AMB equal to 1 µg/ml, and according to the ECV for these genotypes, they were considered non-wild-type strains.
Conclusions:
The current study reveals the genetic diversity and new sequence types among strains from the C. gattii complex species.
Insights
Cryptococcus gattii causes deadly meningitis. This study reveals significant genetic diversity and new sequence types among C. gattii strains, highlighting variations in antifungal resistance.
Area of Science:
- Medical Mycology
- Molecular Biology
- Infectious Diseases
Background:
- Cryptococcus neoformans and Cryptococcus gattii species complexes are major causes of cryptococcal meningitis.
- This fungal infection results in over 180,000 deaths annually worldwide.
- Effective treatment is crucial to combat this life-threatening condition.
Purpose of the Study:
- To investigate the molecular diversity of Cryptococcus gattii isolates.
- To analyze strains collected globally from 1995 to the present.
- To understand the genetic variations within C. gattii species complexes.
Main Methods:
- Multilocus Sequence Typing (MLST) was employed to assess molecular diversity.
- Antifungal susceptibility was determined using the broth microdilution method (CLSI M27-A4 protocol).
- A total of 26 clinical and environmental C. gattii strains were analyzed.
Main Results:
- Genotyping revealed serotype B strains (65.4%) predominantly in VGI, VGII, and VGVI genotypes.
- Serotype C strains (34.6%) were found in VGIII and VGIV genotypes.
- Seventeen MLST subtypes were identified, including four novel genotypes (ST553-556).
- Most isolates showed wild-type Minimum Inhibitory Concentrations (MICs) for fluconazole and flucytosine.
- Five VGI strains exhibited non-wild-type MICs for amphotericin B.
Conclusions:
- The study demonstrates considerable genetic diversity within the Cryptococcus gattii complex.
- New sequence types (STs) were identified, expanding the known genetic landscape of C. gattii.
- Understanding this diversity is crucial for tracking and managing cryptococcal meningitis outbreaks.
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