Candida albicans: genotyping methods and clade related phenotypic characteristics

Molecular typing and genetic relatedness of 72 clinical Candida albicans isolates from poultry

Candida albicans is the most prevalent opportunistic fungus of humans and animals. While most studies focus on human isolates, they rarely focus on poultry isolates. In this study, C. albicans strains were recovered from poultry in the southern Hebei Province (China) and identified. Molecular typing and analyses were performed to understand the molecular epidemiology and genetic relatedness of the strains. The fungi were isolated from live birds with presumed candidiasis or their corpses. The isolates were identified based on morphology, differential medium culture, and rDNA internal transcribed spacer sequencing. The identified C. albicans strains were analyzed by ABC genotyping and multilocus sequence typing. Clonal groups were identified using the eBURST (version 3.0) software, and an UPGMA phylogenetic tree was constructed using the MEGA (version 6.06) software. Overall, 72 isolates were divided into three genotypes (A, B, and C), 48 novel sequence types (STs), five groups with 10 singletons, and four clades. Results indicated that candidiasis is common in poultry in the southern Hebei Province, and that the genetic composition of the C. albicans poultry population from the area is relatively complicated. Based on the eBURST analysis for the STs in this study and others, we suggest that C. albicans poultry isolates were relatively independent but not completely separated from human isolates. The strains with the same or closely related genotypes but recovered from both birds and humans could have transferred and evolved between the two types of host.

Phenotypic diversity and correlation between white-opaque switching and the CAI microsatellite locus in Candida albicans

Candida albicans is a commensal fungal pathogen that is often found as part of the human microbial flora. The aim of the present study was to establish a relationship between diverse genotypes and phenotypes of clinical isolates of C. albicans. Totally 231 clinical isolates were collected and used for genotyping and phenotypic switching analysis. Based on the microsatellite locus (CAI) genotyping assay, 65 different genotypes were identified, and some dominant types were found in certain human niches. For example, the genotypes of 30-44 and 30-45 were enriched in vaginal infection samples. C. albicans has a number of morphological forms including the single-celled yeasts, multicellular filaments, white, and opaque cell types. The relationship between the CAI genotype and the ability to undergo phenotypic switching was examined in the clinical isolates. We found that the strains with longer CAA/G repeats in both alleles of the CAI locus were more opaque competent. We also discovered that some MTL heterozygous (a/alpha) isolates could undergo white-opaque switching when grown on regular culture medium (containing glucose as the sole carbon source). Our study establishes a link between phenotypic switching and genotypes of the CAI microsatellite locus in clinical isolates of C. albicans.

Importance of Diversity in the Oral Microbiota including Candida Species Revealed by High-Throughput Technologies

Taking advantage of high-throughput technologies, deep sequencing of the human microbiome has revealed commensal bacteria independent of the ability to culture them. The composition of the commensal microbiome is dependent on bacterial diversity and the state of the host regulated by the immune system. Candida species are well known as components of the commensal oral microbiota. Candida species frequently colonize and develop biofilms on medical devices like dentures and catheters. Therefore, Candida biofilm on dentures leads to a decrease in the bacterial diversity and then to a change in the composition of the oral microbiota. A disturbance in the balance between commensal bacteria and the host immune system results in a switch from a healthy state to a diseased state even in the limited oral niche.