Genotyping Candida albicans from Candida leukoplakia and non-Candida leukoplakia shows no enrichment of multilocus sequence typing clades but enrichment of ABC genotype C in Candida leukoplakia

Abstract

Oral leukoplakias are histopathologically-diagnosed as Candida leukoplakia or non-Candida leukoplakia by the presence or absence of hyphae in the superficial epithelium. Candida leukoplakia lesions have significantly increased malignant potential. Candida albicans is the most prevalent fungal species associated with oral leukoplakia and may contribute to malignant transformation of Candida leukoplakia. To date, no detailed population analysis of C. albicans isolates from oral leukoplakia patients has been undertaken. This study investigated whether specific C. albicans genotypes were associated with Candida leukoplakia and non-Candida leukoplakia in a cohort of Irish patients. Patients with histopathologically-defined Candida leukoplakia (n = 31) or non-Candida leukoplakia (n = 47) were screened for Candida species by culture of oral rinse and lesional swab samples. Selected C. albicans isolates from Candida leukoplakia patients (n = 25), non-Candida leukoplakia patients (n = 19) and oral carriage isolates from age and sex matched healthy subjects without leukoplakia (n = 34) were subjected to multilocus sequence typing (MLST) and ABC genotyping. MLST revealed that the clade distribution of C. albicans from both Candida leukoplakia and non-Candida leukoplakia lesions overlapped with the corresponding clade distributions of oral carriage isolates and global reference isolates from the MLST database indicating no enrichment of leukoplakia-associated clones. Oral leukoplakia isolates were significantly enriched with ABC genotype C (12/44, 27.3%), particularly Candida leukoplakia isolates (9/25, 36%), relative to oral carriage isolates (3/34, 8.8%). Genotype C oral leukoplakia isolates were distributed in MLST clades 1,3,4,5,8,9 and 15, whereas genotype C oral carriage isolates were distributed in MLST clades 4 and 11.

Figure 1. UPGMA dendrogram depicting the genetic relatedness of all C. albicans isolates subjected to MLST and ABC genotyping analysis in the present study.

Individual isolates recovered from CL (n = 25) and NCL (n = 19) patients are indicated with the letters CL and OL in the isolate names, respectively. The numeral part of the isolate name refers to the corresponding patient numbers as shown in Table 1, column 1. Isolates recovered from age and sex-matched healthy control patients (n = 34) by oral rinse are indicated using the letters OC in the isolate name. Hyphenated letters A, B or C following each isolate name indicate ABC genotypes. The scale bar indicates p- distance. Distinct MLST clades are indicated by separated square parenthesis to the right of the isolate names and labelled with previously designated clade numbers . Numbers at clade branches indicate bootstrap support levels, based on 1000 replications. Overall, the population analysis based on MLST suggests no clonal enrichment of C. albicans isolates recovered from CL or NCL lesions. Isolates recovered from CL patients are distributed among eight clades, isolates from NCL patients are distributed among eight clades and isolates from healthy carriers are distributed among nine clades, with clade 1 predominating in all three groups.