Multilocus sequence typing of Candida albicans isolates from the oral cavities of patients undergoing haemodialysis

Abstract

This study evaluates the prevalence, diversity, and genetic profiles of Candida albicans isolates recovered from the oral cavities of haemodialysis patients. Oral swab samples were obtained from haemodialysis patients (n = 126) and healthy control subjects (n = 233) and Candida species were characterised. There was no significant difference between the haemodialysis and control groups in the prevalence of yeast carriers (23.6% vs. 31.0%, respectively) or C. albicans carriers (19.8% vs. 21.0%, respectively). C. albicans was the most populous species in both cohorts, followed by C. parapsilosis. C. parapsilosis and C. glabrata were more prevalent in the haemodialysis group than in the control group (C. parapsilosis 5.6% vs. 0.9% and C. glabrata 3.2% vs. 0.4%, respectively; P < 0.05). C. albicans isolates were analysed by multilocus sequence typing and the results were used to construct a phylogenetic tree. Most haemodialysis isolates were placed into Clade 4 (20.0%) and Clade 19 (16.0%) and most control isolates into Clade 8 (17%) and Clade 4 (14.9%). Differences in the strain abundance in each clade were not statistically significant between the two groups. Moreover, there was no significant association between the health status or diagnosis and either the sequence types or clades.

Figure 1

Composition of yeast species in the oral cavities of haemodialysis patients and control subjects. C. albicans and C. parapsilosis were the two most common yeast species in both groups. Yeast carriers in the haemodialysis and control groups differed significantly in the percentage carrying C. albicans (64.1% vs. 89.1%, χ² = 8.507, P = 0.004) and C. parapsilosis (17.9% vs. 3.6%, χ² = 5.399, P = 0.020). Five subjects were colonised by C. albicans in combination with other species: C. glabrata or C. inconspicua by two subjects in the haemodialysis group, and C. parapsilosis, C. tropicalis, or Clavispora lusitaniae by three subjects in the control group.

Figure 2

Radial distribution of C. albicans isolates from the haemodialysis and control groups and reference strains. Allelic concatenated nucleic acid sequences from 25 haemodialysis patient isolates, 47 control subject isolates, and 3256 reference strains retrieved from an MLST database were phylogenetically analysed by UPGMA. Clade numbers were assigned according to reference. Three clades (10, 13, and 14) were not represented in isolates from either group. Open and closed circles represent control and haemodialysis isolates, respectively. Scale bar indicates p-distance.

Figure 3

Number of C. albicans isolates in each clade isolated from the haemodialysis patients and control subjects. Red and blue bars indicate haemodialysis and control groups, respectively. There were no significant differences in clade abundance between the two groups.