Characterisation of Candida species : a case study in three teaching hospitals in Ghana.
Thesis DisciplineBiological Sciences
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
Candida species are ubiquitous, ranging from pure saprobes through endo-symbionts of animals, to pathogens in many animals including humans. Some of the pathogenic species are of medical importance, especially Candida albicans. However, the prevalence of other non-albicans Candida species as human pathogens has been increasing worldwide. The aim of this study was to use conventional phenotypic tests and molecular methods to isolate, identify and characterise 600 Candida isolates from three teaching hospitals in Ghana, namely Korle Bu, Komfo Anokye and Tamale from mid-January to April, 2012. The prevalence of these species in cases of genitourinary candidiasis and pelvic inflammatory disease was investigated. Preliminary identification and characterisation of Candida isolates using four conventional phenotypic tests showed that C. albicans was the most common species, which constituted 41% of the isolates whereas non-albicans Candida species constituted 59% of the total number of Candida isolates. In patients presenting with vulvovaginal candidiasis (VVC) for at least two or more times, chi-square analysis indicates that the frequency of Candida species isolated were not statistically different from patients presenting for the first time with VVC. Candida albicans was the most common species in vaginal swabs from patients presenting with vulvovaginal candidiasis (VVC) for the first time in each of the three locations, present in 53.4% of the total swabs. The other species that were present were C. glabrata (21.6%), C. parapsilosis (15.5%), C. tropicalis (4.7%) and C. krusei (4.7%). Similar Candida species distributions were found in swabs taken from patients presenting with suspected pelvic inflammatory disease (PID). Across the three locations, however, there was a significant difference in the frequency of C. albicans, which was present in 68 and 69.6% of patients from Komfo Anokye and Tamale, but only 26.7% of patients from Korle Bu. Urine samples were taken in two of the locations, Korle Bu and Tamale, from female patients presenting with candiduria. Statistical analysis indicated a significant difference in the frequency of Candida isolates in cases of candiduria between the two locations. In Korle Bu, C. glabrata was the most prominent species (37.8%) followed by C. albicans (22.4%), C. parapsilosis (21.7%), C. tropicalis (10.5%), C. krusei (7%) and C. lusitaniae (0.7%). In Tamale, the species distribution was C. albicans (60.9%), C. glabrata (21.7%), C. parapsilosis (13%) and C. krusei (4.3%). The data highlight the prevalence of species other than C. albicans in case of candidiasis in Ghana. Delineation of C. albicans strains using the 25S rDNA to investigate the genotypic variation among C. albicans isolates showed that genotype A constituted about 95% of the Ghanaian C. albicans isolates, genotypes B and C constituted 2.5% each respectively. The general-purpose genotype (GPG) which corresponds to clade 1 among C. albicans was also investigated to know the prevalence of clade 1 among the C. albicans isolates investigated. The presence or absence of general-purpose genotype (GPG) gene was used to categorise the 240 C. albicans to clade 1 or other clade. The test revealed that 64.2% had the GPG genotype which corresponds to clade 1 and the remaining 35.8% were of non-GPG genotype; thus belongs to other clades. The population structure of C. albicans from the three teaching hospitals indicates a mainly clonal and homogeneous population across the three sampling locations from Ghana. Molecular analyses of the transposable group 1 intron in the ITS1-5.8S-ITS2 region using universal primer pair ITS1 and ITS4 revealed the presence of two rare Candida species; Candida rugosa and Candida mesorugosa. To the best of my knowledge this is the first report of either of these in Africa. Antifungal susceptibility tests among Candida isolates recovered from patients presenting with clinically suspected or symptomatic candidal vaginitis for the first time and patients presenting with candidal vaginitis on two or more occasions revealed a high percentage of Fluconazole-resistant C. albicans. This study highlights the prevalence of species other than C. albicans in cases of candidiasis in Ghana. Furthermore, this study has also demonstrated that no single conventional phenotypic test has been highly efficient to delineate Candida species into their respective species type. Thus, development of an identification scheme, which can discriminate between Candida isolates both at species and strain levels, will have prognostic and therapeutic significance for effective patient management.