Al-Karaawi, Z.; (2005) Characterization of Candida species of the mouth in healthy patients and following bone marrow transplantations. Doctoral thesis , University of London.

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Abstract

This research work has investigated the molecular characterization of oral Candida of individuals (with no signs of candidosis) from different dental clinical settings in the United Kingdom and patients from diverse geographical regions of the world (UK, Greece, Italy and Brazil) who have undergone bone marrow transplantation (BMT). Subjects from the different dental settings were classified into healthy (subjects from a Private Dental Clinic, Prosthodontic Clinic and Orthodontic Clinic) or diseased subjects (patients from The Oral Medicine Clinic with mucosal diseases and Special Needs Clinic). The oral carriage of Candida and the presence of C. dubliniensis from the diseased subjects were significantly greater than that of the healthy subjects (p = 0.025 and p = 0.008 respectively). The healthy subjects had more non-albicans Candida (other than C. dubliniensis) than the diseased subjects (p = 0.024). Recipients of bone marrow transplantation (UK) had more non-albicans Candida (p = 0.024) than the healthy subjects. There was no difference in Candida diversity between isolates from BMT recipients from diverse geographic locales, although genotypic diversity among BMT recipients was observed from the Italian isolates (p = 0.041). PCR finger-printing with subsequent phylogenetic analysis revealed that there were significant differences between C. albicans strains from the UK BMT recipients with time and the strains from the UK BMT recipients were significantly more diverse than strains from the control subjects and the recipients of BMT from other geographical locales (p = 0.0001). Virulence attributes of Candida species were studied in-vitro utilizing adherence and proteinase assays. Candida isolates from BMT recipients in the UK had a trend of less in-vitro adherence (p = 0.076) than those from the healthy subjects, but there was no difference in adhesion between isolates from BMT recipients from different geographic regions. There was no difference in proteolytic activity of isolates from BMT recipients and control subjects, but there were significant differences in proteolytic activity between isolates from BMT recipients from different geographic regions (p = 0.001). Candida species from the Brazilian BMT recipients had very low extracellular proteinase activity. In-vitro fluconazole susceptibility test utilizing the National Committee for Clinical Laboratory Standards (NCCLS) M27-A showed that the isolates from BMT recipients from the UK were significantly more resistance to fluconazole than those from the control subjects (p = 0.027) or isolates from BMT recipients from other geographical regions (p = 0.009). There were no associations of Candida carriage, isolation of more non-albicans Candida, virulence attributes and developing of fluconazole resistance from subsequent sampling from the UK and Greek BMT recipients. Finally, the expression of secreted aspartyl proteinase (SAP) genes and agglutinin-like sequence (ALS) genes by strains of C. albicans utilizing RT-PCR was found to be influenced by the growth medium. It is concluded that bone marrow transplantation can have a significant impact upon the carriage of non-albicans Candida, virulence attributes and in-vitro fluconazole resistance of the oral Candida..

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