A comparison between DNA-DNA checkerboard hybridization and culture techniques for the detection of Candida species in denture stomatitis

Introduction According to the literature, evidence on the potential use and application of DNA-DNA checkerboard hybridization technique in the diagnosis of Candida-associated Denture Stomatitis (DS) is scarce. Furthermore, the literature suggests that the inflammatory biomarkers in saliva could offer a new venue for the early diagnosis of this disease. Objectives The objectives of this master's research projects were to: 1) Provide evidence on the diagnostic accuracy of conventional culture and DNA-DNA checkerboard hybridization techniques for the detection of Candida species in DS, and to investigate its impact on the clinical diagnosis of this disease, and 2) To systematically examine the available evidence on the salivary biomarkers present in DS. Methods Objective 1): Palatal biofilm of 26 participants diagnosed with DS was analyzed to detect and quantify Candida species using culture and DNA-DNA checkerboard hybridization techniques. Using each technique as the standard reference for the other, the diagnostic accuracy of both techniques was examined, and compared using Kappa and McNemar tests. Spearman's rank test was used to examine the association between total Candida and total inflammation scores. Objective 2): The systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The level of evidence of the included studies was graded using the Oxford Center for Evidence-Based Medicine (OCEBM) 2011 scale. The methodological quality was assessed using Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement, and graded according to the Olmos scale. Results Objective 1): For all Candida species, the specificity of the culture technique ranged from 52% to 88.5%, and between 92.9% to 100% for the DNA-DNA checkerboard hybridization technique. There was a lack of agreement between the two techniques. The sensitivity for both the techniques was observed to be zero for all species. The correlation between Candida and inflammation scores was not statistically significant for the culture method, however a statistically significant and positive correlation was observed for the DNA-DNA checkerboard hybridization technique (p=0.05). Objective 2): The majority of studies included in the systematic review, showed that the levels of IL-6, CCL-3, TGF-β, GM-CSF, and TNF-α were higher in older individuals with DS, as compared to younger individuals with DS, or healthy individuals (p<0.05). In contrast, a few studies also observed a non-statistically significant difference in the levels of most salivary cytokines (IL-2, IL-12, IFN-Ƴ, IL-4, IL-8, IL-10, IL-17, TNF-α, and ICAM-1) between DS and healthy denture wearers. Conclusion The results of the studies undertaken during this master's research project suggest that DNA-DNA checkerboard hybridization shows greater diagnostic accuracy for the detection of Candida species in DS, as compared to the culture technique. Furthermore, the levels of some specific salivary cytokines may be associated with the palatal inflammation observed in DS. Further research is needed to confirm these results.

Keyphrases: Denture Stomatitis, DNA-DNA Checkerboard Hybridization, Candida, Oral Biofilm, Biomarkers, Systematic Review, Biofilm Oral