Africa, Charlene Wilma Joyce; (1992) Techniques for the identification of oral treponemes. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The association of spirochaetes with chronic inflammatory periodontal disease (CIPD) is widely documented but based mainly on direct microscopic counts on the basis of their distinctive morphology. It has not yet been established whether any of the morphotypes observed in plaque are aetiological agents or merely opportunists which colonize as a result of the disease process. However, their consistent association with disease and their reduction after treatment as well as their possession of possible virulence mechanisms suggest a role for these organisms in the aetiology of CIPD. A major obstacle in the study of oral spirochaetes has been the inability to culture many of the morphotypes which have been microscopically observed. This has led to the search for alternative methods of identification and detection. The objectives of this study were therefore to evaluate and compare different methods for detecting T. denticola, a principal CIPD-associated spirochaete, in pure and mixed cultures and then to apply these methods to clinical plaque samples. The results indicated that ultrastructural studies could not reliably contribute to species differentiation although classification into morphotypes was achieved by measurement on an image analyser. Ultrastructural studies also permitted the description of spherical forms believed to be degenerative forms of T. denticola. Many of the differences previously suggested as indicative of species differentiation, were found to be artefacts due to inappropriate fixation. Serological detection methods demonstrated great diversity even though the same antibodies were used, while DNA probes detected T. denticola with similar frequency by two different hybridization methods. Comparison of the different detection as methods using each first as a test, then as a reference standard, led to the conclusion that no one method could be proposed as the most reliable for detecting T. denticola. However, in situ DNA hybridization appeared promising and potential to become a useful diagnostic aid in CIPD.

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