Oral spirochetes, contribution to oral malodor and formation of spherical bodies

by De Ciccio, Angela

Spirochetes are putative periodontal pathogens because they are found in increased nurnbers in penodontitis. With severity of periodontal disease. there also appears to be an increase in oral malodor. This is due to a greater breakdown of tissues containing sulfùrated arnino acids such as cysteine, cystine, and methionine. Bactena in the oral cavity can metabolize these amino acids to produce volatile sulfur compounds such as hydrogen sulfide and methyl mercaptan that contribute to oral malodor. Detection of volatile sulfur compounds is usually perfonned by gas chromatography ar a portable sulfur rnonitor. but none of these methods provides direct evidence for the production of hydrogen sulfide fiom oral spirochetes. A successful method has been developed. as described in this thesis, to demonstrate that oral spirochetes are major contributors to oral malodor associated with periodontitis. This has been accomplished by modification of an established method for isolating these bacteria directly from subgingival plaques. A morphological variation of spirochetes, called a spherical body. exists. It has been postulated that this may be a donnant fonn of spirochetes used as a survival strategy. A number of environmental conditions were tested to determine whether or not they could contribute to spherical body formation in the oral spirochete Treponema denticoh ATCC 35405. Cells grown in the absence of rabbit serurn, volatile fatty acids, thiamine pyrophosphate, or yeast extract showed a dramatic increase in the numbers of spherical bodies. i? denticoh cells grown in the presence of the metabolic end-product lactic acid or at pH 7.42 instead of 6.8 also contained more spherical bodies than the contro 1. Les spirochètes sont associés à la périodontite parce qu'ils sont retrouvés plus fréquemment durant cette maladie. Proportionnellementà la sévérité de la périodontite, il y a habituellement une augmentation de l'odeur buccale. Ceci est causé par une augmentation de la désintegration des tissus contenant des acides aminés soufrés comme la cystéine. la cystine, et la méthionine. Les bactéries de la cavité buccale peuvent métaboliser ces acides aminés pour produire des composés de soufre volatils conune l'acide sulfhydrique et le mercaptan de méthyle. Habituellement, ces composés sont détectés par chromatographie en phase gaseuse ou a l'aide d'un moniteur portatif détectant le soufre, mais ces méthodes ne donnent aucune preuve de la production d'acide sulfhydrique par les spirochètes oraux. Une méthode est décrite dans cette thèse demontrant que les spirochètes oraux contribuent à I'odeur orale associée avec la périodontite. Ceci a été accompli par modification d'une méthode établie pour l'isolation de ces bactéries directement de la plaque subgingivale. II existe une variation morphologique des spirochètes. Ce sont des corps sphériques pouvant être une forme latente du spirochète, utilisée comme stratégie de survie. Différentes conditions environmentales ont été testées pour voir leurs effets sur la formation des corps sphériques dans le spirochète oral Treponemn denticoh ATCC 35405. Les cellules ayant poussé dans un milieu dépourvu de sérum de lapin, d'acides gras volatils, de thiamine pyrophosphate, ou d'extrait de levure ont demontré une augmentation du nombre de corps sphériques. Les cellules de T. denficola qui ont poussé dans un milieu contenant de l'acide lactique ou à pH 7.42 au lieu de 6.8 ont aussi formé plus de corps sphériques comparativementau contrôle. 1 would like to thank Dr. E.C.S. Chan for his guidance and patience, and most importantly, for giving me the oppodty to pursue graduate studies in the Faculty of Dentistry. 1 would also like to thank the other members of my laboratory: Richard McLaughlin, Antonia Klitorinos, and David Scott. Not only were they there for me when 1 needed help, but they also made my days of work more enjoyable. 1 am grateful to my parents for their encouragement, love, and support throughout my.lifetime. 1 thank them, too, for the sacrifices they made and for instilling in me a strong sense of moral values. My sisters, Veronica and Victoria, are definitely the best sisters in the world and 1 feel fortunate for having them in my life. 1 am also grateful for al1 the fnends 1 have made in the Strathcona Anatomy and Dentistry and Lyman Duff Buildings. Of particular importance is Celestino Di Flumen, my mentor, confidante, and fiend. He is always available to help me and he has allowed me to appreciate the aspects of life that are truly important. He also is capable of challenging me when 1 need a challenge. In addition, 1 would like to thank Marie-Claude Ouimet for her assistance in the translation of my abstract into French. Lastly, 1 thank Domenic Chiazzese, my best fnend and sou1 mate. My life has been that much better because of him.