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The Interaction between Guava-extract and Aggregatibacter actinomycetemcomitans Leukotoxin
Umeå University, Faculty of Medicine, Department of Odontology.
Umeå University, Faculty of Medicine, Department of Odontology.
2014 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]


Previous studies have shown that the highly leukotoxic JP2 clone of Aggregatibacter actinomycetemcomitans (Aa) was strongly associated with the initiating of aggressive periodontitis amongst adolescents in Ghana. In this population, conventional periodontal treatment cannot be performed because of limited resources. The focus of the present study has been on developing a preventive tool for eliminating Aa leukotoxin (LtxA). Recent studies indicate that extract from Guava inhibits the activity of the Aa leukotoxicity. However, it requires more knowledge about Guava LtxA neutralizing properties in order to be used in future prevention strategies of aggressive periodontitis. Our aim has been to determine the persistence of the inhibitory effect of guava on leukotoxicity of Aa.


We examined the bindings of LtxA-neutralizing Guava components to different isolates of the Aa bacterium including the high leukotoxic JP2 clone. The experiments began by culturing the Aa bacteria as a biofilm on a plastic surface which then became exposed to guava extract for 30 min. The guava extract was then replaced with a plane culture medium for different times before we added cultured macrophages (THP-1 cells). The cytolysis effect of LtxA was quantified as the releases of cytosolic lactate dehydrogenase (LDH) or decrease in the neutral red uptake of Aa-exposed (2 hr) cultures of human macrophages (THP-1 cells). 


All experiments showed that leukotoxicity caused by the tested isolates of Aa became significantly reduced in the presence of guava-extract. The results also showed that the persistence of guava on leukotoxicity from Aa remained for 24 hr after removal of the unbound guava components. The persistence of the LtxA neutralizing effect for at least 24 h indicate a possibility in using guava components as a preventive tool for aggressive periodontitis associated with the presence of Aa.

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URN: urn:nbn:se:umu:diva-102414OAI: diva2:807735
Available from: 2015-04-24 Created: 2015-04-24 Last updated: 2015-04-24Bibliographically approved

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