Summary: | Leukotoxic potential of <i>Aggregatibacter actinomycetemcomitans</i> strains has been studied by the use of several methods, and results differ depending on the methods used. The aim of the present study was to perform a comprehensive examination of the leukotoxic potential of a collection of <i>A. actinomycetemcomitans</i> strains by use of three quantitative methods, Western blotting, ELISA, and mRNA expression assay and compare these results with previous data obtained by a cell lysis assay. A higher leukotoxic potential among JP2 genotype strains compared to non-JP2 genotype strains of <i>A. actinomycetemcomitans</i> was found by Western blotting, ELISA and mRNA expression assay. Leukotoxicity as determined by cell lysis assay showed a variation among strains examined, not only depending on being part of JP2 genotype <i>vs</i>. non-JP2 genotype group of <i>A. actinomycetemcomitans</i>. The leukotoxicity of <i>A. actinomycetemcomitans</i> strains as determined by cell lysis assay did not correspond to the leukotoxic potential of <i>A. actinomycetemcomitans</i> strains as determined by three quantitative methods. A comparison of the results obtained by ELISA and mRNA expression assay showed a reasonable correlation between these two methods. It seems important to use more than one method to assess the LtxA-related virulence capacity of <i>A. actinomycetemcomitans</i> in order to obtain comprehensive understanding of the leukotoxic potential of <i>A. actinomycetemcomitans</i> strains.
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