The Invader PLUS technology is a sensitive, rapid method for the detection and quantification of nucleic acid. While the original technology is based on the amplification by polymerase chain reaction (PCR) of the target sequence followed by its detection using the Invader technology, the current modification allows simultaneous PCR amplification and Invader reaction. The PCR primers and the Invader probes are designed to operate at the same temperature. This allows simpler design and faster results. This technology has been applied for the quantification of six periodontitis-related bacteria (Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Toreponema denticola, Tannerella forsythensis and Fusobacterium nucleatum). Direct comparison of this modified Invader PLUS with real-time PCR demonstrated similar linear range. Furthermore, testing of 64 volunteers showed a good correlation between both technologies with correlation factors r2 spanning between 0.827 and 0.987. We demonstrated here that the proposed improvement of the Invader PLUS allows the detection and quantification of DNA sequences using a simple design and protocol that can be implemented in clinical testing.

SUMMARY: When quantifying periodontopathic bacteria, it is important to use a convenient method that does not produce false negative results. The Invader assay is a convenient method because it does not involve gene amplification. The purpose of this study was to evaluate the validity of the Invader assay to quantify periodontopathic bacteria. The Invader technology was applied in quantifying five periodontopathic bacteria (Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, Prevotella intermedia, and Treponema denticola). The Invader assay produced a linear quantitative detection range over concentrations spanning seven exponential values, with a detection limit of 10 3.7 copies/tube and intra-day and inter-day variance of 0.1z to 4.7z and 0.1z to 3.4z, respectively, in quantifying five periodontopathic bacteria. We compared the results of the Invader assay with those of real-time polymerase chain reaction (PCR) performed for quantifying five periodontopathic bacteria in 22 patients with periodontitis. Among the Invader-detectable bacterial strains of each species, significant correlations were observed in the counts of concerned bacterial species between these two methods, with correlation coefficients ranging from 0.757 to 0.996. This study validated repeatability and reproducibility of the Invader assay in quantifying periodontopathic bacteria and demonstrated consistent agreement between the Invader assay and real-time PCR in quantifying periodontopathic bacteria.

Gut portions of soil-feeding termites belonging to the subfamily Termitinae generally show extensive alkalinity. An alkaliphilic and xylanolytic bacterium, strain SM-XY60, was isolated from the gut of such a soil-feeding termite Sinocapritermes mushae. This bacterium was a strictly aerobic endospore-forming rod, capable of growth at pH 6.5 to 10.5, and showing optimal growth at pH 9. The strain grew well on an alkaline medium containing K 2 CO 3 , but not Na 2 CO 3 . 16S rDNA analysis and physiological characterization revealed this strain to be a member of the genus Paenibacillus but distinct from any known species. The xylanase produced by the alkaline growing cells showed substantial activity and stability at high pH, implying an adaptation of the enzyme to the gut alkaline environment. The isolation of this alkaliphile suggests that the insect gut is of ecological significance for alkaliphiles.