Different species of bacteria important in the composition of dental plaque were tested for production of extracellular autoinducer-like activities that stimulate the expression of the luminescence genes in Vibrio harveyi. Several strains of Prevotella intermedia, Fusobacterium nucleatum, and Porphyromonas gingivalis were found to produce such activities. Interestingly, these bacteria belong to the same phylogenetic group, and they are periodontal pathogens important in the development of periodontal disease. They specifically produce extracellular signaling molecule related autoinducer-2 from V. haveyi. Nevertheless, they seem to be unable to produce homologues of acyl-homoserine lactones. Furthermore, Escherichia coli DH5α can be complemented by the introduction of a P. gingivalis gene with high homology to the luxS gene, which has been called luxSP.g.

Actinobacillus actinomycetemcomitans is considered to be one of the major oral putative pathogens, especially in cases of juvenile periodontitis. This microorganism requires nutritionally complex media for growth, and therefore the media for its primary isolation usually include blood agar or serum in their base. In this study we present a new medium, Dentaid-1, which improves the detection of A. actinomycetemcomitans in periodontal samples. In its composition, blood and serum have been omitted, hence reducing its cost and making it a more restrictive medium against the growth of other microorganisms with high nutritional requirements. The growth yields of pure cultures of the bacteria on Dentaid-1 were comparable to those on nonselective blood agar. Moreover, clinical efficacy was evaluated in subgingival samples from 77 subjects with adult periodontitis. Dentaid-1 detected A. actinomycetemcomitans in 24 subjects, while a previously described tryptic soy-serumbacitracin-vancomycin agar detected the microorganism in only 19 subjects (79.1%). Dentaid-1 is a low-cost, noninhibitory formula for the improved diagnosis and monitoring of patients subgingivally infected by this important oral putative pathogen.In the last few years, substantial evidence has emerged that Actinobacillus actinomycetemcomitans may be, along with Porphyromonas gingivalis, a major oral putative pathogen, as judged by this organism's rare occurrence in periodontally healthy individuals (25). A. actinomycetemcomitans has been isolated from adult periodontitis lesions, but less frequently and in lower numbers than from lesions in juvenile periodontitis subjects (21, 26). Treatment failures have been associated with the failure to reduce the amount of the microorganism in treated sites (14,17). Furthermore, data on the transmission of A. actinomycetemcomitans from host to host (5, 6, 32) and new evidence of its role as an infectious agent involved in disease development at extraoral sites (35) are providing one of the strongest associations between this oral pathogen and periodontal and systemic diseases.Existing data on the presence of A. actinomycetemcomitans in clinical infections have been obtained by using both selective and nonselective media for their isolation. Since A. actinomycetemcomitans is found in small proportions and because its growth can be inhibited in vitro by common oral streptococcal species (23), selective culture media are useful tools in the detection and enumeration of this bacterium. Although new molecular techniques are extremely sensitive in the detection of target bacteria (32,33,34), culture techniques are still the methods of reference for studying viable cells and a prerequisite for determining the antimicrobial susceptibility of a given pathogen.Among the selective culture media described for the isolation and enumeration of A. actinomycetemcomitans (11,16,23), tryptic soy-serum-bacitracin-vancomycin (TSBV) medium (23) has been the most widely used in the analysis of any kind of oral samples (4, 19) in studies t...