A molecular ecological approach to the detection and designation of the etiological agents of a model polymicrobial disease.

The application of the original Koch postulates and the molecular Koch postulates in the definition of the etiological agents of polymicrobial diseases has received little or no attention. In the present study, denaturing gradient gel electrophoresis (DGGE) of oral samples (n = 3) from each of 3 categories of animals (healthy, diseased [gingivitis], and then oxytetracycline-treated) was used and revealed different bacterial community structures in a model polymicrobial disease (gingivitis) and after clinical cure. Potential microbes associated with the disease and belonging to the following families were identified: Fusobacteriaceae, Porphyromonadaceae, Flavobacteriaceae, Alcanivoracaceae, Bacteroidaceae, Xanthomonadaceae, and Neisseriaceae. Liquid chromatography-mass spectrophotometric analysis of culturable anaerobic bacteria culture supernatant revealed 3 major compounds (2-hydroxycaproic acid, phenyllactic acid, and indole acetic acid) that differentiated the healthy and disease groups. Results indicate that different microbial community structures were associated with the healthy and disease oral states. The results demonstrate the potential of DGGE as a tool in the detection and designation of etiological agents of polymicrobial diseases.