RESUMEN
Checkerboard DNA-DNA hybridisation enabled the quantitative analysis of plaque samples against 40 microbial species simultaneously, using digoxygenin-labelled, whole-genome DNA probes. This technique was initially developed to study the predominantly Gram-negative sub-gingival plaque microbiota. The aim of this study was to apply it to a suite of predominantly Gram-positive microorganisms, such as those implicated in cariogenesis. To specifically target Gram-positive species (and Candida albicans) required optimisation and modification of DNA extraction, prehybridisation, hybridisation, and antibody detection conditions. The suitability of the revised technique for clinical and epidemiological studies was confirmed using interproximal plaque from small groups of 5- to 6-year-old children of high (decayed, missing, or filled teeth (dmft)> or =5, n=8) and zero (n=5) caries rates.