BACKGROUND/AIMS: Information on the impact of sample storage prior to analysis by DNA methods is limited. The aim of this study was to investigate the effect of subgingival sample storage on bacterial detection and enumeration.

MATERIAL AND METHODS: Subgingival plaque samples were studied by a) checkerboard DNA-DNA hybridization by immediate processing, b) storage at + 4 degrees C for 6 weeks, c) storage at - 20 degrees C for 6 months or d) storage at - 20 degrees C for 12 months.

RESULTS: No differences in total DNA were found between protocol 1 and 2, or between protocol 3 and 4. Protocol 1 yielded 2.4 times more total bacterial DNA than did protocol 3 (P < 0.001). Actinobacillus actinomycetemcomitans and Campylobacter gracilis were detected in 21.1% of the immediately processed samples but only in 6.6% of the samples after 12 months of storage. Similar changes were noticed for Treponema denticola, which was detected in 22.3% and 9.2%, respectively. Streptococci spp., Fusobacterium nucleatum and Tannerella forsythia did not seem to be affected by storage. In contrast, the level of Campylobacter rectus detection frequency changed from 2.6% if processed immediately to 15.8% if samples were stored for 12 months.

CONCLUSIONS: In longitudinal clinical studies including microbiological samples and processed with DNA-DNA hybridization methods, samples should be stored for the same period of time before processing to avoid loss of microbiological information.

INTRODUCTION: Periodontitis is a common infectious disease to which Porphyromonas gingivalis has been closely linked, in which the attachment tissues of the teeth and their alveolar bone housing are destroyed. We conducted a study to determine if immunization using a purified antigen could alter the onset and progression of the disease.

METHODS: Using the ligature-induced model of periodontitis in Macaca fascicularis, we immunized five animals with cysteine protease purified from P. gingivalis and used an additional five animals as controls. Alveolar bone loss was measured by digital subtraction radiography.

RESULTS: Immunization induced high titers of specific immunoglobuin G serum antibodies that were opsonic. Total bacterial load, levels of P. gingivalis in subgingival plaque and levels of prostaglandin E(2) in gingival crevicular fluid were significantly reduced. Onset and progression of alveolar bone loss was inhibited by approximately 50%. No manifestations of toxicity were observed.

CONCLUSIONS: Immunization using a purified protein antigen from P. gingivalis inhibits alveolar bone destruction in a ligature-induced periodontitis model in M. fascicularis.