Influence of sampling strategy on microbiologic results before and after periodontal treatment.
BACKGROUND
The aim of this study was to test whether different sampling strategies would influence the microbiologic outcomes by assessing the bacterial load and composition of the subgingival microbiota by means of anaerobic culturing before and after periodontal treatment.


METHODS
The first study (1 versus 4 [1vs4]) included 33 patients with generalized chronic periodontitis. Two sampling strategies were compared, sampling one site from the deepest pocket in the mouth (M1) versus a pooled sample of four sites from the deepest pockets in each quadrant (M4). The second study (2 versus 4 [2vs4]) included 20 patients with generalized chronic periodontitis. The strategy M4 was compared to a pooled sample of two non-adjacent sites in the same quadrant (M2). All samples were processed identically by means of anaerobic culturing. In both studies, a pretreatment sampling was taken. However, in the second study (2vs4), subgingival samples were also taken at 1, 3, and 6 months after periodontal therapy. Quantitative data were compared between strategies by means of t test and signed-rank test; qualitative data were compared by means of 2 x 2 contingency tables.


RESULTS
Pretreatment samples showed that total anaerobic counts were significantly higher for M4 compared to M1 (P <0.001) and M2 (P = 0.025). However, there were no significant differences in regard to percentage of microbiota and counts for each pathogen. Most of the qualitative differences between strategies were caused by false negatives in M1 and M2. Post-treatment samples showed a reduction in total counts and a limited impact in the frequency of detection of periodontal pathogens. M2 detected a significant decrease in the frequency of detection of Porphyromonas gingivalis, which was not confirmed by the M4 strategy.


CONCLUSIONS
The criteria of selection and the number of sites selected when sampling the subgingival biofilm in patients with generalized chronic periodontitis may influence the detection and quantitation of periodontal pathogens when evaluated by culture especially after treatment.
Casas
Agustín
A
Section of Graduate Periodontology, Faculty of Odontology, University Complutense, Madrid, Spain.
Herrera
David
D
Martín-Carnes
Javier
J
González
Itziar
I
O'Connor
Ana
A
Sanz
Mariano
M
D000328:Adult; D000368:Aged; D016976:Aggregatibacter actinomycetemcomitans / Q000302:isolation & purification*; D001421:Bacteria, Anaerobic / Q000302:isolation & purification; D018929:Cell Culture Techniques / Q000379:methods; D015169:Colony Count, Microbial; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010514:Periodontal Pocket / Q000382:microbiology / Q000628:therapy; D010518:Periodontitis / Q000382:microbiology* / Q000628:therapy; D016966:Porphyromonas gingivalis / Q000302:isolation & purification*; D015983:Selection Bias; D013234:Stem Cells