Methods: The study group was formed of 8 patients undergoing dental extractions under general anaesthesia. Peripheral venous blood samples were collected at baseline, 30 seconds and 15 minutes after the dental extractions. Blood samples were analysed for bacteraemia applying conventional microbiological cultures under aerobic and anaerobic conditions and pyrosequencing using universal bacterial primers that target the 16S ribosomal DNA gene.
Results: By applying conventional culture-dependent techniques and 16S rDNA pyrosequencing, the prevalences of bacteremia were respectively: 13% and 0% at baseline, 100% and 63% at 30 seconds and 75% and 0% at 15 minutes after finishing the surgical manipulation. By applying conventional microbiological methods, a single microbial species was detected in 75% patients; Streptococcus viridans was the most frequently cultured bacterium. By using pyrosequencing approaches however, the estimated blood microbial diversity after dental extractions was 13.40±1.7 bacterial families and 22.8±1.1 genera per sample.
Conclusions: The application of 16S rDNA pyrosequencing underestimated the prevalence and duration of bacteraemia following dental extractions, presumably due to not reaching the minimum DNA required for PCR amplification. However, this molecular technique, unlike conventional culture-dependent methods, revealed an extraordinarily high bacterial diversity of post-extraction bacteraemia. We propose that microorganisms recovered by culture are only the tip of an iceberg of a really diverse microbiota whose viability and potential pathogenicity should be further studied.