Detection of Peptostreptococcus micros DNA in clinical samples by PCR

Peptostreptococcus micros is a gram-positive anaerobic coccus which, althou gh considered to be a natural commensal of the human oral cavity, is associ ated with periodontal, endodontal and peritonsillar infections. Identificat ion of the organism has to date relied upon conventional culture methods an d biochemical analyses. The purpose of this study was to develop a PCR meth od for rapid and specific identification of this organism in clinical sampl es. A pair of primers was selected, each of which was specific at the 3' en d for I? micros DNA; they were used in the PCR assay, resulting in a 1074-b p product. The primers were shown to be specific for P. micros DNA as no PC R products were obtained when genomic DNA extracts from a wide range of oth er Peptostreptococcus species and other oral bacteria were used as template s. The PCR assay was then applied to the identification of P. micros DNA in subgingival plaque samples from adult periodontitis patients and pus sampl es from subjects with acute dento-alveolar abscesses. Confirmation of speci fic amplification of P. micros DNA was obtained by digestion of PCR product s with the restriction endonuclease RsaI, which gives a unique restriction profile for 19 micros, and DNA sequencing. Sixty-eight subgingival plaque s amples from 18 patients were analysed, of which 19 (28%) were positive for P. micros DNA; the proportion of patients carrying P. micros DNA in at leas t one sampled site was 11 (61%) of 18, Twenty (71%) of 28 pus samples analy sed by PCR contained P. micros DNA, These results confirm that P. micros ma y be involved in the aetiology of acute dentoalveolar abscesses and adult p eriodontitis. The PCR assay provides a more rapid and reliable alternative to conventional methods for identification of P. micros in clinical samples .