Isolation, identification and growth characteristics of Porphyromonas gingivalis clinical strains

Abstract

Objective To isolate and identify Porphyromonas gingivalis(P.gingivalis) from clinical subjects,and analyse the growth characteristics of P.gingivalis. Methods Subgingival plaque samples were collected from patients with chronic periodontitis and periodontally healthy subjects,and anaerobic culture was performed.P.gingivalis strains were identified by PCR and 16S rDNA sequencing,and detection rate was analysed.Bacteria colonies and growth characteristics of the clinical strains of P.gingivalis were observed,and the biological properties were analysed. Results Six P.gingivalis clinical strains named as L2,L3,L4,L5,L11 and L12 were isolated from 146 subgingival plaque samples collected from 35 subjects.The detection rate of P.gingivalis was 27.4% in subgingival plaque samples of periodontally healthy subjects,86.7% in periodontally healthy sites of patients with chronic periodontitis,95.6% in periodontal pockets with probing depth of 4-6 mm,and 96.0% in periodontal pockets with probing depth 6 mm.Strains L2,L5,L11 and L12 formed black colonies on BHI plates after culture for 1 week.Strains L3 and L4 formed grey colonies 1 week after culture for 1 week,and formed black colonies after culture for 10 d.Strains L2,L4,L5 and L12 grew to exponential phase 30 h after inoculation,whereas strains L3 and L11 grew to exponential phase 60 h after inoculation. ConclusionP.gingivalis is one of the dominant pathogenic bacteria in periodontal pockets of patients with chronic periodontitis.The detection rate of P.gingivalis in healthy sites of patients with chronic periodontitis is significantly higher than that of periodontally healthy subjects,and the detection rates of P.gingivalis are higher in deeper periodontal pockets.The growth characteristics of P.gingivalis clinical strains vary from each other,indicating that the biological and pathogenic properties of P.gingivalis may be strain-specific.