Antimicrobial Susceptibility Of Subgingival Bacteria In The Patients With Chronic Periodontitis

Chronic periodontitis is one of the most popular types of periodontitis. The microorganisms and their metabolic products are the initiating factors of periodontitis. The subgingival plaque plays an important role in the chronic periodontitis.It has been proved that antimicrobial agents have positive clinical effect in adjunction to scaling and root planning in the treatment of severe periodontitis. Therefore to understand the antimicrobial susceptibility of subgingival plaque is vital to the treatment efficacy of antimicrobial agents.Objective To evaluate the in vitro antimicrobial susceptibility of subgingival microorganisms from the patients with chronic periodontitis.Methods The putative periodontal pathogens were isolated from subgingival plaque in the patients with chronic periodontitis. The antimicrobial susceptibility to 8 antimicrobial agents were studied and the minimum inhibitory concentrations were measured by the agar dilution technique.Results Twenty-three isolates from subgingival plaque samples from 32 patients were obtained. Most of the isolates were susceptible to amoxicillin. 87.5% of black pigmented Gram negative anaerobic bacilli were susceptible. No resistant strains to amoxicillin were detected. All the tested strains were susceptible to amoxicillin / clavulanic acid. No resistant strains to metronidazole, tinidazole and ornidazole were found. 93.8%, 81.3% and 75% of black pigmented Gram negative anaerobic bacilli were susceptible to these three agents. However, no good antimicrobial activity of azithromycin to the isolates in this study could be found. Only 50% strains of black pigmented Gram negative anaerobic bacilli were susceptible to it. The MIC of 3 strains was≥16μg/ml, and 1 strain of Prevotella >256μg/ml. 68.8% of black pigmented Gram negative anaerobic bacilli were susceptible to minocyclin whose MIC₅₀ was 0.25μg/ml and MIC₉₀ was 64μg/ml. 18.8% of the tested strains were resistant to clindamycin. 81.2% of the strains were susceptible to it.Conclusion An excellent antimicrobial activity of amoxicillin, amoxicillin/clavulanic acid, metronidazole, tinidazole and ornidazole to the the isolated periodontal pathogens in patients with chronic periodontitis could be found in this study. No resistant strains to them were detected. Good antimicrobial activities of clindamycin and minocyclin to the isolates were found. Several resistant strains were detected .The antimicrobial activity of azithromycin was not satisfying in this study.