title: Low antibiotic resistance among anaerobic Gram-negative bacteria in periodontitis 5 years following metronidazole therapy.
abstract: The objective of this study was to assess antibiotic susceptibility among predominant Gram-negative anaerobic bacteria isolated from periodontitis patients who 5 years prior had been subject to mechanical therapy with or without adjunctive metronidazole. One pooled sample was taken from the 5 deepest sites of each of 161 patients that completed the 5 year follow-up after therapy. The samples were analyzed by culture. A total number of 85 anaerobic strains were isolated from the predominant subgingival flora of 65/161 patient samples, identified, and tested for antibiotic susceptibility by MIC determination. E-tests against metronidazole, penicillin, amoxicillin, amoxicillin + clavulanic acid and clindamycin were employed. The 73/85 strains were Gram-negative rods (21 Porphyromonas spp., 22 Prevotella/Bacteroides spp., 23 Fusobacterium/Filifactor spp., 3 Campylobacter spp. and 4 Tannerella forsythia). These were all isolated from the treated patients irrespective of therapy procedures (+/-metronidazole) 5 years prior. Three strains (Bifidobacterium spp., Propionibacterium propionicum, Parvimonas micra) showed MIC values for metronidazole over the European Committee on Antimicrobial Susceptibility Testing break point of >4 μg/mL. All Porphyromonas and Tannerella strains were highly susceptible. Metronidazole resistant Gram-negative strains were not found, while a few showed resistance against beta-lactam antibiotics. In this population of 161 patients who had been subject to mechanical periodontal therapy with or without adjunct metronidazole 5 years prior, no cultivable antibiotic resistant anaerobes were found in the predominant subgingival microbiota.
authors.affiliation: Department of Oral Microbiology and Immunology, Institute of Odontology, Sahlgrenska Academy, University of Gothenburg, Sweden. Electronic address: dahlen@odontologi.gu.se.
authors.forename: G
authors.initials: G
authors.lastname: Dahlen
authors.affiliation: Department of Periodontology, Institute of Clinical Odontology, Faculty of Dentistry, University of Oslo, Norway.
authors.forename: H R
authors.initials: HR
authors.lastname: Preus
mesh_terms: D000658:Amoxicillin / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000890:Anti-Infective Agents / Q000627:therapeutic use*; D055113:Chronic Periodontitis / Q000188:drug therapy / Q000382:microbiology*; D002981:Clindamycin / Q000494:pharmacology; D024881:Drug Resistance, Bacterial / Q000187:drug effects*; D005500:Follow-Up Studies; D005881:Gingiva / Q000382:microbiology; D006089:Gram-Negative Anaerobic Bacteria / Q000187:drug effects*; D006801:Humans; D008795:Metronidazole / Q000627:therapeutic use*; D008826:Microbial Sensitivity Tests; D064307:Microbiota; D009664:Norway; D010406:Penicillins / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D010406:Penicillins; D008795:Metronidazole; D002981:Clindamycin; D000658:Amoxicillin
keywords: Antibiotics; Gram-negative anaerobes; Metronidazole; Periodontitis; Resistance; Subgingival microbiota