Objective This retrospective surveillance study aimed to follow periodontitis‐associated bacterial profiles and to identify time‐dependent changes in antibiotic susceptibility patterns. Materials and Methods From 2008 to 2015, bacterial specimen from deep periodontal pockets were collected from a total of 7804 German adults diagnosed with periodontitis. Presence of selected bacteria was confirmed by anaerobic culture and nucleic acid amplification. Antimicrobial susceptibility of clinical isolates was tested by disc diffusion with antibiotics used for the treatment of periodontitis and oral infections. The prevalences of periodontal pathogens were calculated and temporal evolution of antimicrobial susceptibility towards amoxicillin, amoxicillin/clavulanic acid, metronidazole, doxycycline, clindamycin, azithromycin, ciprofloxacin and ampicillin was analysed with logistic regression. Results The prevalence of patients harbouring bacteria was 95.9% Fusobacterium nucleatum, 88.0% Tannerella forsythia, 76.4% Treponema denticola, 76.5%, Campylobacter rectus, 76.0% Eikenella corrodens, 75.0% Capnocytophaga spp., 68.2% Porphyromonas gingivalis, 57.7% Peptostreptococcus micros, 43.1% Prevotella intermedia, 30.4% Eubacterium nodatum and 21.5% Aggregatibacter actinomycetemcomitans. In 63.5% of patients, one or more isolates were not susceptible to at least one of the antibiotics tested. The data further revealed a trend towards decreasing susceptibility profiles (p < 0.05) with antibiotic non‐susceptibilities in 37% of patients in 2008 and in 70% in 2015. Conclusions The present study confirmed a high prevalence of periodontal pathogens in the subgingival microbiota of German periodontitis patients. The data revealed an incremental increase in isolates displaying resistance to some antibiotics but no relevant change in susceptibility to amoxicillin and metronidazole.

The periodontal microbiota is ecologically diverse and may facilitate colonization by bacteria of enteric origin (Enterobacteriaceae, Enterococci) and co-infections with Candida albicans, possibly producing subgingival biofilms with high antimicrobial tolerance. This retrospective surveillance study followed periodontitis-associated superinfection profiles in a large patient sample. From 2008 to 2015, biofilm samples from deep periodontal pockets were collected from a total of 16,612 German adults diagnosed with periodontitis. The presence of selected Enterobacteriaceae, Enterococci, and Candida albicans was confirmed in overnight cultures. Antimicrobial susceptibility of these clinical isolates was tested by disk diffusion with antibiotics routinely used for treatment of oral infections, e.g., amoxicillin (AML), amoxicillin/clavulanic acid (AMC), doxycycline (DO), and ciprofloxacin (CIP). The mean annual prevalence of patients harboring Enterobacteriaceae in periodontal plaques was 11.5% in total and ranged from 2.5% for Enterobacter cloacae to 3.6% for Klebsiella oxytoca, 1.1% for Klebsiella pneumoniae, 2.8% for Serratia marcescens, and 1.5% for Serratia liquefaciens. In comparison, the mean detection rates for microbiota typically found in the oral cavity were higher, e.g., 5.6% for Enterococcus spp. and 21.8% for Candida albicans. Among the Enterobacteriaceae, species harboring intrinsic resistance to AML (Enterobacter spp., Klebsiella spp., Serratia spp.) were predominant. Non-susceptibility to AMC was observed for Serratia spp. and Enterobacter cloacae. By contrast, Enterococcus spp. only showed non-susceptibility to DO and CIP. Trends for increasing resistance were found to AML in Serratia liquefaciens and to DO in Enterococcus spp. Trend analysis showed decreasing resistance to AMC in Serratia liquefaciens and Klebsiella oxytoca; and to DO in Serratia marcescens, liquefaciens, and Enterobacter cloacae. This study confirms the low but consistent presence of Enterobacteriaceae and Enterococci among the subgingival microbiota recovered from periodontitis specimen. Although their pathogenetic role in periodontal lesions remains unclear, their presence in the oral cavity should be recognized as a potential reservoir for development and spread of antibiotic resistance in light of antibiotic usage in oral infections.