Phenotypic Biofilm-Forming Capacity and Antimicrobial Resistance Profiles of Culturable Subgingival Bacteria in Various Stages and Grades of Periodontitis in Iraqi Adults

Background: There is a lack of phenotype-based data associated with the 2017 stage–grade framework for periodontal disease in Iraq, and subgingival biofilms maintain the periodontal dysbiosis and may include clinically relevant antimicrobial non-susceptibility bacteria. Objective: To evaluate if the ability to form biofilm and antimicrobial resistance profiles of culturable subgingival bacterial isolates vary with periodontitis stage and grade and if there is an independent association between strong biofilm-forming ability and antimicrobial non-susceptibility. Design: This is a multicenter analytical cross-sectional study comprised of 200 adults with Stage I–IV periodontitis. Plaque from four subgingival deepest sites, which were not adjacent, was collected. Isolates were grown aerobically, capnophilically, and anaerobically and phenotype with automated and/or mass-spectrometric confirmation, when available. Biomass levels of biofilms were measured in 96 well plates by crystal violet and the OD-c cutoff method. Broth microdilution methods were used for aerobic/facultative isolates and agar dilution methods for anaerobes were used to determine minimum inhibitory concentrations. Population-averaged logistic models with patient clustering and clinical and demographic covariates. Results: 645 isolates were recovered. Biofilm formation was found to be strong in 45.9% of the isolates (296) and it increased with an increase in periodontitis stage and grade. The highest amount of biofilm biomass was found with Porphyromonas gingivalis, Fusobacterium nucleatum, Staphylococcus aureus, enterococci, and opportunistic Gram-negative isolates. Testing of the individual isolates of the biofilms showed a higher number of antimicrobial non-susceptible phenotypes on the tested panel and a higher number of multidrug-resistant phenotype/multiple-antimicrobial non-susceptibility phenotype in strong biofilms. Strong biofilm formation (aOR 2.10, 95% CI 1.04–4.25) was associated with stage III–IV disease after adjustment, and strong biofilm formation was an independent predictor of the composite resistance outcome (aOR 5.06, 95% CI 3.06–8.39). Conclusions: Stronger recovery of subgingival bacteria with higher ability to form biofilms, and less susceptible to the culture conditions, was correlated with advanced and rapidly progressed periodontitis. Species-resolved MIC surveillance could be useful in antimicrobial stewardship when there is a clinical need for adjunctive antibiotic use.