Antibiotic Resistance and Biofilm‐Forming Capacity of Oral Biofilm Bacteria in Patients With Periodontitis and Healthy Individuals

ABSTRACT This study aimed to analyse antimicrobial resistance (AMR) in bacterial isolates from subgingival biofilms of patients with periodontitis and supragingival biofilms of orally healthy individuals, and to explore the association between biofilm‐forming capacity and AMR. Three hundred and forty‐seven bacterial isolates from 44 patients were analysed. Bacterial isolates were obtained from subgingival/supragingival biofilm and identified using MALDI‐TOF mass spectrometry. Antibiotic susceptibility was evaluated by the Kirby‐Bauer test, the E‐test, and a β‐lactamase activity assay, and biofilm formation capacity was assessed using the gentian violet assay. The 44 participants (median age 28.0 [25.0; 55.0]) were stratified into untreated generalised stage III/IV periodontitis ( n = 21) and orally healthy ( n = 23) groups. Among 347 isolates, 74.4% formed biofilms. AMR was generally higher in isolates from orally healthy subjects (77.7% vs. 59.1% in periodontitis patients, p p = 0.026). Multivariate binary logistic mixed models linked biofilm formation to AMR (OR: 1.66 CI: [1.12, 2.49]; p = 0.045 for severe biofilm formers and OR: 1.93 CI: [1.31, 2.83]; p = 0.004 for moderate biofilm formers). Phenotypic antimicrobial resistance was thus commonly detected throughout the cohort and was at least as frequent in orally healthy participants as in patients with periodontitis. Because the orally healthy group was substantially younger, this contrast is confounded by age and smoking and cannot be interpreted as an independent effect of periodontal status. Furthermore, this study might indicate that biofilm‐forming isolates may exhibit increased antibiotic resistance.