Aim The oral cavity represents a reservoir for antimicrobial resistance, and supragingival biofilms contribute to reduced antibiotic susceptibility. This study aimed to compare the antimicrobial susceptibility and biofilm-forming capacity of bacterial isolates obtained from dentally healthy individuals and participants with active carious lesions. Methods A total of 319 bacterial isolates from 40 participants were tested for susceptibility to clinically relevant antibiotics using disk diffusion and Etest methods, supplemented by β -lactamase testing. Biofilm formation was quantified by crystal violet staining and categorized into three levels based on optical density. Statistical analyses accounted for clustering of isolates within individuals. Results Resistant isolates were detected across all examined taxa. Significant group differences were observed for Veillonella parvula and Lachnoanaerobaculum saburreum . V. parvula isolates from caries participants showed higher proportions of intermediate or resistant classifications to ampicillin and a different distribution of biofilm categories compared to isolates from healthy individuals. For L. saburreum , resistant isolates from the healthy group were more frequently associated with stronger biofilm formation. Across species, stronger biofilm formation was generally associated with higher resistance among obligate anaerobes. Conclusion Specific bacterial taxa showed distinct differences in antibiotic susceptibility and biofilm-forming capacity between caries and healthy participants. The findings indicate that supragingival biofilms from caries-active individuals may harbour altered resistance patterns, particularly among obligate anaerobic species. These isolate-level observations underscore the need to further investigate how caries-associated ecological shift in oral biofilms relate to antimicrobial resistance.
Auer et al. (Fri,) studied this question.