Patients with active dental caries may harbor supragingival bacteria with species-specific differences in antibiotic resistance and biofilm-forming capacity compared with those with good oral health.
In a study, researchers analyzed 319 bacterial isolates obtained from the supragingival plaque of 40 adult participants at three German universities, including 17 patients with at least two active dentinal caries and 23 healthy controls. They tested antimicrobial susceptibility using disk diffusion and Etest methods as well as quantified biofilm formation with crystal violet staining across 15 oral bacterial species representing facultative and obligate anaerobes.
The clearest differences were observed in Veillonella parvula, of which 21% of the isolates were susceptible to ampicillin among the patients with active dental caries compared with 73% of those among healthy patients. Intermediate susceptibility classifications occurred in 71% vs 23%, respectively. The researchers also found differences in biofilm formation for V. parvula. For instance, 79% of isolates from patients with caries were categorized as moderate biofilm producers, whereas 82% of isolates from healthy patients were classified as non–biofilm producers.
Differences also emerged in Lachnoanaerobaculum saburreum. In isolates from healthy patients, resistant bacteria were more frequently associated with stronger biofilm formation, including moderate and strong biofilm-producing categories. In contrast, isolates from patients with caries were predominantly non–biofilm producers.
Across obligate anaerobic species overall, greater biofilm formation was associated with higher proportions of antibiotic resistance. Moderate and strong biofilm-producing isolates demonstrated more antimicrobial resistant outcomes compared with non–biofilm producing isolates.
Resistant isolates were identified across all tested taxa, including Streptococcus oralis, Streptococcus mutans, Actinomyces oris, Neisseria species, Capnocytophaga ochracea, Eikenella corrodens, Prevotella nigrescens, Fusobacterium nucleatum, Parvimonas micra, L. saburreum, and V. parvula. Beta-lactamase activity was confirmed in eight bacterial isolates, most commonly in F. nucleatum.
The researchers cautioned that the findings should be interpreted as exploratory because of the study’s small sample size and uneven species representation across the groups. Multiple bacterial isolates could originate from the same patient, introducing potential intra-subject dependency. The culture-based design also limited analysis to cultivable bacteria and did not capture broader ecologic interactions within multispecies oral biofilms.
Overall, the findings did not support a universal increase in antimicrobial resistance among patients with caries.
“The observed associations were predominantly species-specific rather than universal, indicating that caries-related ecological changes do not uniformly translate into resistance or biofilm phenotypes across all taxa,” wrote lead study author David L. Auer, of the Department of Operative Dentistry and Periodontology at the Center for Dental Medicine in the Faculty of Medicine at the University of Freiburg in Germany, and colleagues.
The study was funded by the Ministry of Science, Research and the Arts of the State of Baden-Württemberg, and the Deutsche Forschungsgemeinschaft DFG. Co–study author Fabian Cieplik reported serving on the editorial board of Frontiers at the time of submission.
Source: Frontiers in Oral Health
