Detection of clinically relevant resistance genes in subgingival biofilms of chronic periodontitis: A cross-sectional molecular surveillance study.

Background: Antimicrobial resistance (AMR) has emerged as a major barrier to effective periodontal therapy, particularly when adjunctive antibiotics are prescribed empirically. The oral cavity-especially the subgingival biofilm-serves as a dynamic reservoir for antibiotic resistance genes (ARGs), yet data from the Indian population remain limited. Aim: To detect and characterize the presence and co-occurrence of clinically relevant ARGs-tet(M), blaTEM, and erm(B)-within subgingival biofilms of Indian patients with chronic periodontitis through PCR-based molecular surveillance. Methods: This cross-sectional pilot study (n = 20) was conducted among systemically healthy adults diagnosed with chronic periodontitis (2018 AAP-EFP criteria). The sample size was pragmatically defined to assess feasibility and prevalence trends. Subgingival plaque from the deepest pocket per patient (non-pooled) was collected before instrumentation by a single calibrated examiner. DNA was extracted and subjected to end-point PCR targeting tet(M), blaTEM, and erm(B), with gene-specific positive and no-template negative controls included in each run. Amplification reproducibility was verified through cross-laboratory concordance testing. Descriptive and Fisher's exact analyses were applied to explore gender-wise patterns. Results: tet(M) was detected in 65 % of patients, blaTEM in 45 %, and erm(B) in 30 %. Dual-gene co-occurrence was observed in 35 %, while 20 % harbored all three genes. The most frequent association was tet(M) + blaTEM. Males exhibited a higher mean gene burden (1.8 ± 0.4) than females (1.4 ± 0.5), though differences were not statistically significant (p > 0.05). Conclusion: This pilot demonstrates a substantial prevalence and co-occurrence of resistance determinants in periodontal biofilms, underscoring the oral cavity's role in local and systemic AMR propagation. While preliminary, these findings support incorporating molecular resistance surveillance into periodontal diagnostics and tailoring region-specific antibiotic stewardship strategies to preserve therapeutic efficacy.