Evaluation of Antibiotic Resistance Genes in Commensal Gut Flora Among Healthy Individuals: A Hidden Reservoir for Resistance Transmission

Background Antimicrobial resistance (AMR) poses a major global health challenge, undermining the effectiveness of existing antibiotics and complicating the management of infectious diseases. The human gut microbiome serves as an important reservoir of antibiotic resistance genes (ARGs), which can be transferred among bacterial populations, including those inhabiting healthy individuals. Understanding the diversity and distribution of these ARGs at the community level is essential to identifying the hidden reservoirs of resistance within apparently healthy populations. However, data on the prevalence and determinants of ARGs in the general population of India remain limited. Methods A community-based cross-sectional study was conducted among 150 healthy adults (aged 18-60 years) in a tertiary care center of Central India from January to September 2025. Stool samples were analyzed using culture and multiplex quantitative PCR for nine major ARGs (blaTEM, blaCTX-M, blaNDM, tetM, ermB, sul1, qnrS, vanA, and mcr-1) and mobile genetic elements (MGEs). Associations between ARG carriage and demographic and exposure factors were assessed using the chi-square, Kruskal-Wallis, and regression analyses. Results The most common ARGs were tetM (42.7%), blaTEM (38.7%), and sul1 (34%) genes. ARG richness was significantly associated with recent antibiotic use (χ² = 17.3, p < 0.001) and MGE detection (χ² = 12.5, p < 0.001). Probiotic use was independently protective against blaTEM carriage (adjusted odds ratio = 0.19, 95% CI = 0.05-0.69, p = 0.011), whereas MGE detection showed a positive trend (p = 0.060). Linear regression (R² = 0.283) indicated that younger age (p = 0.014) and "Other" sex (p < 0.001) were associated with a higher total ARG load. Conclusion Healthy individuals harbor diverse and transmissible ARGs in their gut microbiota. Antibiotic exposure and MGEs increase ARG diversity, whereas probiotics may reduce blaTEM carriage. These findings highlight the need for One Health surveillance and prudent antimicrobial stewardship to limit the spread of AMR at the community level.