A Longitudinal Study of Antimicrobial Resistance in Oral Bacterial Isolates From Periodontitis Patients in Taiwan

INTRODUCTION AND AIMS: The oral cavity harbours a complex microbial ecosystem that plays a critical role in periodontal health and disease. Despite growing concerns over antimicrobial resistance (AMR), long-term surveillance of antibiotic susceptibility in oral bacteria remains limited. This study aimed to assess the temporal trends in AMR among oral bacteria isolated from periodontitis patients in Taiwan over a 14-year period, with emphasis on genus-specific, Gram-specific, and sex-related patterns. METHODS: A total of 980 bacterial isolates were obtained from 466 periodontitis patients between 2008 and 2021. E-strip testing was performed for six antibiotics: amoxicillin, ciprofloxacin, clindamycin, metronidazole, minocycline, and amoxicillin-clavulanic acid. Susceptibility data were analysed by year and bacterial genus. RESULTS: Polymicrobial infections were predominant (98.1%), and resistance rates increased significantly over time, particularly for metronidazole (from 37.8% to 90.9%) and ciprofloxacin (from 33.1% to 51.5%). Streptococcus, Peptostreptococcus, and Capnocytophaga were more prevalent in females, while Neisseria, Fusobacterium, and Pseudomonas were more common in males. High resistance rates were observed in Neisseria, Escherichia, and Staphylococcus, with over 80% of some isolates resistant to multiple agents. CONCLUSION: Our findings reveal a progressive rise in AMR among oral bacteria and highlight the need for localized antibiotic stewardship in dentistry. This is the first long-term oral AMR surveillance study in Taiwan and offers a foundation for updating empirical treatment guidelines and informing public health policy. CLINICAL RELEVANCE: This study provides long-term, real-world AMR data for oral bacteria in Taiwan. The findings support more informed antibiotic selection in periodontal therapy and highlight the need to re-evaluate empirical use of metronidazole and fluoroquinolones in routine dental practice.