# Antimicrobial Susceptibility of Subgingival Bacteria in Canines With Periodontal Disease

## TL;DR

This study examines antibiotic resistance in bacteria from dogs with periodontal disease in Peru, showing many common antibiotics are ineffective.

## Contribution

The study provides the first regional evidence of antimicrobial resistance patterns in subgingival bacteria from dogs with periodontitis in South America.

## Key findings

- High resistance to metronidazole (87.9%) was observed among subgingival bacteria.
- Ciprofloxacin showed the lowest resistance (10.49%) compared to other tested antibiotics.
- Staphylococcus aureus and Porphyromonas gingivalis were the most frequently isolated species.

## Abstract

Periodontal disease is a highly prevalent condition in dogs; however, information on subgingival bacterial composition and antimicrobial susceptibility remains limited, particularly in South America. This study evaluated the antimicrobial susceptibility patterns of subgingival bacteria isolated from dogs with periodontitis. Samples were collected from 49 dogs with clinical signs of periodontal disease attending veterinary clinics in Piura, northern Peru. Aerobic, facultative anaerobic, and strict anaerobic bacteria were isolated and identified using culture‐based methods, and antimicrobial susceptibility was assessed by the Kirby–Bauer disk diffusion method against clindamycin, amoxicillin plus clavulanic acid, metronidazole, ciprofloxacin, doxycycline, and cephalexin. A total of 305 pure colonies were isolated, of which 55% corresponded to aerobic and facultative anaerobic bacteria and 45% to strict anaerobes. Eighteen genera of aerobic and facultative anaerobic bacteria and thirteen genera of strict anaerobes were identified, with Staphylococcus aureus and Porphyromonas gingivalis being the most frequently isolated species. High levels of antimicrobial resistance were observed, particularly to metronidazole (87.9%), while resistance to ciprofloxacin was low (10.49%). Resistance to clindamycin, amoxicillin plus clavulanic acid, doxycycline, and cephalexin ranged between 50% and 70%. These findings highlight the limited effectiveness of commonly prescribed antimicrobials for canine periodontal disease and underscore the risks associated with empirical antibiotic use in veterinary dentistry. The study provides the first regional evidence of antimicrobial resistance patterns in subgingival bacteria from dogs with periodontitis. The results support the need for culture‐guided therapy, antimicrobial susceptibility testing, and the implementation of antimicrobial stewardship strategies in routine veterinary dental practice.