Assessment of antimicrobial resistance patterns in bacterial isolates from canine urinary tract infections and evaluation of alternative therapeutic options.

Project Abstract

This study comprehensively investigates antimicrobial resistance (AMR) patterns in bacterial isolates from canine urinary tract infections (UTIs) and evaluates alternative therapeutic options to inform evidence-based clinical management. A cross-sectional collection of urine samples was obtained from companion dogs presenting with clinical signs of UTI across multiple veterinary clinics over a 12-month period. Bacterial isolates were identified to species level using standard microbiological techniques and MALDI-TOF mass spectrometry, while antimicrobial susceptibility testing (AST) was performed via broth microdilution in accordance with CLSI guidelines to determine minimum inhibitory concentrations (MICs) for a broad panel of commonly used antimicrobials in veterinary medicine. Multidrug resistance (MDR) was defined as resistance to at least one agent in three or more antimicrobial categories. Data on patient demographics, prior antimicrobial exposure, underlying comorbidities, and recent healthcare interactions were collected to assess risk factors for resistant infections. Initial results identified a diverse bacterial milieu with Escherichia coli, Proteus mirabilis, Klebsiella spp., and Staphylococcus pseudintermedius as predominant uropathogens. A concerning prevalence of ESBL-producing Enterobacterales and AmpC-producing organisms was observed, contributing to elevated MICs for third-generation cephalosporins and beta-lactam/beta-lactamase combinations. Fluoroquinolone resistance was detected in a substantial subset of Gram-negative isolates, correlating with prior fluoroquinolone exposure and prolonged disease duration. For Gram-positive pathogens, methicillin-resistant staphylococci were identified, limiting the efficacy of beta-lactams and prompting consideration of alternative agents. High rates of MDR isolates were associated with prior antimicrobial therapy, recurrent UTIs, and recent hospitalization, underscoring the impact of previous antimicrobial use on resistance selection. In response to AMR patterns, the study evaluated alternative therapeutic options through both in vitro and in vivo lenses. In vitro assessments included evaluating the minimum inhibitory concentrations of non-traditional agents and combinations, such as nitrofurantoin for lower urinary tract infections, fosfomycin, amikacin, and polymyxin B where appropriate, and potential synergistic interactions using checkerboard assays. The in vivo component involved a pilot clinical trial comparing standard-of-care regimens against an evidence-informed alternative protocol that prioritizes narrow-spectrum agents guided by AST results, optimized dosing strategies, and consideration of combination therapies for MDR infections. Pharmacokinetic/pharmacodynamic (PK/PD) modeling supported dosing regimens to maximize efficacy while minimizing resistance selection. Key findings indicate that AST-guided, targeted therapy significantly improved clinical resolution rates and reduced recurrence compared to empiric regimens, with a notable reduction in total antimicrobial exposure. The data corroborate the utility of nitrofurantoin and fosfomycin as viable oral options for lower UTIs caused by susceptible Enterobacterales, while highlighting the limitations of fluoroquinolones in the face of prevalent resistance. The study also emphasizes the necessity of antimicrobial stewardship in veterinary practice, including routine urine culture and sensitivity testing, judicious antimicrobial selection, and education of pet owners about adherence and preventive strategies. These results have implications for updating veterinary canine UTI treatment guidelines and for shaping regional surveillance programs to monitor evolving AMR trends in companion animals.

Project Overview

What This Project Is About

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A plain-language overview of how bacteria that infect dogs' bladder areas can resist common medicines, and how veterinarians might choose better treatments.

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The Problem It Addresses

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Urinary tract infections (UTIs) in dogs are common, but many bacteria are becoming harder to treat because they are resistant to standard antibiotics. This project looks at which bacteria are most resistant and why, helping vets pick effective medicines and reduce misuse.

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Objectives of the Project

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1. Identify the main bacteria causing canine UTIs in the study area.
2. Determine the antibiotic resistance patterns of these bacteria.
3. Evaluate alternative drugs or strategies that could work when resistance is present.
4. Provide practical guidance for veterinarians on antibiotic choices.

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What You Will Do Step by Step

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1) Collect urine samples from dogs with UTIs under veterinary supervision.

2) Isolate bacteria from samples in the lab.

3) Test each isolate against a panel of commonly used antibiotics to see which ones work.

4) Analyze patterns to identify which bacteria resist which drugs.

5) Review alternative treatment options based on the findings and current guidelines.

6) Summarize practical recommendations for clinical use and responsible antibiotic stewardship.

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Expected Outcome

Clear data on which bacteria are most resistant in canine UTIs and which alternative therapies are effective, leading to improved treatment decisions and reduced antibiotic resistance in dogs.