Clinical Evaluation of a Centralized In-Clinic Direct Culture and Antimicrobial Susceptibility Testing Workflow for Canine and Feline Skin, Ear, and Urine Infections

Background/Objectives: Rapid antimicrobial decision-making in small-animal practice is limited by the turnaround time (≥2 days) of conventional laboratory-based culture and antimicrobial susceptibility testing (AST). Existing point-of-care and in-clinic tests can provide faster results, but their performance often depends on user experience. This study evaluated VetBac, a hybrid workflow in which the test is conducted in the clinic, while experts centrally interpret bacterial growth on plates. Methods: We analyzed 60 interpretable plates from canine and feline skin, ear, and urine infections. In the clinic, samples were inoculated onto chromogenic Mueller–Hinton agar plates, after which antibiotic discs were applied. Plates were incubated for 16–20 h, photographed, and interpreted centrally by an expert. For comparison, samples were submitted in parallel to standard microbiology laboratories. Results: Identification of primary bacterial populations in clinical samples showed high species-level agreement with laboratory results (83.9%), increasing to 100.0% when staphylococci species were grouped. Secondary bacteria agreement (16.7%) was lower due to unrecognizability and overgrowth by dominant bacteria. Overall AST agreement was 93.6% (262/280), with 91.9% sensitivity for detecting resistance and 94.0% specificity for detecting susceptibility. VetBac-susceptible discrepancies occurred in 5/62 laboratory-resistant comparisons (8.1%), and VetBac-resistant discrepancies occurred in 13/218 laboratory-susceptible comparisons (6.0%). Conclusions: In interpretable skin, ear, and urine samples, the VetBac workflow showed high agreement with laboratory results for primary bacterial identification and AST. These findings support the hybrid in-clinic/centralized model as an adjunctive source of earlier antimicrobial decision support, pending laboratory confirmation. However, the study did not estimate the proportion of all clinical samples suitable for direct culture and AST.