Comparing DNA testing and culture for dog skin infection bacteria

Abstract

BACKGROUND: Bacterial identification and antimicrobial susceptibility testing is an important step in timely therapeutic decisions for canine superficial bacterial folliculitis (SBF), commonly caused by Staphylococcus pseudintermedius. Next-generation sequencing (NGS) offers the appeal of potentially expedited results with complete detection of bacterial organisms and associated resistance genes compared to culture. Limited studies exist comparing the two methodologies for clinical samples. HYPOTHESIS/OBJECTIVES: To compare and contrast genotypic and phenotypic methods for bacterial identification and antimicrobial susceptibility from cases of canine SBF. ANIMALS: Twenty-four client-owned dogs with lesions consistent with SBF were enrolled. MATERIALS AND METHODS: A sterile culturette swab was used to sample dogs with SBF lesions. The swab was rinsed in 0.9 mL of sterile phosphate-buffered saline and vortexed to create a homogenous solution. Two swabs for NGS laboratories (Labs) and one swab for culture (Culture Lab) were randomly sampled from this solution and submitted for bacterial identification and antimicrobial susceptibility. RESULTS: No statistical difference regarding turnaround time for NGS Labs compared to Culture Lab was found. NGS Lab 1 identified more organisms than NGS Lab 2 and Culture Lab, which were both statistically significant. There was no statistical difference in detection frequency for Staphylococcus spp. among all laboratories. There was poor agreement for the presence of meticillin resistance and most antimicrobials among all laboratories. CONCLUSIONS AND CLINICAL RELEVANCE: Utilisation of NGS as a replacement for traditional culture when sampling canine SBF lesions is not supported at this time.