When vets order blood cultures for dogs and what positive results mean

Abstract

BACKGROUND: Bacteremia has been associated with many diseases in dogs, but contemporary data from a large and diverse population are lacking. HYPOTHESIS/OBJECTIVES: Report reasons for blood culture, protocols used, and diseases associated with a positive result in a tertiary referral institution. We hypothesized that larger volumes of blood, lack of previous antimicrobial administration, and changes in hematologic variables would be associated with increased rates of microbiological growth. ANIMALS: A total of 279 dogs from which 323 blood culture results were available. METHODS: For 180 submissions, patient and blood culture protocol data at the time of specimen collection were collected prospectively using a survey form. For 143 submissions, data were retrospectively collected. RESULTS: Microbial growth was noted in 55/323 (17%) submissions, with 35/55 (63.6%) interpreted as clinically relevant growth and 20 (36.4%) interpreted as contamination, resulting in an overall positive rate of 10.8%. Specimen volume (p&#x2009;=&#x2009;0.01), white blood cell count (p&#x2009;<&#x2009;0.001), and neutrophil count (p&#x2009;=&#x2009;0.001) were positively associated with relevant growth. Diseases associated with relevant growth were suspected discospondylitis (30%, p&#x2009;=&#x2009;0.05) and illness while on immunosuppressive drugs (44%, p&#x2009;=&#x2009;0.004). Submissions performed to assess for bacteremia as a secondary cause of immune-mediated disease were less likely to yield relevant growth (0%, p&#x2009;=&#x2009;0.004) than those performed for other reasons. CONCLUSIONS AND CLINICAL IMPORTANCE: In this population, blood cultures were most likely to provide diagnostically useful information in dogs with suspected discospondylitis and those receiving immunosuppressive drugs. Specimen volume should be maximized to increase the likelihood of clinically relevant growth.