How to culture dog urine samples for infection testing

Abstract

OBJECTIVE: To demonstrate a technique for plating and incubating canine urine cultures in-house as a screening tool for bacteriuria. ANIMALS: Urine samples from dogs presenting for urinary conditions. METHODS: The clinic's laboratory space should comply with biosafety level 2 requirements. Urine samples should be collected via cystocentesis or sterile urinary catheter. A sterile 1-µL inoculating loop is used to streak the urine onto both sides of a tryptic soy agar with 5% sheep's blood and MacConkey agar biplate. The plate is kept in a benchtop incubator at 35 to 37 °C for 16 to 24 hours, then checked for growth. Positive plates may be submitted to a reference laboratory for species identification and susceptibility testing. Alternatively, following identification of in-house bacterial growth, a urine sample stored in the refrigerator for no longer than 48 hours may be submitted for culture and susceptibility (C&S) testing. RESULTS: In-house urine culture provides an inexpensive way to accurately rule out bacteriuria as a cause for urinary conditions in dogs. CLINICAL RELEVANCE: The majority (70% to 80%) of canine urine cultures yield no growth. In patients with suspected urinary tract disease, avoiding reference laboratory C&S submission for negative samples allows client resources to be directed to additional diagnostics and treatments. In-house urine culture is an inexpensive screening tool for bacteriuria, which promotes antimicrobial stewardship, responsible use of client resources, and access to veterinary care. Positive in-house culture plates may still be accurately submitted for C&S once growth is confirmed.