Samantha J Guida, Joseph Bartges, Rebekah Jones, Caleb Young, Maria Cekanova
Conventional aerobic microbial urine culture with antimicrobial susceptibility testing (UCS) is reference standard for diagnosis of canine Bacterial Urinary Tract Infections (BUTIs). Emerging multiplex real-time PCR (qPCR) may be a useful diagnostic test when performed in conjunction with UCS. The aim of this study was to compare qPCR with UCS for identification of uropathogens in canine urine. Twenty-three frozen isolates of canine uropathogens were selected from an archive and grown on blood agar plates. Following growth on blood agar, colonies from each isolate were inoculated into sterile canine urine, creating 23 positive contrived urine specimens. Urine specimens were incubated for 40 hours at 38°C. Samples were split into two sets of 23 specimens; the first set was analyzed by UCS, and the second set was analyzed by qPCR. Two specimens of sterile urine were used as negative controls. Blind urine sample testing was performed at both analytical laboratories.
UCS correctly identified uropathogens in 22 of 23 positive isolates. qPCR correctly identified uropathogens in 20 of 23 isolates. Controls did not yield bacterial growth. One sample containing Staphylococcus schleiferi was identified by UCS, but not qPCR; however, qPCR detected unspecified uropathogen by presence of 16S RNA. In 3 samples, qPCR identified an additional organism that was not detected by UCS. qPCR had comparable results to UCS for identification of canine uropathogens from frozen isolates. If similar results are seen in urine from dogs with naturally occurring urinary tract infections, qPCR may serve as a useful adjunctive diagnostic tool.