May urinary neutrophilic degeneration and intracellular bacteria predict urine culture outcome in canine suspected urinary tract infections?

In veterinary medicine, stained urinary sediment evaluation has shown higher diagnostic performance than wet-mount evaluation in diagno- sis of urinary tract infections (UTIs). For bronchoalveolar lavage and body cavity fluids, it is reported that degenerative neutrophil changes, and intracellular bacterial localization have known diagnostic rele- vance in evaluating the role of bacteria in inflammation. The aim of this prospective study is to evaluate associations between urine cul- ture and the detection of neutrophil morphological alterations or intracellular bacteria in stained urinary sediment in dogs with clinically suspected UTI. UTIs were suspected based on clinical history and clinical signs (such as pollakiuria, dysuria, and hematuria). Each dog had cystocentesis and underwent routine urinalysis with wet-mount sediment evaluation, urine culture, bacterial cell count and antibiotic-sensitivity test for their routine care for suspected UTI. Diff-Quik-stained cytospin sam- ples were microscopically evaluated for the presence/absence of neu- trophils and bacteria, neutrophil morphological alterations and bacterial localization (intra/extracellular). Urine culture with <100 colony-forming units were classified as negative. Presence/absence of degenerated neutrophils, bacteria and bacterial localization were com- pared between positive/negative urine culture using Fisher's exact test. Odds ratio (OR) was calculated. Forty-five dogs were prospectively included. Seventeen dogs (38%) had positive urine culture. Sixteen dogs showed bacteria at cytospin evaluation, of which 14 dogs had intracellular bacteria. Dogs showing cytologically-evident bacteria had a 19-fold chance to have positive urine culture (OR 19.5 95%CI 4.2-83-5;p<0.0001), which increases if intracellular bacteria were highlighted (OR 27 95%CI 5-108; p<0.0001). Twenty-two dogs showed neutrophils, in particular 19 dogs had degenerated neutrophils. Dogs having neutrophils had a 6-fold probability to have positive urine culture (95%CI 19-22; p=0.006), whereas if degenerated changes were present the OR=12 (95%CI 3-40; p=0.0005). Finally, the combination of degenerated neutrophils with intracellular bacteria was present in 16 dogs, (OR 27 95%CI 5-108; p<0.0001). Interestingly, 3 dogs (6.5%) with degenerated neutrophils and intracellular bacteria had negative urine culture. Based on our results, the probability to have urine culture positivity increases if intracellular bacteria and degenerated neutrophils areseen. Most importantly, in some cases it allows to identify an active infection even with negative urine culture. Their presence in stained- mount samples may help the clinician in the diagnostic process of dogs with suspected UTIs.