Diagnosis of bacterial urinary tract infection: Utility of urine myeloperoxidase concentration to predict urine culture results in dogs

Abstract

Suspected bacterial urinary tract infections (UTI) are a common cause of overuse and misuse of antimicrobials. A bedside diagnostic test that could accurately predict urine culture results would prevent antimicrobial overuse, but accurate biomarkers have not yet been identified in veterinary medicine. The objective of this study was to evaluate urine myeloperoxidase (uMPO) as a rapidly available, accurate marker to predict urine culture results. We hypothesized that uMPO would be higher in dogs with a positive urine culture than in dogs with a negative urine culture, and that uMPO could be used to aid in the accurate diagnosis of significant bacteriuria. Urine samples were collected from a veterinary university clinical pathology lab. uMPO concentration was measured using a commercially available canine myeloperoxidase (MPO) enzyme-linked immunosorbent assay (ELISA). Following validation, samples from 98 dogs that had a urinalysis and urine culture performed as part of their diagnostic investigation were included. Forty-seven dogs had a negative urine culture and fifty-one dogs had a positive urine culture. uMPO levels were significantly higher in samples that had a positive culture (median 2.13 ng/ml; IQR 0.98-7.07) versus samples that had a negative culture (median 1.07 ng/ml; IQR 0.52-1.84)(p < 0.005). Based on receiver-operator characteristic, a cutoff of 0.55 ng/ml was chosen to maximize sensitivity and specificity. Using a cutoff of 0.55 ng/ml, uMPO had a sensitivity of 70% and specificity of 69% to determine the presence of a positive culture. However, the degree of overlap between groups may preclude the use of this test as a surrogate for urine culture in a clinical setting.

The endotoxin content of PM 2.5 and its relationship with oxidative stress biomarkers in urine after subchronic inhalation exposure in a rat model

“…An increase in plasma MPO has been related to ischemic heart disease since MPO oxidizes low-density lipoproteins (LDL), contributing to atherosclerotic plaque formation (Delporte et al 2013). However, its increase in urine has been a helpful biomarker in diagnosing bacterial infections in the urinary tract in a canine model (Smith et al 2020). In our case, having found its increased activity in urine throughout exposure to PM On the other hand, GGT activity showed a signi cant decrease after week 4 of exposure.…”

“…There are experimental ndings that OxS may be involved in the pathogenesis of different kidney diseases. Some OxS biomarkers have been used as indicators of kidney damage in bladder cancer , urinary tract infections (Smith et al 2020), tubular damage (McMahon, Koyner, and Murray 2010), and ischemia-induced acute kidney injury (Tsikas 2017). It has also been proposed that proximal oxidative metabolism in acute kidney injury may lead to chronic kidney disease (CKD).…”