Absence of bacterial DNA in culture-negative urine from cats with and without lower urinary tract disease

Abstract

A diagnosis of bacterial cystitis commonly relies on a positive microbiological culture demonstrating the presence of a significant number of colony-forming units/ml urine, as urine within the upper urinary tract, bladder and proximal urethra generally is considered sterile. Recent studies from human and veterinary medicine indicate the presence of non-culturable bacteria in culture-negative urine samples. The aim of the present study was to determine the occurrence of bacterial DNA in culture-negative urine samples from cats with signs of feline lower urinary tract disease (FLUTD) and healthy control cats by 16S ribosomal DNA PCR and subsequent sequencing. The study sample included 38 culture-negative urine samples from cats with FLUTD and 43 culture-negative samples from control cats. Eight culture-positive urine samples from cats with FLUTD were included as external positive controls in addition to negative reaction controls. Of possible methodological limitations, degradation of DNA due to storage, the use of non-sedimented urine for DNA isolation and lack of internal positive reaction controls should be mentioned. The positive controls were recognised, but occurrence of bacterial DNA in culture-negative urine from cats with or without signs of lower urinary tract disease was not demonstrated. However, considering the possible methodological limitations, the presence of bacterial DNA in the urine of culture-negative FLUTD cats cannot be excluded based on the present results alone. Therefore, a prospective study reducing the possibility of degradation of DNA due to storage, in combination with modifications enhancing the chance of detecting even lower levels of bacterial DNA in culture-negative samples, seems warranted.

Recurrent episodes of feline lower urinary tract disease with different causes: possible clinical implications

“…26–30 In 2015, a study of bacterial DNA in culture-negative urine from cats with and without signs of FLUTD in Norway did not demonstrate the presence of unculturable bacteria as a common finding in either group of cats. 31 However, the sensitivity of the assays used may have precluded detection of very low levels of unculturable bacteria. 31…”

“…31 However, the sensitivity of the assays used may have precluded detection of very low levels of unculturable bacteria. 31…”

“…[26][27][28][29][30] In 2015, a study of bacterial DNA in culture-negative urine from cats with and without signs of FLUTD in Norway did not demonstrate the presence of unculturable bacteria as a common finding in either group of cats. 31 However, the sensitivity of the assays used may have precluded detection of very low levels of unculturable bacteria. 31 In both human and veterinary medicine, infectious agents are generally not considered to be the cause of the clinical signs present in patients with idiopathic cystitis, interstitial cystitis or related pain syndromes, but some evidence indicates an increased risk of developing infections among these patients.…”

“…31 However, the sensitivity of the assays used may have precluded detection of very low levels of unculturable bacteria. 31 In both human and veterinary medicine, infectious agents are generally not considered to be the cause of the clinical signs present in patients with idiopathic cystitis, interstitial cystitis or related pain syndromes, but some evidence indicates an increased risk of developing infections among these patients. 10,32 Further, the presence of various components in urine from patients with FIC or IC/BPS not found in urine from control cases hints at the possibility of intracellular microorganism as part of the aetiology.…”

Understanding feline idiopathic cystitis

“…Antimicrobial therapy: There is no evidence that occult bacterial infections play a role in FIC (Lund and others 2015) and one controlled study of the use of chloramphenicol showed no benefit (Barsanti and others 1982). …”