Abstract

Urinary tract infection (UTI) in most cases is accompanied by pain. However, in some cases, including asymptomatic bacteriuria (ASB), pain is absent and thus, cannot be characterized. A study with an animal UTI model to quantify pelvic pain showed that Escherichia coli (NU14 strains) isolated from urine of patients with acute UTI caused pain, while E. coli (83972 strains) isolated from urine of patients with ASB caused no pain. The difference in pain response was not related to bladder colonization or inflammation, but to lipopolysaccharde (LPS) and Toll-like receptor 4, which is an LPS receptor. As the association between interstitial cystitis (IC) and UTI was epidemiologically suggested, an experiment was performed to investigate whether repeated infection with uropathogenic E. coli (UPEC) causes chronic pain through central sensitization. The results showed that repeated infection with the wild type UPEC caused temporary pain, while repeated infection with UPEC (SΦ 874 strains) in the absence of O-antigen caused chronic pain. Chronic pain following UTI is related to voiding dysfunction and anxious/depressive behavior. These relationships are mediated by transient receptor potential vanilloid type 1 at the stage of pain development and by C-C chemokine receptor type 2 at the stage of pain maintenance. Based on these findings, temporary E. coli infection causes chronic pain, which is one of the characteristics of neuropathic pain. This pattern is similar with the symptoms of IC, supporting the possibility of infection as an etiology of IC.

• Keywords: Urinary tract infections; Pain; Interstitial cystitis