Chronic bacteriuria is a common occurrence among spinal-cord injury patients and others with neuropathic bladders. If bacteria are present in the urinary tract, the patient may develop symptoms of infection or remain asymptomatic. We have compared virulence properties of 28 Escherichia coli isolates from patients with symptomatic urinary tract infections (UTI) and 29 E. coli isolates from patients with asymptomatic bacteriuria (ABU). Bacteria from patients with symptomatic UTI were more likely to be hemolytic than isolates from patients with ABU (P ‫؍‬ 0.05) or fecal isolates obtained from healthy volunteers (P < 0.001). Bacteria from patients with symptomatic UTI were also more likely than strains isolated from patients with ABU (P ‫؍‬ 0.08) or fecal strains (P < 0.001) to exhibit D-mannose-resistant hemagglutination of human erythrocytes. The results suggest that E. coli isolates from nonimmunocompromised patients who require intermittent catheterization and who develop symptomatic UTI may be distinguished from bacteria recovered from patients who remain asymptomatic and possibly from normal fecal E. coli.Urinary tract infection (UTI) is a frequent medical complication during the initial medical and rehabilitation period after spinal-cord injury (SCI) and traumatic brain injury (TBI) and continues to be a problem throughout the life of many spinalcord-injured individuals. The urine of patients with neuropathic bladders frequently contains bacteria, and Escherichia coli is among the most frequent bladder colonizers (1,5,6). These bacteria may produce symptoms of UTI or may produce only asymptomatic bacteriuria (ABU). Bacteria associated with ABU are often left untreated and may even be beneficial in preventing symptomatic infection by more virulent organisms (16). Little is known at present about the virulence properties of E. coli bacteria that cause symptomatic UTI in patients with neuropathic bladders or how these strains may differ from benign colonizing strains. In the present study, approved by the Institutional Review Board of the hospital at which it was performed, we investigated selected virulence properties of E. coli isolates from SCI and TBI patients with UTI and ABU. Our hypothesis was that E. coli isolates from patients with symptomatic UTI possess virulence properties that may be used to distinguish them from other E. coli strains. MATERIALS AND METHODSPatient characteristics. Subjects were selected from patients admitted to a rehabilitation hospital between January 1994 and December 1996 with a diagnosis of SCI or TBI who were treated with intermittent catheterization and acquired at least one colonization of the urinary tract with E. coli. Twenty-five patients developed 28 symptomatic UTIs due to E. coli during that time. Of these 16 males and 9 females, 4 had TBI and 21 had SCI (12 tetraplegics and 9 paraplegics); the mean age was 39 (range, 7 to 75). Twenty-seven patients were colonized 29 times with E. coli but remained asymptomatic. Of these 15 males and 12 females, 1 had TBI and 19 had SC...