Objective: To assess the frequency of spontaneous changes of bacterial strains in patients with untreated asymptomatic bacteriuria.
Design: Retrospective analysis of samples from all patients with renal scarring and random sample of patients with normal kidneys.
Setting: Outpatient clinic for children with urinary tract infections.
Patients: 54 Girls aged 3.3-15.5 years with untreated asymptomatic bacteriuria caused by Escherichia coli.
Intervention: None.
End point: Change in bacterial strain.
Measurements and results: Serotyping and electrophoretic analysis of sequential bacterial isolates, representing 151 patient years of untreated asymptomatic bacteriuria. A total of 24 changes of strain were identified. Eleven were related to medical interference such as treatment of other infections with antibiotics.
Conclusions: Spontaneous changes of strain were uncommon, one change in 11.6 patient years, and thus are not a characteristic feature of the course of asymptomatic bacteriuria.