Is it necessary to test for cure during therapy for urinary tract infection (UTI)?
Each year in this country, UTI is diagnosed and treated in numerous children younger than 18 years; some are hospitalized as a result. Affected children have positive urine cultures and are treated with antibiotics. Is it necessary to prove that the infection is being cured by repeating the urine culture after 48 hours of treatment?
This is the question raised by Oreskovic and Sembrano1 in a recent paper published in Pediatrics. The authors conducted a retrospective chart review of 328 patients under age 19 who were hospitalized with UTI during a 6-year period. Their goal was to determine the frequency of positive cultures after 2 days of treatment. The authors included patients who had a positive urine culture on admission and who had a repeat culture done 2 to 3 days after admission. Cultures were considered positive if they had more than 100,000 colony-forming units (CFU)/mL of a single organism on a clean-catch specimen, more than 10,000 CFU/mL of a single organism on a catheterized specimen, or any number of a single organism on a specimen from a suprapubic aspiration.
Of the 328 patients, a second urine culture was positive in only 1. This patient was a 7-month-old infant who had been admitted with bronchiolitis and a UTI and who was treated with trimethoprim(/sulfamethoxazole (TMP/SMX) for the UTI. While the initial culture showed more than 100,000 CFU/mL of Escherichia coli resistant to TMP/SMX, results were not available until after the second culture. A second-generation cephalosporin was substituted, and results of the repeat culture were negative after 2 days of treatment with that drug.
According to the American Academy of Pediatrics practice parameters on UTIs,2 when a patient is responding well to antibiotic therapy--and it is known that the organism is sensitive to the chosen antibiotic--a routine test for cure is not necessary. The same guidelines state that if a patient 2 months to 2 years old is not responding as expected, a repeat urine culture should be performed. As Oreskovic and Sembrano point out, several other studies have also supported the abandonment of routine testing for cure. Nevertheless, testing for cure of UTI remains a common practice.
A repeat culture increases the cost of medical care and, in the case of catheterization, patient discomfort. These effects would be justifiable if there were a medical necessity for the practice. However, there is very low, if any, yield in repeating a urine culture to test for cure when the patient is doing well.
It is important for physicians to be aware of changing resistance patterns, so that the chosen antibiotic is appropriate. When bacteria are identified on an initial culture, sensitivities need to be examined so that therapy for children infected with resistant organisms can be altered. If the patient's health does not improve with antibiotic therapy, a repeat culture may be helpful.
The bottom line: for most children with UTI, a repeat culture is not needed to prove that the infection is being cured.