Antibody-coated bacteria as an indicator of the site of urinary tract infection in renal transplant recipients receiving immunosuppressive agents

Abstract

Distinguishing an infection in the upper urinary tract from one in the lower urinary tract is especially important in renal transplant patients. Although the presence of antibody-coated bacteria in the urine has been shown by others to be a reliable indication of an infection in the upper urinary tract, it was not known whether sufficient antibody to coat the bacteria would be produced in a renal transplant recipient undergoing immunosuppression. We used a fluorescent test for detecting antibody-coated bacteria in the urine to follow 80 renal transplant patients prospectively for six months. Antibody-coated bacteria were detected in specimens from four patients with a clinical picture compatible with, or histopathologic evidence of, pyelonephritis. The origin of bacteriuria in a fifth patient was indeterminate both clinically and by the fluorescent antibody test. Twenty-three other patients with bacteriuria without clinical or histopathologic evidence of pyelonephritis had negative tests for antibody-coated bacteria. One patient with pyelonephritis in her own end-stage kidney had persistent bacteriuria with a negative fluorescent antibody test. Her transplanted kidney, however, was not infected. A positive test for antibody-coated bacteria is judged useful in distinguishing an infection in the upper urinary tract from one in the lower urinary tract in the presence of immunosuppression; however, the small number of cases and the methods used do not allow us to draw a conclusion about the significance of a negative result in a population undergoing immunosuppression.