Urinary IgG and IgA Antibodies in Elderly Individuals with Bacteriuria

Abstract

We studied the urinary IgG and IgA antibody in elderly subjects without bacteriuria, with asymptomatic bacteriuria and symptomatic urinary infection. Elderly individuals with asymptomatic bacteriuria had significantly elevated antibody levels relative to controls. When followed up to 12 months with persistent bacteriuria, antibody levels tended to persist but were variable. In elderly women with elevated urinary antibody titers, site of infection tended to be localized to the kidney, but antibody levels within the control range occurred as frequently as elevated antibody levels for renal infection. Subjects with invasive urinary infection had significantly elevated antibody levels at onset of symptoms, with levels increased or decreased when repeated 2–4 weeks later. Further studies to clarify the clinical significance of these observations are necessary.

Asymptomatic Bacteriuria, Urinary Antibody, and Survival in the Institutionalized Elderly

“…Antibody developed to these antigens is widely cross‐reactive among the Enterobacteriaceae, the most common infecting organisms in the institutionalized bacteriuric elderly. The antibody level correlates with urinary antibody measured to the whole cell 14 . Thus, the antibody may potentially be used, as we have done in this study, as an assay to identify elderly bacteriuric subjects with a more vigorous local response to their infection.…”

“…Renal failure, however, occurred no more frequently in the elevated than normal antibody group. In addition, an earlier study has shown that while elderly asymptomatic bacteriuric women with elevated urinary antibody are likely to have renal infection, as localized by the Fairley bladder washout technique, only 50% of women with renal infection have elevated antibody levels 14 . Elevated urinary antibody in response to persistent bacteriuria may identify the elderly individual who has “aged” further immunologically or with greater immune dysregulation due to associated chronic diseases, 22 resulting in an inappropriate local immune and inflammatory response with detrimental effects to the host over prolonged time.…”

“…Aliquots of urine were filtered through a 0.45‐micron Millipore filter to remove cellular debris and frozen at −70°C until antibody testing. The methods for the enzyme‐linked immunosorbent assay have been previously described in detail 13 , 14 . The antigen is the major outer membrane protein (MOMP) of a bacteremic E. coli strain purified using standard methods of outer membrane preparation, excision from polyacrylamide gel of the porin and outer membrane protein A proteins, and electrolution.…”

“…Results are expressed as a ratio of the patient test specimen to pooled urines from non‐bacteriuric elderly controls, defined as no history of urinary infection, no antimicrobials within the previous 6 months, and a negative urine culture at specimen collection. Urinary antibody was considered elevated if the ratio to control was ≥4, a value two standard deviations above the mean control value 14 …”

“…Elderly individuals with invasive urinary infection, including bacteremia or fever, have an increase in serum antibody to the major outer membrane protein of E. coli , and those with asymptomatic bacteriuria tend to have increased serum antibody levels compared to controls 13 . To further characterize the local interaction between the host and infecting organism in the bacteriuric elderly, we measured urinary antibody to the major outer membrane protein of E. coli 14 . From 30% to 50% of different groups of asymptomatic elderly had elevated urinary immunoglobulin G antibody to the major outer membrane protein relative to controls.…”