Antibodies to Major Outer Membrane Proteins of Escherichia coli in Urinary Infection in the Elderly

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Abstract
The serologic response to infection in elderly bacteriuric subjects and young women with acute pyelonephritis was measured with an enzyme-linked immunosorbent assay (ELISA) using the major outer membrane protein complex (MOMP) of one Escherichia coli strain as antigen. Elderly controls and subjects with asymptomatic bacteriuria had variable titers; control titers were significantly lower than those with asymptomatic bacteriuria. Titers were stable over 2–12 w in asyptomatic subjects. Elderly subjects with invasive infection and women with pyelonephritis demonstrated increases in titer between acute and convalescent serum for E. coli and other Enterobacteriaceae. With a convalescent specimen with an antibody titer ⩾3 standard deviations (SD) above the acute, the sensitivity of the MOMP ELISA for identifying invasive infection was 74%, the specificity 86%, the positive predictive value 82%, and the negative predictive value 79%. With the criteria of ⩾3 SD or an initial serum to control ratio of ⩾15 these parameters were 95%, 82%, 82%, and 95%, respectively. These initial investigations suggest the MOMP of E. coli may be an antigen with wide cross-reactivity, suitable for use as an objective test to identify invasive Enterobacteriaceae urinary infection.