Antibodies to major outer membrane proteins of Escherichia coli in urinary infection in the elderly.

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 asymptomatic 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 greater than or equal to 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 greater than or equal to 3 SD or an initial serum to control ratio of greater than or equal to 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.