Measurement of antibody to Mycoplasma hominis by an enzyme-linked immunoassay and detection of class-specific antibody responses in women with postpartum fever

Abstract

The standard conditions for detection of human IgG, IgM, and IgA antibodies to Mycoplasma hominis by an enzyme-linked immunosorbent assay (ELISA) were established with the use of a cell lysate antigen and alkaline phosphatase conjugates. Antigen was used at a concentration of 10 μg of protein per milliliter, sera were diluted 1:200, and conjugates were diluted 1:500. Agreement between cultured isolation of M. hominis from the lower genital tract and presence of antibody in 207 women was 71%, 82%, and 86% for IgG, IgM, and IgA, respectively. When the ELISA was compared with the mycoplasmacidal assay, an overall agreement of 81% occurred, with the majority of the discrepancies occurring in the ELISA-positive and mycoplasmacidal-negative category. A linear relationship between end point titer and the A400 value (ELISA or absorbance value at 400 nm) at a standard serum dilution was demonstrated for the IgG, IgM, and IgA classes. Although the ELISA was relatively independent of antigen heterogeneity, no single strain detected more than 87% of positive sera, thus suggesting that optimum detection of antibody to M. hominis by the ELISA will require use of antigen pools derived from multiple strains of M. hominis.