Adherence inhibition assay: a specific serological test for detection of antibodies to Mycoplasma pneumoniae.

Antibodies directed against the adherence-mediating protein of Mycoplasma pneumoniae were measured by an adherence inhibition assay. Pretreatment with antibody-containing sera reduced the attachment of sheep erythrocytes to Mycoplasma pneumoniae layers grown in flat-bottom microtiter plates. The degree of attachment of erythrocytes was estimated by lysis with distilled water and measurement of absorbance in a microtiter reader. Sera tested included 126 sera from patients with suspected Mycoplasma pneumoniae respiratory infection and 60 sera from patients with serologically confirmed respiratory infection of other origin. Examination of human sera by both complement fixation using glycolipid as antigen, and the adherence inhibition assay indicated a high degree of specificity of the latter. Furthermore, titer increases parallel to complement fixation titers were found in six paired sera, and testing of separated IgM showed high reactivity in this immunoglobulin fraction. The adherence inhibition assay is a reproducible method which is relatively easy to perform. It may be of importance especially when a non-specific complement fixation reaction due to cross-reaction is suspected.