Teichoic acid antibody determination by agar-gel diffusion: effect of using dilute antigen preparations.

Abstract

Because the reported frequency of teichoic acid precipitins in controls and various patient groups has varied considerably among laboratories, we studied the effect of using various concentrations of staphylococcal extracts in agar-gel diffusion tests for teichoic acid antibodies. Of 25 normal sera, only 1 was positive against an undiluted extract, but 4 were positive against a 16-fold-diluted extract. Of nine sera from patients with staphylococcal bacteremia, two were positive at a higher titer against the diluted extract. A false-positive serum against the undiluted extract had a twofold titer increase against the diluted extract. Because human immune serum globulin is generally used as a positive teichoic acid antibody control, the variability of five different lots was studied. Three lots ahd teichoic acid antibody titers of 1:4, whereas one each had titers of 1:2 and 1:8. Based on this study, we feel that staphylococcal extracts should not be diluted. If immune serum globulins are used to determine the adequacy of ultrasonic extracts, newly acquired globulin lots should be standarized against an ultrasonic extract of proven sensitivity and specificity.