Preparation of antiserums for use in the fluorescent antibody identification of certain plaque bacteria

The interaction of many factors involved in FA antiserum production determines the quality of each antiserum or conjugate prepared. Performance and physicochemical characteristics of 58 FA antiserums to S mutans currently in use suggested that many of these conjugates could have been improved by using the methods and evaluation procedures described in this symposium. Deficiencies in the conjugates included low titers, incomplete fractionation, inadequately labeled antibody, fluorochromed albumin, free fluorescein and cross-reactions. Titers ranged from 1:1 up to 1:4,000. Titers for S mutans serotype c conjugates were uniformly low. S mutans serotype c conjugates were prepared from antiserums produced using a modified immunization schedule. The schedule used both viable and killed whole cells and gave FA titers as high as 1:1,000 (adjusted to 10 mg protein/ml). Procedures presented in this paper and the report by Pittman and co-workers27 should permit direct FA serum titers of up to 1:1,000 for each of the recognized serotypes of S mutans. The availability of highly specific antiserums with adequate titers will advance the use of the FA technique to identify microorganisms directly in specimens, such as dental plaque.29,30 This technique could be used to study such phenomena as the transmission of microorganisms from person to person and the establishment of the oral flora. It could also be used in epidemiological studies and perhaps to monitor the effect of a therapeutic agent on microbial composition of dental plaque.