Class of serum antibodies towards Salmonella enteritidis in gastro-enteritis, as measured by mixed reverse passive antiglobulin haemagglutination (MRPAH).

Sera taken from a well-mapped epidemic of Salmonella enteritidis gastro-enteritis among school children and teachers have been tested for antibodies of the IgG, IgM and IgA classes by MRPAH (mixed reverse passive antiglobulin haemagglutination) and for IgG and IgM classes by ELISA. When suitable threshold titres were chosen all sera taken up to 10 days after infection were negative by MRPAH, whereas all samples but one taken between day 16 and 48 showed the presence of antibodies of each three immunoglobulin classes. IgG antibody titres often remained elevated one year after infection whereas IgM and particularly IgA antibodies returned to negative. Up to the 28th day the IgG antibody titre showed a logarithmic increase with time, whereas no simple relationship was observed for the IgM and IgA antibody responses. Estimation of the regression equations for the titres measured by ELISA and MRPAH shows agreement between the two methods.