SPECIFICITY OF AN ANTISERUM AGAINST ERWINIA-CAROTOVORA SUBSP ATROSEPTICA IN INDIRECT ELISA

Attempts to differentiate Erwinia carotovora subsp. atroseptica (Eca) from Erwinia carotovora subsp. carotovora (Ecc) by indirect ELISA usin g polyclonal antisera against the former bacterium were unsuccessful. However, when bacterial cells were preincubated with an antiserum agai nst Eca serogroup I and excess serum washed away prior to coating on m icro-ELISA plates, specificity was improved. This modified indirect EL ISA was able to separate Eca serogroups I, XVIII and XXII from all the Ecc serogroups tested. Cross adsorption of the antiserum with Ecc ser ogroup XXIX resulted in greatly reduced absorbance values for all stra ins/serogroups except Eca serogroups I and XXII. Cross adsorption with the homologous Eca strain reduced absorbance values for all strains/s erogroups. It is suggested that the differentiation of Eca serogroups I and XXII obtained with the modified indirect ELISA could be attribut ed to the removal of antibodies cross reacting to soluble antigens and the retention of antibodies to specific cell surface antigens.