Antibody formation in rabbits after vaccination with Streptococcus pyogenes cultured in the presence of subinhibitory concentrations of erythromycin

: Rabbits were immunized with suspensions of Streptococcus pyogenes grown, either in the presence of subinhibitory concentrations of erythromycin (1/2 and 1/8 MIC) or without antibiotic. Over a twelve-week period, the opsonic activity of the serum and the levels of various streptococcal antibodies were determined. For the two test strains, the immune response observed was identical for the vaccine grown with 1/8 MIC erythromycin and for the control vaccine. The vaccines grown with 1/2 MIC of erythromycin induced a slower and weaker elaboration of protective antibodies.