Bordetella pertussis autoagglutination

We have found that some B. pertussis isolates exhibit autoagglutination (Agg) phenotype when cultured on a synthetic cyclodextrin solid medium. The Agg did not occur in the presence of MgSO4, Nicotinic acid or when the bacterium was cultured on Bordet-Gengou agar. To determine the causal factor in autoagglutination of B. pertussis, we first isolated the non-agglutination mutant (designated as BP300s) from the strong Agg clinical isolate (BP300) by repeating single colony isolation from supernatant. By whole genome sequencing, two point mutations were found.