Sensitivity of <i>Bordetella pertussis</i> biofilms to polyvalent pertussis serum Eugene M. Zaytsev

Abstract

Aim. Study of the sensitivity of Bordetella pertussis biofilms to polyvalent pertussis serum.Materials and methods. The intensity of biofilm formation by strains of B. pertussis in round-bottomed polystyrene 96-well plates in the presence of polyvalent pertussis serum was estimated by staining with 0.1% gentian-violet solution. The serum titer was estimated as a highest dilution, which suppressed the growth of biofilm cultures.Results. Serum titers that completely suppressed the formation of biofilms by the studied strains ranged from : 1,000 to 1 : 20,000. Vaccine strain No. 475a (serotype 1.2.3) was characterized by the highest sensitivity to serum, the titer of which was 1 : 20,000. Vaccine strain No. 305 (serotype 1.2.0) and strains isolated from whooping cough patients in the period from 2001 to 2010: No. 287 (serotype 1.0.3), No. 178 (serotype 1.2.0), No. 317 (serotype 1.2.3) were sensitive to serum in the titers 1 : 1,000-1 : 2,000. Vaccine strain No. 703 (serotype 1.0.3) was resistant to all serum dilutions studied. When sowing supernatants from wells with biofilms on a dense nutrient medium, the growth of colonies typical for B. pertussis was observed. Similar results were obtained when seeding the supernatants of the cultures from the wells with no biofilm.Conclusion. These data indicate that B. pertussis strains are heterogeneous in sensitivity to pertussis serum. The growth of colonies typical for B. pertussis when culture supernatants are sown on a dense nutrient medium, in the absence of biofilms in the wells, indicates that the biofilm formation is suppressed by inhibiting the adhesion of microbial cells on the substrate, and not due to the bactericidal action of the serum.