FIG. 1.
Naïve serum resistance of in vitro-grown B. pertussis strains in the presence of different concentrations of serum. B. pertussis liquid culture bacteria were grown to mid-log phase in SS broth. The bacteria were diluted to a concentration of 1 × 104 CFU/ml and treated with different concentrations of naïve rabbit serum for 1 h at 37°C. Serum resistance is expressed as the percentage of bacteria that survived; the error bars indicate standard errors. All samples were run in quadruplicate, and each strain was tested at least twice.