Figure 4.

Minimum spanning tree based on MLVA of Dutch B. pertussis strains isolated from 1993 to 2004. Each circle represents a different MLVA-type, indicated by the number in the middle of the circle. The size of the circle is related to the number of isolates within the particular MLVA-type. Green and red colors indicate, respectively the ptxP1 and ptxP3 allele frequencies within MLVA. The distribution of the MLST types is shown in boxes for the most commonly found MLVA types. In some cases the MLST types are not 100% due to the fact that not all strains were types by MLST.