Fig. 4

Bacterial clearance in lung. Lungs were extracted from the mice subjected to the challenge test, and the pertussis bacterial colonies were enumerated at 2 h and 2, 5, and 8 days after the challenge. Four mice were sacrificed at each time points. By Day 5 post-challenge, the bacterial colonies were hardly found in any of the groups, with the exception of the negative control group, which was injected with saline solution