Notably, an opsonophagocytic mouse mAb that protected against ST3 sepsis and pneumonia did not reduce ST3 colonization, whereas a nonopsonic mAb agglutinated ST3, reduced colonization, protected against sepsis and pneumonia, and altered ST3 gene expression in vitro and in vivo (11, 13, 16). Here, MMP11 is linked to susceptibility to pneumonia measurement.