Vera C, et al. - This research was conducted to determine the frequency and dynamics of acquisition and colonization of Pneumocystis jirovecii among neonates and mothers. Investigations revealed that the frequency of colonization by P. jirovecii was higher in newborns than in their respective progenitors. Colonization of both mothers and children was transitory. However, the mother of the newborn was not necessarily the source of primary infection.