Fig. 5

Populations of chloramphenicol resistance proteins change over time. Predicted proteins found when fecal metagenomic libraries were screened on chloramphenicol-containing media were collapsed into 97 % ID clusters. Black boxes signify genes encoding a resistance protein that were identified in the fecal metagenome of a study subject at a given timepoint, while white or light gray squares indicate that the protein was not present. Proteins that were co-localized with a mobile genetic element are marked with an asterisk. Chloramphenicol acetyltransferases were found in all mothers and in five of the six infants at the final timepoint, but were qualitatively less common in infants at earlier timepoints. By contrast, multidrug efflux pumps were rare in mothers and in 11-month-old infants, but were commonly found in earlier samples