CPD and infection: Regarding the other activities, the multiple deficiency in S. Typhimurium of candidates like the amidases AmiA/AmiB/AmiC (cleavage of NAM-L-Ala) or the D,D-carboxypeptidases PBP4/PBP5/PBP6 /PBP6b/PBP7 (cleavage of D-Ala-D-Ala in stem peptide), results in gross morphological changes that prevent their usage in infection assays of cultured mammalian cells.