A compound of formula I: or a pharmaceutically acceptable salt thereof, wherein: R 1 is -C X, wherein X is independently a protecting group, a halogen, R, - OR, -SR, -N 2, a substituted or unsubstituted hydrazine, a substituted or unsubstituted 6-10 membered aryl ring, a substituted or unsubstituted 5-6 membered heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur; -NO 2; -PO 3 H; -SO 3 H; -CN; substituted or unsubstituted heteroaryl; or one of the following moieties: wherein each R is independently hydrogen or an optionally substituted group selected from C 1-6 aliphatic, C 1-6 heteroaliphatic, aryl, heteroaryl, or a cyclic radical; R 2 is a substituted or unsubstituted, branched or unbranched C 10 -C 25 aliphatic moiety; R 3 is -NH 2, a peptide, or -N(R 4)(R 5); R 4 is hydrogen or an optionally substituted group selected from C 1-6 aliphatic, C 1-6 heteroaliphatic, a cyclic radical, aryl or heteroaryl; R 5 is heteroaryl; -C(=N-R 6)(R 7), wherein R 6 is selected from hydrogen, aliphatic, and -N 2, and R 7 is selected from hydrogen, aliphatic, aryl, cyano, and - SO 2 R; or C LR 8, wherein L is a covalent bond or a bivalent, branched or unbranched, saturated or unsaturated, C 2 -C 6 hydrocarbon chain wherein one or more methylene units of L is independently replaced by -O-, -S-, -NH-, -C -, -C(=CH 2)-, or C 3 -C 6 cycloalkylene, wherein L is optionally substituted by one or more groups selected from halogen, phenyl, an 8-10 membered bicyclic aryl ring, a 5-6 membered heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 5- to 7-membered monocyclic having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur or a 7-10 membered bicyclic heterocyclyl ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur; and R 8 is -R, -OR, -N 2, a cyclic radical, aryl, heteroaryl, wherein each R is independently hydrogen or an optionally substituted group selected from C 1-6 aliphatic, C 1-6 heteroaliphatic, aryl, heteroaryl, or a cyclic radical; or a substituted or unsubstituted peptidic moiety; and Z is -S-, -O-, -NH-, -Se-, -S(=O)-, -S(=N)-, -S0 2 -, -Se(=O)-, or -SeO 2 -; for use as an antibacterial agent in the prevention and/or treatment of an epithelial condition caused or aggravated by bacteria in animals. R 1 is -C X, wherein X is independently a protecting group, a halogen, R, - OR, -SR, -N 2, a substituted or unsubstituted hydrazine, a substituted or unsubstituted 6-10 membered aryl ring, a substituted or unsubstituted 5-6 membered heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur; -NO 2; -PO 3 H; -SO 3 H; -CN; substituted or unsubstituted heteroaryl; or one of the following moieties: wherein each R is independently hydrogen or an optionally substituted group selected from C 1-6 aliphatic, C 1-6 heteroaliphatic, aryl, heteroaryl, or a cyclic radical; R 2 is a substituted or unsubstituted, branched or unbranched C 10 -C 25 aliphatic moiety; R 3 is -NH 2, a peptide, or -N(R 4)(R 5); R 4 is hydrogen or an optionally substituted group selected from C 1-6 aliphatic, C 1-6 heteroaliphatic, a cyclic radical, aryl or heteroaryl; R 5 is heteroaryl; -C(=N-R 6)(R 7), wherein R 6 is selected from hydrogen, aliphatic, and -N 2, and R 7 is selected from hydrogen, aliphatic, aryl, cyano, and - SO 2 R; or C LR 8, wherein L is a covalent bond or a bivalent, branched or unbranched, saturated or unsaturated, C 2 -C 6 hydrocarbon chain wherein one or more methylene units of L is independently replaced by -O-, -S-, -NH-, -C -, -C(=CH 2)-, or C 3 -C 6 cycloalkylene, wherein L is optionally substituted by one or more groups selected from halogen, phenyl, an 8-10 membered bicyclic aryl ring, a 5-6 membered heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 5- to 7-membered monocyclic having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur or a 7-10 membered bicyclic heterocyclyl ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur; and R 8 is -R, -OR, -N 2, a cyclic radical, aryl, heteroaryl, wherein each R is independently hydrogen or an optionally substituted group selected from C 1-6 aliphatic, C 1-6 heteroaliphatic, aryl, heteroaryl, or a cyclic radical; or a substituted or unsubstituted peptidic moiety; and Z is -S-, -O-, -NH-, -Se-, -S(=O)-, -S(=N)-, -S0 2 -, -Se(=O)-, or -SeO 2 -;