A compound of formula (I), for use in (A) treating and/or preventing a bacterial infection, wherein the bacterial infection is caused by flagellated bacteria selected from Helicobacter spp. and Campylobacter spp. ; (B) treating a condition associated with the bacterial infection as defined in (A), wherein the condition is selected from peptic ulcer, gastritis, duodenitis, gastric mucosaassociated lymphoid tissue (MALT) lymphoma, enteritis, and enterocolitis; or (C) preventing a condition associated with the bacterial infection as defined in (A), wherein the condition is selected from peptic ulcer, gastritis, duodenitis, gastric (stomach) cancer, gastric MALT lymphoma, enteritis, and enterocolitis; and wherein in (A) to (C) a therapeutically effective amount of the compound is to be administered to a subject in need thereof, wherein the subject is a mammal, preferably a human, or other animal; and wherein: (a) X and Y of formula (I) are independently selected from N, O and S; (b) R 1 is: (b-1) phenyl, optionally substituted by one or more: (i) C 1-3 alkyl or isopropyl; and/or (ii) X or CX 3 (X is selected from Cl, Br, I and F); or (b-2) biphenyl; (c) R 2 is CX 3 or CH 2 CX 3 , where X is selected from H, F, Cl, Br and I; (d) R 3 is CH 2 SX, where X is H or C(NH)NH 2 ; (e) R 4 is selected from F, CI, Br and I; and (f) R 5 is O; and wherein the compound of formula (I) has an anti-motility activity on the bacteria. (A) treating and/or preventing a bacterial infection, wherein the bacterial infection is caused by flagellated bacteria selected from Helicobacter spp. and Campylobacter spp. ; (B) treating a condition associated with the bacterial infection as defined in (A), wherein the condition is selected from peptic ulcer, gastritis, duodenitis, gastric mucosaassociated lymphoid tissue (MALT) lymphoma, enteritis, and enterocolitis; or (C) preventing a condition associated with the bacterial infection as defined in (A), wherein the condition is selected from peptic ulcer, gastritis, duodenitis, gastric (stomach) cancer, gastric MALT lymphoma, enteritis, and enterocolitis; and wherein in (A) to (C) a therapeutically effective amount of the compound is to be administered to a subject in need thereof, wherein the subject is a mammal, preferably a human, or other animal; and wherein: (a) X and Y of formula (I) are independently selected from N, O and S; (b) R 1 is: (b-1) phenyl, optionally substituted by one or more: (i) C 1-3 alkyl or isopropyl; and/or (ii) X or CX 3 (X is selected from Cl, Br, I and F); or (b-2) biphenyl; (c) R 2 is CX 3 or CH 2 CX 3 , where X is selected from H, F, Cl, Br and I; (d) R 3 is CH 2 SX, where X is H or C(NH)NH 2 ; (e) R 4 is selected from F, CI, Br and I; and (f) R 5 is O; and (a) X and Y of formula (I) are independently selected from N, O and S; (b) R 1 is: (b-1) phenyl, optionally substituted by one or more: (i) C 1-3 alkyl or isopropyl; and/or (ii) X or CX 3 (X is selected from Cl, Br, I and F); or (b-2) biphenyl; (b-1) phenyl, optionally substituted by one or more: (i) C 1-3 alkyl or isopropyl; and/or (ii) X or CX 3 (X is selected from Cl, Br, I and F); or (i) C 1-3 alkyl or isopropyl; and/or (ii) X or CX 3 (X is selected from Cl, Br, I and F); or (b-2) biphenyl; (c) R 2 is CX 3 or CH 2 CX 3 , where X is selected from H, F, Cl, Br and I; (d) R 3 is CH 2 SX, where X is H or C(NH)NH 2 ; (e) R 4 is selected from F, CI, Br and I; and (f) R 5 is O; and wherein the compound of formula (I) has an anti-motility activity on the bacteria. <EOS>