Use of a compound of formula I, or a pharmaceutically-acceptable derivative thereof, for the preparation of a medicament for treating a microbial infection, wherein the compound of formula I is represented by, those in which: E represents CH; R 1 represents -X-R 4a a substituent at the 3-position of the pyrrolidinyl ring; X represents a direct bond or -N -; R 4a represents; (a) C 1-2 alkyl, which alkyl group is substituted by one or more substituents selected from phenyl (which latter group is optionally substituted by one or more substituents selected from halo, CN, C 1-3 alkyl and OR 10a), or (b) phenyl (which latter group is optionally substituted by one or more substituents selected from halo, CN, C 1-3 alkyl and OR 10a); R 2 represents C 1-2 alkyl; R 3 represents one to four substituents on the fused benzene ring including at least one substituent at the 6-position of the quinoline ring system, selected from; (a) halo (e.g. chloro), (b) OR 8a, (c) N S 2 R 8f, (d) N (R 8h), (e) -N C R 8i, C N R 8i or (f) Het 6; R 8a to R 8i independently represent, at each occurrence, (a) C 1-4 alkyl optionally substituted by phenyl (which latter group is optionally substituted by one or more substituents selected from halo, CN, C 1-2 alkyl, methoxy, ethoxy and S 2 -(C 1-2 alkyl)) or Het 7, (b) phenyl (which latter group is optionally substituted by one or more substituents selected from halo, CN, C 1-2 alkyl, methoxy, ethoxy and S 2 -(C 1-2 alkyl)) or (e) Het 9; R 10a represents C 1-4 alkyl; Het 6 represents a 5- or 6-membered, fully saturated heterocyclic group containing one nitrogen atom (which atom forms the point of attachment of the Het 6 group to the rest of the molecule) and, optionally, one further heteroatom selected from oxygen and nitrogen, which heterocyclic group may be substituted by one or more substituents selected from halo, methyl, and =O; Het 7 to Het 9 independently represent 5- or 6-membered aromatic heterocyclic groups containing one to three heteroatoms selected from oxygen, nitrogen and/or sulfur, which heterocyclic groups may be substituted by one or more substituents selected from halo, CN and C 1-2 alkyl. E represents CH; R 1 represents -X-R 4a a substituent at the 3-position of the pyrrolidinyl ring; X represents a direct bond or -N -; R 4a represents; (a) C 1-2 alkyl, which alkyl group is substituted by one or more substituents selected from phenyl (which latter group is optionally substituted by one or more substituents selected from halo, CN, C 1-3 alkyl and OR 10a), or (b) phenyl (which latter group is optionally substituted by one or more substituents selected from halo, CN, C 1-3 alkyl and OR 10a); (a) C 1-2 alkyl, which alkyl group is substituted by one or more substituents selected from phenyl (which latter group is optionally substituted by one or more substituents selected from halo, CN, C 1-3 alkyl and OR 10a), or (b) phenyl (which latter group is optionally substituted by one or more substituents selected from halo, CN, C 1-3 alkyl and OR 10a); R 2 represents C 1-2 alkyl; R 3 represents one to four substituents on the fused benzene ring including at least one substituent at the 6-position of the quinoline ring system, selected from; (a) halo (e.g. chloro), (b) OR 8a, (c) N S 2 R 8f, (d) N (R 8h), (e) -N C R 8i, C N R 8i or (f) Het 6; (a) halo (e.g. chloro), (b) OR 8a, (c) N S 2 R 8f, (d) N (R 8h), (e) -N C R 8i, C N R 8i or (f) Het 6; R 8a to R 8i independently represent, at each occurrence, (a) C 1-4 alkyl optionally substituted by phenyl (which latter group is optionally substituted by one or more substituents selected from halo, CN, C 1-2 alkyl, methoxy, ethoxy and S 2 -(C 1-2 alkyl)) or Het 7, (b) phenyl (which latter group is optionally substituted by one or more substituents selected from halo, CN, C 1-2 alkyl, methoxy, ethoxy and S 2 -(C 1-2 alkyl)) or (e) Het 9; (a) C 1-4 alkyl optionally substituted by phenyl (which latter group is optionally substituted by one or more substituents selected from halo, CN, C 1-2 alkyl, methoxy, ethoxy and S 2 -(C 1-2 alkyl)) or Het 7, (b) phenyl (which latter group is optionally substituted by one or more substituents selected from halo, CN, C 1-2 alkyl, methoxy, ethoxy and S 2 -(C 1-2 alkyl)) or (e) Het 9; R 10a represents C 1-4 alkyl; Het 6 represents a 5- or 6-membered, fully saturated heterocyclic group containing one nitrogen atom (which atom forms the point of attachment of the Het 6 group to the rest of the molecule) and, optionally, one further heteroatom selected from oxygen and nitrogen, which heterocyclic group may be substituted by one or more substituents selected from halo, methyl, and =O; Het 7 to Het 9 independently represent 5- or 6-membered aromatic heterocyclic groups containing one to three heteroatoms selected from oxygen, nitrogen and/or sulfur, which heterocyclic groups may be substituted by one or more substituents selected from halo, CN and C 1-2 alkyl.