Bactericidal formulations for use in veterinary medicine

A method of treating livestock infected with, or protecting livestock against infection from, bacteria which comprises administering to such livestock an antibacterially effective amount of a quinolonecarboxylic acid or derivative of the formula ##STR1## in which A represents nitrogen or C--R4,

R4 represents hydrogen, fluorine, chlorine, nitro or methyl,

B represents ##STR2## and B also represents ##STR3## when R1 does not denote cyclopropyl, and R5 represents hydrogen, a branched or unbranched alkyl group which has 1 to 4 carbon atoms and which can optionally be substituted by a hydroxyl or methoxy group,

R6 represents hydrogen, methyl or phenyl,

R7 represents hydrogen or methyl,

R8 represents amino, alkyl- or dialkylamino having 1 or 2 carbon atoms in the alkyl group, aminomethyl, alkyl- or dialkylaminomethyl having 1 or 2 carbon atoms in the alkyl group,

R1 represents an alkyl radical having 1 to 3 carbon atoms, cyclopropyl, 2-fluoroethyl vinyl, methoxy, 4-fluorophenyl or methylamino,

R2 represents hydrogen, alkyl having 1 to 6 carbon atoms, and cyclohexyl, benzyl, 2-oxopropyl, phenacyl and ethoxycarbonylmethyl,

R3 represents hydrogen, methyl or ethyl, Z represents oxygen, nitrogen which is substituted by methyl or phenyl, and CH2 --,

or a pharmaceutically utilizable salt thereof.