Abstract: Pyridone carboxylic acid compounds or physiologically hydrolyzable esters thereof are provided which are represented by the formula: ##STR1## wherein R.sub.1 is a lower alkyl, a halogen-substituted lower alkyl, a lower alkenyl, a cycloalkyl, or a substituted- or unsubstituted-phenyl group; R.sub.2 is a hydrogen atom, or a lower alkyl or an amino group; A is a nitrogen atom or the group C-X wherein X is a hydrogen or a halogen atom, or an alkoxy group; and Z is a group having the formula: ##STR2## wherein n is 1 or 2; R.sub.3 and R.sub.4 each represent a hydrogen atom or a lower alkyl group, with proviso that, if n is 2, one of R.sub.3 and R.sub.4 is a hydrogen atom; R.sub.5 and R.sub.6 each represent a hydrogen atom, or a hydroxy, a lower alkoxy or an amino group which is unsubstituted or substituted by a lower alkyl group, with proviso that one of R.sub.5 and R.sub.6 is a hydrogen atom; and R.sub.7 is a hydrogen atom or a lower alkyl group.

Abstract: The present invention provides novel organic acid addition salts of a quinolone-carboxylic acid of formula (I) ##STR1## wherein Z is 5-oxotetrahydrofuran-2-carboxylic acid or 2-hydroxyglutaric acid. The salts are highly soluble in water and are thus suitable to prepare a stable injection in storage for a long period of time.

Abstract: Novel semi-synthetic cephalosporin derivatives having a fused pyridiniummethyl at 3-position of the cephem nucleus, pharmaceutically acceptable salts, physiologically hydrolizable esters or solvates thereof are disclosed. Also disclosed is a process for preparing the cephalosporin derivatives which comprises introducing a fused pyridiniummethyl substituent at 3-position of 7-.beta.-[(Z)-2-(2-aminothiazol-4-yl)-2-methoxyiminoacetamido]-3-cephem-ca rboxylic acid derivatives. The compounds of the present invention show potent antibacterial activities and a broad spectrum against both gram-positive and gram-negative bacteria.