Disclosed are aqueous mycobacterial concentrate compositions at a pH in the range of 6 to 12 which comprises per 100% weight of a concentrate composition:a) from about 0.1% wt. to about 25% wt. of a germicidal cationic quaternary ammonium compound;b) from about 0.25% wt. to about 25% wt. of a solvent selected from: phenoxyalcohol, glycol ethers, or mixtures thereof; and,c) water.The concentrate compositions may be used in a ready to use form, or may be further diluted with water to form a disinfecting composition therefrom. The compositions may also include an effective amount of a pH adjusting agent, such as sodium hydroxide or triethanolamine. The compositions featuring reduced amounts of active constituents than those known to the art, and are particularly effective against Mycobacteriuin terrae.