The invention relates to an antimicrobial composition comprising at least one water soluble or water dispersable source of zinc ions in combination with at least one water soluble or water dispersable source of lithium ions and optionally at least one water soluble or water dispersable source of magnesium ions and/or at least one water soluble or water dispersable source of sodium ions, an aqueous preparation, a process for preserving an aqueous preparation against microorganisms as well as the use of the antimicrobial composition for preserving an aqueous preparation against microorganisms.