<p>Described is a substance or a substance mixture that is produced by a) growing pathogenic organisms of one type in the presence of an active substance effective against these pathogenic organisms, b) until pathogenic organisms resistant to this active substance (escape mutants) have developed, c) preparation of antiserums, by known methods, against these resistant pathogenic organisms (escape mutants) or epitopes of functional elements of the escape mutants. Described also are a screening process for identifying susbtances that are effective against pathogenic organisms as well as drugs against pathogenic organisms and their escape mutants.</p>
