[Criteria for the establishment of limits for antibacterial chemotherapy]

The safety of patients asks for stringent standards when fixing limit values of the minimal inhibition concentration (MIC) in mg/l. It should be possible to recognize resistant bacterial strains with a low error on the basis of the recommendations of the bacteriological laboratory which are eventually important for therapy. Attention is drawn to the use of recognized methods such as DIN 58940 and 58944 and the participation in interlaboratory studies. Only such bacteria should be interpreted as "susceptible" whose MIC's are reliably below or, which is even better, much below the generally recognized average blood and tissue levels. Thus the break-points for the rating "susceptible" must be within the range of low variation. As a result, a few strains more would come within the "moderately susceptible" range. This would not exclude them from being selected if chemotherapy is performed with a correspondingly higher dosage (provided it is tolerated). Information on the chances of a success of therapy is improved in this way. A generous interpretation of pharmacokinetic data will in the end be more to the patient's detriment. In addition, there are numerous factors determining success or failure of therapy which cannot be established in vitro so that it is advisable to fix laboratory parameters in a stringent manner like that applied in the annexes (evaluation steps) to parts 3 and 4 of DIN 58940.