[Investigations made to test the demarcation line method (DLM) after Dienes for its suitability in the epidemiology of Proteus mirabilis (author's transl)].

In 1946, DIENES observed that non-identical Proteus-strains, when swarming towards each other, were froming distinctly demarcated lines ("DIENES' phenomenon", demarcation (=AGL) phenomenon). Strains of the same origin were amalgamating without demarcation. In 1970, STURDZA studied this phenomenon and commented on its relevance for the epidemiology of nosocomial Proteus-infections. An increased number of Proteus-infections in Berlin was the reason that this procedure was tested for epidemiological purposes. Approx. 300 Proteus mirabilis-strains, tested on normal meat fluid agar, could be divided into 52 AGL-groups. When tested by several investigators, the coordination to any AGL-group seemed to be very subjective. Consequently, a DNase-agar with o-toluidinblue as an indicator, as had been mentioned by CHAMBERS in 1975, was used in order to give a more exact demonstration of AGL. This resulted in a reduction from 52 to 42 AGL-groups. Another 140 newly isolated Proteus-strains belonged to the 42 known as well as to another 42 new AGL-groups. Whether these 84 AGL-groups possess the constancy which is imperative for practical purposes, is however, still rather doubtful.