[New bacteriological results with Co-trimoxazole (author's transl)]

The current situation regarding resistance to cotrimoxazole and trimethoprim as well as the selected ratio of our combination and the resulting proportions of the two components in body fluids and tissues are discussed. Special attention will be paid to the relevant synergy in the respective proportions. Data on the development of resistance towards co-trimoxazole obtained from London, Zurich, Hamburg and Austria will be presented. In general, however, in Zurich a slight increase in resistance to staphylococci, Klebsiellae and Serratia can be seen. If we take an investigation in Hamburg as an example, we can show the importance of distinguishing between infectious hospitalism and a genuine development of resistance. Reference is made to Austria, because of claims that the resistance problem would be improved by combination with another sulfonamide (sulfametrole). The situation in Austria resembles that in Zurich. In order to deal with the problem as to whether the risk of the development of resistance to co-trimoxazole is still as significant as 10 years ago, the resistance frequency towards TMP alone will be further analysed. The chromosomal as well as the plasmidic transferable resistance is on slight increase in England, France and Italy. However, susceptibility to the combination has not yet adversely influenced. Accelerated deterioration of the susceptibility could occur if TMP alone were introduced in more countries. However, 30-50% of TMP-resistant organisms are still susceptible to sulfonamides and remain therefore sensitive to a strong synergistic influence of the combination, which is shown in many instances. As a result of various chemico-physical properties different ratios of both components, SMZ and TMP occur, in body fluids and tissues which differ from that in the plasma. However, many of these ratios are comprised by the large range of potentiation of the combination against many pathogens. A more complete synergistic inhibition however, would be achieved by the development of new supplementary combinations.