[Drug resistance of phage types of Salmonella typhimurium (author's transl)].

Antimicrobial susceptibility testing (disk diffusion test) and phage typing (method according to Anderson, performed by Prof. Brandis, Bonn) of 703 strains of Salmonella typhimurium from humans, isolated in Essen and surrounding during 1972 to 1975, was performed to dertermine whether characteristic patterns of drug resistance were associated with a single phage type or not. The most frequently isolated phage types are phage type 17 (12.2%), 12 (10.1%), 49 (8.1%), 15a (5.7%), 2 (3,3%) and the untypable phage type (46.7%). Resistance to tetracycline (45%) was most common, followed by resistance to sulfanilamide (19%), ampicillin (9%), and chloramphenicol (7%). Resistance to other antimicrobial agents (trimethoprim/sulfamethoxazol, gentamicin, colistin) was quite rare. Antibiograms of different phage types were found to be different, not only as far as the ratio of sensitive to resistant strains is concerned, but also for the ratio single-resistant to multiple-resistant strains. These differences were found to be statistically significant (chi-square-test, table 2). Comparison of antimicrobial resistance to tetracycline showed, that the portion of resistant strains was about 70% for the untypable phage types, 40% for phage type 17 and 7% for phage type 12. Among isolates of the phage type 49 multiple resistance was most common. The combination of resistance determinants is specified in figure 3. A possible interrelation between resistance pattern and the presence of R-plasmids in isolated strains is discussed.