Methicillin-resistant Staphylococcus aureus (MRSA) in the German Democratic Republic. Incidence and strain-characteristics.

In GDR methicillin-resistance strains of S. Aureus only occur in connection with nosocomial infections with a comparably low incidence (about 2%). They are not found in outpatients. For the detection of MRSA the test on nutrient medium L4 with addition of 5% NaCl has proved successful. All of the MRSA exhibit a rather unique pattern of strain-characteristics; they are nontypable by the basic-set-phages and show a reaction with the experimental phage A 994. The MRSA are multiple drug-resistant (generally penicillins, cephalosporins, isoxyzolylpenicillins, oxytetracycline, minocycline, streptomycin, erythromycin, lincomycin and additionally chloramphenicol and gentamycin, kanamycin, tobramycin). The genetical characterization and the plasmid-pattern analysis has shown that only resistance to chloramphenicol and in one case also to macrolides are determined by plasmids (MW 2.0 and 1.8 Megadalton). The determinants for the other resistance-characters are obviously located on the chromosome. Altogether these data indicate that the MRSA described are derivatives of a single-strain-clone.