Epidemiology of resistance among gram-positive bacteria: with special reference to staphylococcal infections.

During the past 27-30 years the antibiotic-resistance patterns of Danish Staphylococcus aureus strains have changed from penicillin-, streptomycin-resistance, to multiple-resistance ending up today with resistance to penicillin only. These changes have mainly been due to the introduction of different clones with characteristic phage-patterns and antibiotic-resistance patterns; respectively, the penicillin-, streptomycin-resistant strains of the 52, 52A, 80, 81 complex; multiple-resistant strains of the 83A complex and strains of the 94, 96 complex and of type 95 resistant to penicillin only. At the same time, however, changes in antibiotic-resistance pattern within the 52, 52A, 80, 81 and the 83A complex have taken place, and today strains of these complexes are mainly penicillin-resistant only or fully susceptible. Comparison of hospital-acquired strains with community-acquired strains proves that differences are only seen in periods with many resistant strains; today in Denmark these two groups have identical phage-patterns and antibiotic-resistance patterns. The investigations are based on 486412 strains isolated and phage-typed in 1960-86 and on further examination of 12852 strains isolated from blood.