Changing pattern of phage group II Staphylococcus aureus infections: from community to hospital.

Changes in Staphylococcus aureus strains of phage group II were evaluated over a 30-year period. Strains of this group were previously known to be mainly community-acquired, to be rather sensitive to antibiotics and to occur in infections with better clinical outcome. During the period 1961 to 1990 a total of 551,563 S. aureus strains was characterized according to antibiotic resistance, phage type and site of isolation. Clinical information was obtained on 16,781 bacteraemia cases. Strains of group II occurred until 1983 with a rather constant frequency around 16% of the S. aureus population. Since then, a constant increase in frequency has taken place and since 1990 they are the most frequently isolated phage pattern (22%). Bacteraemia caused by these strains occurs today with the same frequency in hospital and community as strains of other phage patterns. Moreover, these strains have changed from being highly susceptible, to being more resistant to penicillins and tetracycline than the rest of the population. Resistance to methicillin remained low in group II strains throughout the period (about 0.2%). Mortality rate and the proportion of patients with underlying diseases have been the same in recent years regarding group II strains as with other strains. This study indicates that the previous distinction between community acquired and hospital-acquired S. aureus infections is no longer valid.