Obvious lack of association between dynamics of epidemic methicillin-resistant Staphylococcus aureus in central...

During the past 8 years, changes in the prevalence and spread of different epidemic methicillin-resistant Staphylococcus aureus (MRSA) have been observed in central Europe, with the emergence of new strains possessing fewer resistance characters. This has also been demonstrated at the level of particular hospitals. Since variation in agr specificity type has been proposed as a possible reason for population dynamics in Staphylococcus aureus, the agr specificity groups of different epidemic MRSA strains were investigated by PCR using agr group-specific primers. Four of the "old" as well as two "new" epidemic strains exhibited agr specificity group I. One group of epidemic MRSA strains, which has been observed since the beginning of the 1990s, exhibited the agr specificity group II. Sequencing the variable part ( agrB-D-C) of the agr locus revealed only six relevant nucleotide changes within this region, with three of them modifying the Shine-Dalgarno sequence region of agrC. On the basis of the results obtained, it is proposed that the dynamics observed in the population of MRSA in Germany is not due to different agr group specificities in "old" and "new" epidemic clones.