Presence of Staphylococcus aureus with reduced susceptibility to vancomycin in Germany

A total of 457 Staphylococcus aureus strains from the culture collection of the National Reference Center for Staphylococci in Bonn, Germany, were scr eened for susceptibility to vancomycin because some Staphylococcus aureus s trains are able to form subpopulations that show intermediate resistance to vancomycin. Two methicillin-resistant Staphylococcus aureus strains (isola ted in 1993) exhibited intermediate resistance. One of these, Staphylococcu s aureus 137-93, which displayed the genomic DNA fragment pattern of the no rthern German epidemic strain, appeared homogeneously resistant. Neither of these strains had been identified by routine susceptibility testing. The r esistance of the German isolates was lower than that of the Japanese isolat e Mu50. To determine whether a similar mechanism confers vancomycin resista nce in Staphylococcus aureus Mu50 and 137-93, the intracellular cell wall p recursor concentration was measured and was not found to be comparably incr eased in Staphylococcus aureus 137-93. In conclusion, strains showing inter mediate resistance have been present in Germany for some time (at least sin ce 1993), but the subpopulations with decreased sensitivity were overlooked during antibiotic susceptibility testing.