Emergence of Vancomycin-Intermediate Staphylococcus aureus and S. sciuri, Greece

and specific detection of verotoxin genes in Escherichia coli by the polymerase chain reaction. TE. Detection and characterization of the eae gene of Shiga-like toxin-producing Escherichia coli using polymerase chain reaction. To the Editor: Staphylococcal isolates with reduced susceptibility to glycopeptides, such as vancomycin and teicoplanin, are a serious public health problem because staphylococci frequently show multidrug resistance, and glycopeptides are the only remaining effective drugs. Since the early reports of glycopeptide-resistant staphylococci, teicoplanin resistance has become more common than van-comycin resistance, particularly among coagulase-negative staphylo-coccal species (1-3). In cases of staphylococci with reduced susceptibility to vancomycin (vancomycin-intermediate staphylococci), an increasing number of strains showing heterore-sistance are reported (strains that contain subpopulations of cells at frequencies >10-6 for which the van-comycin MICs are 8 µg/mL to 16 µg/ mL); homogeneous resistance still appears to be rare (2,4-7). In northern Greece, resistance to teicoplanin has recently been documented in S. haemolyticus strains isolated from clinical infections (8). We report the first bloodstream infections in Greece associated with S. aureus and S. sciuri strains that have homogeneous intermediate resistance to vancomycin (MIC = 8 µg/mL). In our department, all clinically significant staphylococcal isolates are screened for reduced susceptibility to vancomycin and teicoplanin by an agar incorporation method (9), which has been routinely performed since January 1999. An inoculum of 10 4 CFU/spot from a log-phase broth culture was spread on Mueller-Hinton agar plates containing appropriate antibiotic concentrations. The strains were incubated for a full 24 hours before the MICs were read. When a reduced susceptibility to vancomycin was observed (MIC 8 to 16 µg/mL), the test was repeated for confirmation of the result and the strains were also tested by National Committee for Clinical Laboratory Standards (NCCLS) broth microdilution (9) and E-test (AB Biodisk, Solna, Sweden) with BHI agar (Oxoid, Ltd., Basing-stoke, Hampshire, UK) and an inocu-lum density adjusted to 0.5 McFarland value. S. aureus ATCC 29213, which had MICs for vancomycin of 1 µg/mL and for teicoplanin of 0.5 µg/mL, was used as a control for the estimation of the MICs. Two vancomycin-intermediate staphylococcal isolates (one S. aureus and one S. sciuri) were recovered in our hospital during December 2000 and April 2001, respectively. The organisms were identified with the Vitek system (bioMerieux Vitek, La Balme les Grottes, France). Slide-coagulase test and Staph ID 32 API system (API system, bioMerieux) confirmed identification. Susceptibility to 18 antimicrobial agents was evaluated with the …