P1830 Susceptibility of Gram-positive pathogens to daptomycin and other antimicrobial agents: first results from the DAPTOGERM Surveillance Study

Abstract

Revised Abstract Objectives: Drug resistance in Gram-positive bacteria has become an increasing problem over the past 20 years. New antibacterial agents such as the lipopeptide daptomycin (DAP), which was recently approved in the EU, have been developed to address this problem. Shortly after the approval, a surveillance study was started by a network of clinical microbiology laboratories to monitor the susceptibility of Gram-positive pathogens to DAP in Germany. This report comprises the results of isolates of five frequently encountered Gram-positive species collected in 49 laboratories from March to June 2006. Methods: A total of 1,520 isolates including oxacillin-susceptible Staphylococcus aureus (MSSA, n=360), oxacillin-resistant S. aureus (MRSA, n=286), Staphylococcus epidermidis (Se, n=262), Enterococcus faecalis (Es, n=209), Enterococcus faecium (Em, n=208), and Streptococcus pyogenes (Sp, n=195) were tested against DAP, linezolid (LZD), vancomycin (VAN) and other drugs. First isolates obtained from hospitalized patients with skin and soft tissue infections, respiratory tract infections, foreign body/catheter infections, or sepsis were included. MICs were determined in a central laboratory using the broth microdilution procedure according to the standard of the German DIN (Deutsches Institut fur Normung) 58940 guidelines. MICs of DAP were interpreted by the EUCAST criteria. Results: The majority of isolates was recovered from wound swabs (57.7%), blood samples (21.9%) and respiratory tract specimens (8.2%). MIC50/90 values of DAP for MSSA, MRSA, and Se each were 0.5/1 mg/L. All strains were inhibited by DAP at the EUCAST breakpoint of ≤1 mg/L. LZD and VAN were also active against all staphylococci. However, based on MIC50/90 values, DAP was up to 4fold more active than LZD or VAN. Of the Em isolates, 23 (11.1%) were resistant to VAN. In contrast, none of the Es isolates exhibited resistance to VAN. DAP inhibited all strains at 4 mg/L. MIC50/90 values of DAP for either enterococcal species were 2/4 mg/L. One Es strain was resistant to LZD (MIC 32 mg/L). DAP was more active than LZD or VAN against Sp. MIC50/90 values were 0.125/0.25 for DAP compared to 0.25/0.5 and 1/1 for VAN and LZD, respectively. The highest MICs of DAP for Sp isolates were 0.5 mg/L. Conclusion: DAP demonstrated excellent in vitro activity against frequently encountered Gram-positive species including multi-resistant isolates such as MRSA and VRE. Resistant strains were not detected.