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Reliability of daptomycin E-test strips for susceptibility testing

Abstract number: p1309

Cantón  R., Bille  J., MacGowan  A., Nord  C.E., Schito  G., Seifert  H., Soussy  C., Struelens  M., Verhoef  J., Morrissey  I.

Objectives: 

Daptomycin (DAP) is a new cyclic lipopeptide antibiotic active against Gram-positive bacteria. Approval is being sought in Europe for the treatment of complicated skin and skin-structure infections. This study compared local laboratory DAP susceptibility testing by E-test (ET) with central reference broth microdilution methodology (BM).

Methods: 

Staphylococcus aureus (SA) and coagulase-negative Staphylococci (CNS), including methicillin resistant strains, Enterococcus faecalis (Efc) and E. faecium (Efm), including vancomycin (VAN) resistant strains, Streptococci (Str) and corynebacteria (Cor) were collected by 81 centres in Austria, Belgium, France, Germany, Ireland, Italy, Netherlands, Portugal, Spain, Sweden, Switzerland and UK (October 2004–March 2005). ET MIC for DAP (ET strip supplemented with Ca2+), teicoplanin (TEI) and VAN was determined using local methods. MIC was repeated in a central lab using CLSI BM. CLSI breakpoints were used but TEI EUCAST and SA CLSI breakpoints were applied for Str and Cor, respectively.

Results: 

Complete categorical agreement for DAP, TEI and VAN was 94.7%, 95.2% and 98.7% respectively. False susceptible (S) (DAP, TEI or VAN BM non-susceptible but ET susceptible) and false resistant (R) (BM susceptible but ET non-susceptible) results are shown in the table. False-S results were low and less common for DAP than TEI or VAN. False-R was higher for DAP but most SA, CNS or Str had ET MIC of 1.5 or 2 mg/L (just above the DAP breakpoint of 1 mg/L). Efm was the most problematical for all agents, especially TEI.

Conclusion: 

ET can be relied upon to accurately ascertain susceptibility to DAP with high categorical agreement (>94%) and a very low false-S rate, this being a bigger problem than false-R.

Session Details

Date: 01/08/2007
Time: 00:00-00:00
Session name: XXIst ISTH Congress
Subject:
Location: Oxford, UK
Presentation type:
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