Factors influencing broth microdilution antimicrobial susceptibility test results for dalbavancin, a new glycopeptide agent.
Performance of antimicrobial susceptibility tests with new agents requires careful consideration of the properties of the antimicrobial to ensure that the tests are standardized, reproducible, and reflect the true potency of the drug. Dalbavancin is a new glycopeptide with potent activity against gram-positive bacterial species. The investigations described here demonstrated that methodologic modifications of procedures are necessary to ensure consistent test results, both for quality control and for routine testing of clinical isolates. Dimethyl sulfoxide is the preferred primary solvent. The addition of 0.002% polysorbate-80 (a surfactant) to dalbavancin-containing wells in the reference broth microdilution assay resulted in consistent and reproducible MIC results for three quality control strains: Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212, and Streptococcus pneumoniae ATCC 49619. The same degree of consistency was observed among clinical isolates of gram-positive bacterial species tested in several clinical laboratories. These results indicate that the addition of 0.002% (final concentration) of the surfactant in broth microdilution tests produces optimal dalbavancin MICs required for accurate and reproducible clinical laboratory tests, without untoward influences of substrate binding or media constituents.
Medical Microbiology, University of Alberta Hospital, WMC 283.08, 8440 112 St., Edmonton, Alberta T6G 2J2, Canada. robert.rennie@capitalhealth.ca
Robert P
RP
Rennie
Laura
L
Koeth
Ronald N
RN
Jones
Thomas R
TR
Fritsche
Cindy C
CC
Knapp
Scott B
SB
Killian
Beth P
BP
Goldstein
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods*; D013211:Staphylococcus aureus / Q000187:drug effects; D013291:Streptococcus / Q000187:drug effects; D017334:Teicoplanin / Q000031:analogs & derivatives* / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D017334:Teicoplanin; C469289:dalbavancin