title: Telavancin activity when tested by a revised susceptibility testing method against uncommonly isolated Gram-positive pathogens responsible for documented infections in hospitals worldwide (2011-2013).
abstract: The broth microdilution method for telavancin susceptibility testing was revised and now utilises DMSO as solvent for stock solution preparation and diluent for stock solution dilution, following CLSI guidelines for water-insoluble agents. The revised method also incorporates polysorbate 80 in the test medium to mitigate drug binding to plastics. This revised methodology provides more accurate and reproducible MIC determinations, which results in values lower than the previously established method. This study was conducted to re-establish telavancin potencies and susceptibility profiles (using updated interpretive criteria) against a collection of uncommon clinical pathogens (3821 isolates). Telavancin showed MIC50values of 0.06mg/L against tested staphylococcal species (MIC50/90, 0.03/0.06mg/L; 98.1-100.0% susceptible), with lower results for Staphylococcus hominis (MIC50, ≤0.015mg/L), Staphylococcus lugdunensis (MIC50, ≤0.015mg/L) and Staphylococcus simulans (MIC50, 0.03mg/L). Vancomycin (MIC50, 1mg/L), daptomycin (MIC50, 0.12-1mg/L) and linezolid (MIC50, 0.25-1mg/L) had MIC50results at least four-fold higher than telavancin against CoNS. Streptococci (99.2-100.0% susceptible) displayed telavancin MIC50values of ≤0.015-0.03mg/L. Vancomycin (MIC50, 0.25-0.5mg/L) and linezolid (MIC50, 0.5-1mg/L) had higher MIC50results against streptococci, whilst daptomycin MIC50values varied from ≤0.06mg/L to 0.5mg/L. Micrococcus, Listeria and Corynebacterium spp. were inhibited by telavancin at ≤0.015, ≤0.03 and ≤0.06mg/L, respectively. Telavancin exhibited potent in vitro activity against this collection, greater than comparators (daptomycin, linezolid, vancomycin). This study provides new baseline MIC results for telavancin and confirms the spectrum and potency of telavancin against less commonly encountered Gram-positive species.
authors.affiliation: JMI Laboratories, North Liberty, IA, United States. Electronic address: rodrigo-mendes@jmilabs.com.
authors.forename: Rodrigo E
authors.initials: RE
authors.lastname: Mendes
authors.affiliation: JMI Laboratories, North Liberty, IA, United States.
authors.forename: Helio S
authors.initials: HS
authors.lastname: Sader
authors.affiliation: JMI Laboratories, North Liberty, IA, United States.
authors.forename: Robert K
authors.initials: RK
authors.lastname: Flamm
authors.affiliation: JMI Laboratories, North Liberty, IA, United States.
authors.forename: David J
authors.initials: DJ
authors.lastname: Farrell
authors.affiliation: JMI Laboratories, North Liberty, IA, United States.
authors.forename: Ronald N
authors.initials: RN
authors.lastname: Jones
keywords: Broth microdilution; Lipoglycopeptide; Polysorbate 80; Susceptibility