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The reference broth microdilution BMD antimicrobial susceptibility testing method for telavancin was revised to include dimethyl sulfoxide DMSO as a solvent and diluent for frozen-form panel preparation, following the CLSI recommendations for water-insoluble agents. Polysorbate 80 P was also added to the test medium to minimize vlsi drug losses associated with binding to plastic surfaces. Four s2 sixty-two Gram-positive isolates, including a challenge set of organisms with reduced susceptibilities to comparator agents, were selected and tested using the revised method for telavancin, and the MIC results were compared with those tested by the previously established method and several Sensititre dry-form BMD panel formulations.
The revised method provided MIC results 2- to clzi lower than the previous method when tested against staphylococci and enterococci, resulting in MIC 50 values cksi 0. Less-significant MIC decreases 1 to 2 log 2 dilution steps were observed when testing streptococci in broth supplemented with blood, which showed similar MIC 50 values for both methods.
However, Streptococcus pneumoniae had MIC 50 results of 0. The revised BMD method provides lower Clsj results for telavancin, especially when tested against staphylococci and enterococci. This is secondary to the use of DMSO for panel production and the presence of P, which ensure the proper telavancin testing concentration and result in a more accurate MIC determination.
Moreover, earlier studies where the previous method was applied underestimated the in vitro drug potency.
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Telavancin is a lipoglycopeptide antibiotic with potent in vitro bactericidal activity when tested against Gram-positive bacteria, including methicillin-susceptible Staphylococcus aureus MSSAmethicillin-resistant S.
During the development of dalbavancin, also a lipoglycopeptide, the use of polysorbate 80 P 0. Subsequent investigations for oritavancin another lipoglycopeptide demonstrated that the addition of P to MIC testing broth was also necessary for test performance reliability via minimizing the drug binding to plastic well panels 5similar to dalbavancin. The antimicrobial susceptibility testing for these lipoglycopeptide agents was revised 67and updated quality control QC ranges for dalbavancin and oritavancin were established and published by the Clinical and Laboratory Standards Institute CLSIin MS24 and previous documents 8.
Surfactants, such as P, act as wetting agents and are commonly used in commercially prepared antimicrobial agent susceptibility testing panels or as part of the inoculum for broth microdilution assays to aid in the homogenous dispersal of reagents or to ensure their quantitative recovery from solution 45.
Further investigations proposed the use of dimethyl sulfoxide DMSO as the clxi for stock solution preparation, as well as a stock solution diluent for panel preparation. In addition, P was incorporated into the test medium. These changes were shown to improve drug solubility during panel preparation DMSO and drug availability in the well plastic plates Presulting in a more accurate in vitro assessment of telavancin MIC determinations data on file; Theravance, Inc.
Initial studies using this revised method observed that the MIC 50 results for telavancin were 4- to 8-fold lower than those obtained by the previous applied method use of DMSO and water as solvent and diluent for panel preparation, respectively, and no P supplementation when tested against staphylococci and enterococci, but minimal differences were observed clso testing streptococci data on file; JMI Laboratories.
The revised method and subsequent differences in MIC results prompted the reestablishment of QC ranges for telavancin 9 and cllsi breakpoints 3. The revised method, along with QC ranges and updated breakpoints, was approved by the Food and Drug Administration FDA and incorporated into the labeling supplement for the product Vibativ telavancin 3.
The purpose of this study was to fully evaluate telavancin MIC results when using the revised BMD method compared with those obtained by the previous CLSI method when tested against a larger collection of clinically relevant strains.
In addition, the telavancin MIC results obtained with the revised method were compared with several candidate dry-form formulation panels. A total of clinical isolates were included in this study.
Initially, Gram-positive clinical strains collected during previous worldwide surveillance programs These strains originated predominantly in U. Second, a challenge set of organisms 56 strains displaying decreased antimicrobial susceptibilities to several key comparator agents were selected and included in this study, as follows: Some of m10 isolates included in this set 22 strains were provided by the Network on Antimicrobial Resistance in S.
Frozen-form panels produced according to the previously established susceptibility testing method were manufactured, following the previous CLSI recommendations MS23 Several Sensititre dry-form broth microdilution panel candidate formulations eight were manufactured and tested simultaneously with the previous and revised frozen-form panels. Cllsi was supplemented with 2. All telavancin MIC QC values obtained by frozen-form panels prepared according to the previous and revised methods were within the ranges published in the MS23 and MS24 documents, respectively 38— Telavancin MIC values obtained by s223 revised method were considered reference results for these analyses.
MIC result variations and summary of essential agreement rates between previously established broth microdilution method and revised reference method for telavancin. In vitro MIC results for telavancin when tested against Gram-positive isolates using previously established broth microdilution method and revised reference method.
The previous method generated results against all E. Differences in MIC results between frozen-form BMD methods were less significant for the streptococci, where the majority of MIC values obtained by the previous method were only 1 doubling dilution step higher than those obtained by the revised method Table 1.
The previous method produced most MIC results against S.
Among candidate dry-form panels tested, all had EA rates above the minimal acceptable target i. MIC result variations and summary of essential agreement rates between dry-form broth microdilution formulation panel Sensititre and revised reference method for telavancin. As previously observed with dalbavancin 4 and oritavancin 5the data presented here, using a large collection of clinically relevant strains, shows that the revised BMD method containing the addition of P common to all three lipoglycopeptides provides lower MIC results than those obtained by the cllsi method, especially when tested against staphylococci and enterococci.
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In contrast, when tested against streptococci, the impact of the revised method on the telavancin MIC results was less pronounced, which was similar to those observed for the other lipoglycopeptides 45. These results suggest that i P is necessary for a more accurate MIC determination for telavancin and previous studies underestimated the drug’s in vitro potency due to drug loss because of binding to plastic surfaces 1213— 15 and ii similar to dalbavancin and oritavancin, presence of LHB provides an effect similar to that of P Similar experiments were performed for telavancin, and similar results were obtained data on file; Theravance, Inc.
Also noteworthy were the 4- to 8-fold-lower telavancin MIC results obtained against S.
During the development of this revised method, previous telavancin MIC determinations obtained when P was added only at the latest step bacterial inoculation resulted in MIC values against S. These results also were observed for oritavancin, indicating that the presence of P at 0. This additional evidence supports that P minimizes drug binding to plastic surfaces, rather than acting synergistically with telavancin.
Otherwise, if s233 activity were expected, results should have been similar, since the final testing concentration of P was the same for both determinations but was just introduced at a different phase of susceptibility testing 5. It is also important to mention that although this revised method provides lower MIC determinations for telavancin, the antimicrobial susceptibility profile remains similar to that established by using the previous BMD method 1213— These antimicrobial profile characteristics have been very well documented in studies performed during drug development or after regulatory approval when applying the m1000 BMD method 1213— Clxi summary, these study results demonstrate that the previous BMD method adopted by CLSI use of DMSO as a solvent and diluent for panel s32 and addition of P to the broth ensures a proper assessment of the telavancin MIC determination, especially when tested against staphylococci and enterococci.
The results presented here also m1100 a commercial dry-form formulation panel, which can be used as an z23 method for telavancin susceptibility testing in the clinical microbiology setting, along with adequate QC ranges and interpretive breakpoints 389.
Lastly, the telavancin in vitro MIC results tested against Gram-positive organisms by the revised BMD method are now comparable to those reported for other lipoglycopeptide agents i. M1000 San Francisco, CA. Jones are employees of JMI Laboratories who receive grant funds to study telavancin and were paid consultants to Theravance in connection with the development of the manuscript.
Coordination of scientific review of the draft manuscript by Ss23 and partners was conducted by Suzanne Douthwaite, an cllsi of Envision Scientific Solutions, funded by Theravance. Published ahead of print 14 July National Center for Biotechnology InformationU. Journal List Antimicrob Agents Chemother dlsi. FarrellRodrigo E. MendesPaul R.
Rhombergand Ronald N. Author information Article notes Copyright and License information Disclaimer. Address correspondence to David J. The authors have paid a fee to allow immediate free access to this article.
This article has been cited by other k100 in PMC. Abstract The reference broth microdilution BMD antimicrobial susceptibility testing method for telavancin was revised to include dimethyl sulfoxide DMSO as a solvent and diluent for frozen-form panel preparation, following the CLSI recommendations for water-insoluble agents.
TABLE 1 MIC result variations and summary of essential agreement rates clei previously established broth microdilution method and revised reference method for telavancin.
Open in a separate window. TABLE 2 In vitro MIC results for telavancin when tested against Gram-positive isolates using previously established broth microdilution method and revised reference clso. TABLE 3 MIC result variations and summary of essential agreement rates between dry-form broth microdilution formulation panel Sensititre and revised reference method for telavancin. Footnotes Published ahead of print 14 July Telavancin activity tested against a contemporary collection of Gram-positive pathogens from USA 1m00 In vitro activity of telavancin and comparator antimicrobial agents against a panel of genetically defined staphylococci.
Factors influencing broth microdilution antimicrobial susceptibility test results for dalbavancin, a new glycopeptide agent. Effect of polysorbate 80 on oritavancin binding to plastic surfaces: Initial quality control evaluations for susceptibility testing of dalbavancin BIan investigational glycopeptide with potent Gram-positive activity. Newly defined in vitro quality control ranges for oritavancin broth microdilution testing and impact of variation in testing parameters.
Clinical and Laboratory Standards Institute. Performance standards for antimicrobial susceptibility testing: Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically: Food and Drug Administration.
Guidance for industry and FDA. Class II special controls guidance document: Update on the telavancin activity tested against European staphylococcal clinical isolates Comparative surveillance study of telavancin activity against recently j100 Gram-positive clinical isolates from across the United States. In vitro activity of telavancin against recent Gram-positive clinical isolates: Surveillance of dalbavancin potency and spectrum in the United States Oritavancin activity against Staphylococcus aureus causing invasive infections in USA and European hospitals.