Effect of Medium Age and Supplementation with the Biocatalytic Oxygen-Reducing Reagent Oxyrase on In Vitro Activities of Tigecycline against Recent Clinical Isolates

Petersen, Peter J.; Bradford, Patricia A.

doi:10.1128/aac.49.9.3910-3918.2005

Cited by 40 publications

(24 citation statements)

References 12 publications

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“…Broth microdilution was carried out according to the CLSI guidelines for tigecycline (7). Specifically, in light of the demonstrated oxygen sensitivity of tigecycline (3,17), MHB used for MIC determinations was prepared "fresh" (Ͻ12 h old at the time of use). Microdilution plates were prepared on the day of use, and the freshly prepared tigecycline stock solution was serially diluted in fresh MHB to provide a range of 15 twofold doubling dilutions (0.016 to 256 g/ml) to match the Etest concentration gradient range.…”

Section: Methodsmentioning

confidence: 99%

Validation and Reproducibility Assessment of Tigecycline MIC Determinations by Etest

Bolmström¹,

Karlsson²,

Engelhardt³

et al. 2007

J Clin Microbiol

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A multicenter study was conducted to validate Etest tigecycline compared to the Clinical Laboratory Standards Institute reference broth microdilution and agar dilution methodologies. A large collection of gram-negative (n ‫؍‬ 266) and gram-positive (n ‫؍‬ 162) aerobic bacteria, a collection of anaerobes (n ‫؍‬ 385), and selected collections of nonpneumococcal streptococci (n ‫؍‬ 369), Streptococcus pneumoniae (n ‫؍‬ 372), and Haemophilus influenzae (n ‫؍‬ 372) were tested. Strains with reduced susceptibility to tigecycline were used with all test methods. The Etest showed excellent inter-and intralaboratory reproducibility for all organism groups tested regardless of the test methodology. The essential agreement values with the reference method (؎1 dilution) were >99% for the collection of gram-negative and gram-positive aerobes; >98% for the S. pneumoniae, H. influenzae, and anaerobe collections; and 100% for the group of nonpneumococcal streptococci. These results validate the performance accuracy and utility of Etest tigecycline and verify the reproducibility of this convenient predefined gradient methodology for tigecycline susceptibility determination.

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Section: Methodsmentioning

confidence: 99%

Validation and Reproducibility Assessment of Tigecycline MIC Determinations by Etest

Bolmström¹,

Karlsson²,

Engelhardt³

et al. 2007

J Clin Microbiol

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“…In addition, it has been shown to be active against microorganisms known to be resistant to other classes of antimicrobial agents (1,11,12,19,20,22). Recent studies have found that the age of the broth medium used for in vitro susceptibility testing can affect the MICs of tigecycline by as much as two to eightfold (5,21). Susceptibility tests performed with medium which was Յ12 h old at the time of testing produced MICs which were substantially lower than those observed with medium that had been aged for various periods of time up to 1 month.…”

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confidence: 99%

Comparative In Vitro Antimicrobial Activity of Tigecycline, a New Glycylcycline Compound, in Freshly Prepared Medium and Quality Control

Brown

Traczewski

2007

J Clin Microbiol

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The in vitro spectra of activity of tigecycline and tetracycline were determined for 2,490 bacterial isolates representing 50 different species or phenotypic groups. All isolates were tested simultaneously by broth microdilution using freshly prepared Mueller-Hinton broth and by disk diffusion. Portions of these data were submitted to the Food and Drug Administration (FDA) in support of the sponsor's application for new drug approval. In a separate study, MIC and disk diffusion quality control ranges were determined. The tigecycline MICs at which 50%/90% of bacteria were inhibited were (in g/ml) as follows: for Streptococcus spp., 0.06/0.12; for Moraxella catarrhalis, 0.06/0.12; for Staphylococcus spp., 0.12/0.25; for Enterococcus spp., 0.12/0.25; for Listeria monocytogenes, 0.12/0.12; for Neisseria meningitidis, 0.12/0.25; for Haemophilus spp., 0.25/0.5; for Enterobacteriaceae, 0.05/2.0; for non-Enterobacteriaceae, 0.5/8.0. Tigecycline was consistently more potent than tetracycline against all species studied. The data from this study confirm the FDA-approved MIC and disk diffusion breakpoints for tigecycline for Streptococcus spp. other than Streptococcus pneumoniae, enterococci, and Enterobacteriaceae. Provisional breakpoints for Haemophilus spp. and S. pneumoniae are proposed based on the data from this study. The following MIC and/or disk diffusion quality control ranges are proposed: Staphylococcus aureus ATCC 29213, 0.03 to 0.25 g/ml; S. aureus ATCC 25923, 20 to 25 mm; Escherichia coli ATCC 25922, 0.03 to 0.25 g/ml and 20 to 27 mm; Pseudomonas aeruginosa ATCC 27853, 9 to 13 mm, Enterococcus faecalis ATCC 29212, 0.03 to 0.12 g/ml; S. pneumoniae ATCC 49619, 0.015 to 0.12 g/ml and 23 to 29 mm; Haemophilus influenzae ATCC 49247, 0.06 to 0.5 g/ml and 23 to 31 mm; and Neisseria gonorrhoeae ATCC 49226, 30 to 40 mm.Tigecycline (formerly GAR-936) is a new glycylcycline (24) compound with a broad spectrum of antibacterial activity (2-4, 8, 10, 13, 14, 23). In addition, it has been shown to be active against microorganisms known to be resistant to other classes of antimicrobial agents (1,11,12,19,20,22). Recent studies have found that the age of the broth medium used for in vitro susceptibility testing can affect the MICs of tigecycline by as much as two to eightfold (5, 21). Susceptibility tests performed with medium which was Յ12 h old at the time of testing produced MICs which were substantially lower than those observed with medium that had been aged for various periods of time up to 1 month. The effects of medium aging could be counteracted by the addition of Oxyrase, a biocatalytic oxygenreducing reagent, to the susceptibility testing medium. Further testing revealed that dissolving tigecycline in aged medium resulted in the formation of an oxidized tigecycline product which had decreased antibacterial activity (5). Once the MIC trays were frozen, the oxidation of the drug was minimal. MIC trays which were prepared using freshly prepared medium and stored at Ϫ20°C for several weeks produced results which were...

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“…It can be oxidized when added to a broth medium that has been oxygenated during storage (13) or when tigecycline-containing broth is stored before inoculation. This can be solved using freshly autoclaved broth or recently prepared solid media (2) and is expected to be avoided in the disk diffusion or gradient diffusion (Etest) assays.…”

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confidence: 99%

High Concentrations of Manganese in Mueller-Hinton Agar Increase MICs of Tigecycline Determined by Etest

et al. 2009

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MICs of tigecycline determined by Etest were 4 to 12 times (three ATCC strains) and 2 to 8 times (50 clinical isolates) higher in Mueller-Hinton agar from Merck than in Mueller-Hinton agar from either Oxoid or Difco. This was related to a much higher concentration of manganese in the medium from Merck.Tigecycline is the first glycylcycline approved for clinical use (16). It can be oxidized when added to a broth medium that has been oxygenated during storage (13) or when tigecycline-containing broth is stored before inoculation. This can be solved using freshly autoclaved broth or recently prepared solid media (2) and is expected to be avoided in the disk diffusion or gradient diffusion (Etest) assays.During a nation-wide study in Spain on the activity of tigecycline against clinical isolates using Etest strips (AB Biodisk, Solna, Sweden), the results in our center were up to 16 to 20 times higher than those obtained in other centers (A. Pérez, Wyeth Farma S.A., Spain, personal communication). After excluding the possibility that some technical error occurred in our laboratory, we hypothesized that these results could be related to differences in the composition of the Mueller-Hinton agar used in different laboratories, as the commercial source for this medium in our center (Merck) was different from that in many other laboratories in Spain.In this study, the activity of tigecycline determined with Etest strips on two different lots of commercially available MuellerHinton agar from Oxoid (Basingstoke, Hampshire, England; lots 418599 and 456733), Difco (Difco Mueller-Hinton agar [BD, Sparks, MD]; lots 6093187 and 6177851), and Merck (Darmstadt, Germany; lots VL379337507 and VL546637607) was evaluated. We also determined the effect that differences in the concentrations of ions of the evaluated Mueller-Hinton agars may have on the in vitro activity of tigecycline.In a preliminary study, five clinical isolates (selected among those we already tested in the multicenter study in Spain) and four reference strains, namely, Escherichia coli ATTC 25922, Pseudomonas aeruginosa ATCC 27953, Staphylococcus aureus 29213, and Enterococcus faecalis 29212, were evaluated. MICs of tigecycline for these two groups of organisms were consistently 4 to 12 times higher in the medium from Merck than in the medium from Difco or Oxoid, except for the P. aeruginosa ATCC strain (MICs of 64 to 128 g/ml in the three media) (data not shown).In a second phase, MICs of tigecycline for 50 clinical isolates (one per patient; clonally unrelated as assessed by repetitive extragenic palindromic PCR and/or pulsed-field gel electrophoresis) were determined in duplicate experiments on different days. Extended-spectrum ␤-lactamase (ESBL) production was confirmed by disk diffusion (4). Resistance to methicillin in S. aureus and to vancomycin in Enterococcus faecium was confirmed by PCR detection of the mecA (9) and vanA (12) genes, respectively. MICs of tigecycline were also determined by microdilution, according to CLSI guidelines (5) using fresh Mueller...

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Effect of Medium Age and Supplementation with the Biocatalytic Oxygen-Reducing Reagent Oxyrase on In Vitro Activities of Tigecycline against Recent Clinical Isolates

Cited by 40 publications

References 12 publications

Validation and Reproducibility Assessment of Tigecycline MIC Determinations by Etest

Validation and Reproducibility Assessment of Tigecycline MIC Determinations by Etest

Comparative In Vitro Antimicrobial Activity of Tigecycline, a New Glycylcycline Compound, in Freshly Prepared Medium and Quality Control

High Concentrations of Manganese in Mueller-Hinton Agar Increase MICs of Tigecycline Determined by Etest

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