1The Jones Group/JMI Laboratories, North Liberty, IA; 2Tufts University School of Medicine, Boston, MA, USA
Received 25 October 2001; returned 21 January 2002; revised 21 February 2001; accepted 26 February 2002.
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Abstract |
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Introduction |
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Materials and methods |
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The comparator drugs tested were obtained from the United States manufacturers and AZD2563 was provided by AstraZeneca (Macclesfield, UK). The antimicrobials included: linezolid,6 quinupristindalfopristin, vancomycin, erythromycin, clindamycin, gentamicin, levofloxacin and penicillin.
Bacterial isolates
The 525 strains tested were from various North American surveillance collections processed in the last 12 months by the JMI Laboratories (North Liberty, IA, USA). These strains included: viridans group streptococci (259 strains) and ß-haemolytic streptococci (five serogroups, 266 strains). Each strain was identified by two or more laboratories and represented isolates derived from recent clinical cases. For 126 viridans group streptococci, high confidence identification (85%) to species level could not be made; these strains were classified as viridans group, NOS (not otherwise speciated). The remaining strains were identified as follows: Streptococcus anginosis (four strains), Streptococcus constellatus (four strains), Streptococcus equinus (one strain), Streptococcus equisimilus (one strain), Streptococcus gordonii (one strain), Streptococcus intermedius (14 strains), Streptococcus milleri (17 strains), Streptococcus mitis (48 strains), Streptococcus mutans (one strain), Streptococcus oralis (15 strains), Streptococcus salvarius (six strains), Streptococcus sanguis (20 strains), Streptococcus uberis (one strain), and ß-haemolytic streptococci from groups A (112 strains), B (132 strains), C (11 strains), F (one strain) and G (10 strains). All viridans group strains were isolated from bloodstream infections, and the ß-haemolytic isolates came from cultures of blood, wounds and the upper airway.
Susceptibility testing
All strains were tested by the NCCLS broth microdilution method.9 Broth microdilution trays were prepared in frozen form by Trek Diagnostics (Westlake, OH, USA) and stored at 80°C until used. Antimicrobials were diluted in MuellerHinton broth with 5% lysed horse blood and the final inoculum was 5 x 105 cfu/mL, confirmed by regular colony counts. Quality control (QC) strains included fastidious (S. pneumoniae ATCC 49619) and rapidly growing species (Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212). All QC results were within control ranges published by the NCCLS10 or product manufacturer (AstraZeneca).
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Results |
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When analysing all 525 streptococcal isolates tested, AZD2563 and linezolid had nearly identical MIC ranges (0.062 mg/L of AZD2563 compared with 0.122 mg/L of linezolid) as well as MIC50 and MIC90 results. However, Figure 1 demonstrates that AZD2563 had a slight potency advantage for some streptococcal strains when compared with linezolid.
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Discussion |
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Acknowledgements |
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Footnotes |
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References |
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2
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6 . Diekema, D. J. & Jones, R. N. (2001). Oxazolidinone antibiotics. Lancet 358, 197582.[ISI][Medline]
7 . Johnson, A. P., Warner, M., Parsons, T. & Livermore, D. M. (2001). In vitro activity of a novel oxazolidinone, AZD2563, against Gram-positive cocci, including diverse multi-resistant isolates. In Program and Abstracts of the Forty-first Interscience Conference on Antimicrobial Agents and Chemotherapy, Chicago, IL, 2001. Abstract F-1026, p. 223. American Society for Microbiology, Washington, DC.
8 . Turner, P. J., Wookey, A., Greenhalgh, J. M., Eastwood, M. & Clarke, J. (2001). Investigations into the antibacterial spectrum of the new oxazolidinone, AZD2563, against recent clinical isolates from North America and Europe. In Program and Abstracts of the Forty-first Interscience Conference on Antimicrobial Agents and Chemotherapy, Chicago, IL, 2001. Abstract F-1024, p. 222. American Society for Microbiology, Washington, DC.
9 . National Committee for Clinical Laboratory Standards. (2000). Performance Standard for Antimicrobial Susceptibility TestingSeventh Edition: Approved Standard M2-A7. NCCLS, Wayne, PA.
10 . National Committee for Clinical Laboratory Standards. (2002). Performance Standard for Antimicrobial Susceptibility Testing. Document M100-S12. NCCLS, Wayne, PA.
11 . Craig, W. A. & Andes, D. R. (2001). Pharmacodynamic characteristics of AZD2563, the new oxazolidinone, in a murine thigh-infection model. In Program and Abstracts of the Forty-first Interscience Conference on Antimicrobial Agents and Chemotherapy, Chicago, IL, 2001. Abstract 1037, p. 226. American Society for Microbiology, Washington, DC.