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Impact of carbon dioxide on the susceptibility of key respiratory tract pathogens to telithromycin and azithromycin.
J Antimicrob Chemother. 2005 Jul; 56(1):224-7.JA

Abstract

OBJECTIVES

To determine the quantitative differences in telithromycin and azithromycin MIC values against Streptococcus pneumoniae, Haemophilus influenzae and Streptococcus pyogenes obtained using two recommended and commonly used methodologies: CLSI reference standard broth microdilution in ambient air and Etest((R)) concentration gradient in CO(2).

METHODS

Four hundred clinical isolates (S. pneumoniae, n = 200; H. influenzae, n = 100; S. pyogenes, n = 100) were evaluated in seven independent laboratories. Telithromycin and azithromycin MICs were determined using CLSI broth microdilution panels incubated in ambient air and Etest strips incubated in CO(2). Standard quality control reference strains-S. pneumoniae ATCC 49619 (n = 10) and H. influenzae ATCC 49247 (n = 10)-were also tested.

RESULTS

Telithromycin and azithromycin Etest MICs in CO(2) were elevated for all organisms when compared with values obtained using broth microdilution in ambient air. Telithromycin geometric mean MIC values increased in CO(2) by 2.05, 1.00 and 1.78 log(2) dilutions for S. pneumoniae, H. influenzae and S. pyogenes, respectively. The corresponding values for azithromycin were 2.54, 1.21 and 3.0 log(2) dilutions, respectively.

CONCLUSIONS

Telithromycin MICs measured using Etest in CO(2) are consistently elevated compared with those generated by CLSI broth microdilution measured in ambient air. These findings indicate that Etest should not be routinely used for the determination of telithromycin MICs against S. pneumoniae, H. influenzae and S. pyogenes, unless appropriate corrective factors are applied before reporting MICs or applying interpretive susceptibilities. Based on results from this study, Etest MIC breakpoints and quality control ranges are proposed.

Authors+Show Affiliations

Laboratories International for Microbiology Studies, Inc., Schaumburg, IL 60173-3817, USA. sbouchillon@ihmaninc.comNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

15890718

Citation

Bouchillon, Sam K., et al. "Impact of Carbon Dioxide On the Susceptibility of Key Respiratory Tract Pathogens to Telithromycin and Azithromycin." The Journal of Antimicrobial Chemotherapy, vol. 56, no. 1, 2005, pp. 224-7.
Bouchillon SK, Johnson JL, Hoban DJ, et al. Impact of carbon dioxide on the susceptibility of key respiratory tract pathogens to telithromycin and azithromycin. J Antimicrob Chemother. 2005;56(1):224-7.
Bouchillon, S. K., Johnson, J. L., Hoban, D. J., Stevens, T. M., & Johnson, B. M. (2005). Impact of carbon dioxide on the susceptibility of key respiratory tract pathogens to telithromycin and azithromycin. The Journal of Antimicrobial Chemotherapy, 56(1), 224-7.
Bouchillon SK, et al. Impact of Carbon Dioxide On the Susceptibility of Key Respiratory Tract Pathogens to Telithromycin and Azithromycin. J Antimicrob Chemother. 2005;56(1):224-7. PubMed PMID: 15890718.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Impact of carbon dioxide on the susceptibility of key respiratory tract pathogens to telithromycin and azithromycin. AU - Bouchillon,Sam K, AU - Johnson,Jack L, AU - Hoban,Daryl J, AU - Stevens,Tim M, AU - Johnson,Brian M, Y1 - 2005/05/12/ PY - 2005/5/14/pubmed PY - 2005/9/2/medline PY - 2005/5/14/entrez SP - 224 EP - 7 JF - The Journal of antimicrobial chemotherapy JO - J Antimicrob Chemother VL - 56 IS - 1 N2 - OBJECTIVES: To determine the quantitative differences in telithromycin and azithromycin MIC values against Streptococcus pneumoniae, Haemophilus influenzae and Streptococcus pyogenes obtained using two recommended and commonly used methodologies: CLSI reference standard broth microdilution in ambient air and Etest((R)) concentration gradient in CO(2). METHODS: Four hundred clinical isolates (S. pneumoniae, n = 200; H. influenzae, n = 100; S. pyogenes, n = 100) were evaluated in seven independent laboratories. Telithromycin and azithromycin MICs were determined using CLSI broth microdilution panels incubated in ambient air and Etest strips incubated in CO(2). Standard quality control reference strains-S. pneumoniae ATCC 49619 (n = 10) and H. influenzae ATCC 49247 (n = 10)-were also tested. RESULTS: Telithromycin and azithromycin Etest MICs in CO(2) were elevated for all organisms when compared with values obtained using broth microdilution in ambient air. Telithromycin geometric mean MIC values increased in CO(2) by 2.05, 1.00 and 1.78 log(2) dilutions for S. pneumoniae, H. influenzae and S. pyogenes, respectively. The corresponding values for azithromycin were 2.54, 1.21 and 3.0 log(2) dilutions, respectively. CONCLUSIONS: Telithromycin MICs measured using Etest in CO(2) are consistently elevated compared with those generated by CLSI broth microdilution measured in ambient air. These findings indicate that Etest should not be routinely used for the determination of telithromycin MICs against S. pneumoniae, H. influenzae and S. pyogenes, unless appropriate corrective factors are applied before reporting MICs or applying interpretive susceptibilities. Based on results from this study, Etest MIC breakpoints and quality control ranges are proposed. SN - 0305-7453 UR - https://www.unboundmedicine.com/medline/citation/15890718/Impact_of_carbon_dioxide_on_the_susceptibility_of_key_respiratory_tract_pathogens_to_telithromycin_and_azithromycin_ L2 - https://academic.oup.com/jac/article-lookup/doi/10.1093/jac/dki156 DB - PRIME DP - Unbound Medicine ER -