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J Antimicrob Chemother. 2009 Aug;64(2):310-6. doi: 10.1093/jac/dkp184. Epub 2009 May 20.

Comparison of three methods for susceptibility testing of Mycobacterium avium subsp. paratuberculosis to 11 antimicrobial drugs.

Author information

1
Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Drive, Madison, WI 53706-110, USA.

Abstract

OBJECTIVES:

To evaluate the BACTEC(TM) MGIT(TM) 960/MGIT Para TB (MGIT) system for drug susceptibility testing of Mycobacterium avium subsp. paratuberculosis (MAP), a pathogen implicated in some forms of Crohn's disease.

METHODS:

MICs of 11 drugs for 10 MAP strains were determined using the MGIT system, the BACTEC(TM)460TB system (BACTEC) and conventional agar dilution methods.

RESULTS:

MICs determined by MGIT methods showed 80%-100% agreement (+/-1 log(2) dilution) with those determined by the BACTEC and agar dilution methods for ciprofloxacin, levofloxacin, azithromycin and clofazimine. The MGIT and BACTEC methods showed 70%, 80% and 90% agreement (+/-1 log(2) dilution) for MICs of ethambutol, rifabutin and rifampicin; agreement for all drugs increased to 100% at 2 log(2) dilution differences. For clarithromycin, the MGIT method had greater agreement with the agar dilution method (70% at the same dilution) than the BACTEC method (60% at +/-1 log(2) dilution); agreement increased to 100% at +/-2 log(2) dilutions in both cases. The MGIT and agar dilution methods agreed 60% and 100% for amikacin MICs at +/-1 log(2) dilution and +/-2 log(2) dilutions, respectively. By all methods MICs were higher than achievable serum concentrations for isoniazid and dapsone. There was 100% agreement between all three methods for azithromycin, clarithromycin and ciprofloxacin, and 80% agreement for rifampicin using published MIC thresholds available for M. avium complex strains.

CONCLUSIONS:

This study shows that the MGIT system can be used for rapid and reliable drug susceptibility testing of MAP.

PMID:
19457932
DOI:
10.1093/jac/dkp184
[Indexed for MEDLINE]

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