title: Evaluation of a disk diffusion method for determining susceptibility of Mycobacterium avium complex to clarithromycin.
abstract: We evaluated an agar disk diffusion method for determining the susceptibility of Mycobacterium avium complex to clarithromycin. Isolates were inoculated onto the surface of a Middlebrook 7H11 plate, followed by the application of a 15-microgram clarithromycin disk. Zone sizes were read after 5-7 days of incubation. Zone sizes had a bimodal distribution; 40 isolates (10%) had no zone of inhibition, whereas the zone sizes for the remaining isolates ranged from 11 to 60 mm. Most isolates (37/40) having no zone of inhibition came from patients who had been treated previously with clarithromycin. Fifty-one isolates were also tested for clarithromycin susceptibility using a microdilution broth method. Defining susceptibility as a zone size of > 10 mm, disk diffusion test results agreed with the results by the microdilution broth method for 50 of 51 (98%) isolates tested by both methods. Agar disk diffusion is a promising method for the determination of clarithromycin susceptibility testing for M. avium complex.
authors.affiliation: Mycobacteriology Laboratory, Denver Health and Hospitals, Colorado, USA.
authors.forename: E
authors.initials: E
authors.lastname: Jarboe
authors.forename: B L
authors.initials: BL
authors.lastname: Stone
authors.forename: W J
authors.initials: WJ
authors.lastname: Burman
authors.forename: R J
authors.initials: RJ
authors.lastname: Wallace
authors.forename: B A
authors.initials: BA
authors.lastname: Brown
authors.forename: R R
authors.initials: RR
authors.lastname: Reves
authors.forename: M L
authors.initials: ML
authors.lastname: Wilson
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D017291:Clarithromycin / Q000494:pharmacology*; D004352:Drug Resistance, Microbial; D006801:Humans; D008826:Microbial Sensitivity Tests; D015269:Mycobacterium avium Complex / Q000187:drug effects* / Q000254:growth & development / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D017291:Clarithromycin