title: Does in vitro susceptibility to rifabutin and ethambutol predict the response to treatment of Mycobacterium avium complex bacteremia with rifabutin, ethambutol, and clarithromycin? Canadian HIV Trials Network Protocol 010 Study Group.
abstract: The in vitro susceptibilities of baseline Mycobacterium avium complex (MAC) blood isolates from 86 patients with AIDS who were treated with clarithromycin, ethambutol, and rifabutin were determined to examine whether these results predict bacteriologic response to treatment. No patient received prior prophylaxis with clarithromycin or azithromycin. Minimum inhibitory concentrations (MICs) of clarithromycin for all isolates were < or = 2 micrograms/mL. The median MIC of rifabutin was between 0.25 and 0.5 microgram/mL, and all isolates were susceptible to < or = 2 micrograms of rifabutin/mL. The median MIC of ethambutol was 4 micrograms/mL, and the MIC90 was 8 micrograms/mL. There was no correlation between ethambutol susceptibility and subsequent bacteriologic clearance. At all time points through week 12, bacteriologic clearance occurred more frequently in patients with isolates for which MICs of rifabutin were lower, but this difference was statistically significant only at week 2. Susceptibility testing for baseline MAC isolates from AIDS patients not previously treated with clarithromycin or azithromycin does not appear to be useful in guiding therapy.
authors.affiliation: Department of Medicine, University of Alberta, Edmonton, Canada.
authors.forename: S D
authors.initials: SD
authors.lastname: Shafran
authors.forename: J A
authors.initials: JA
authors.lastname: Talbot
authors.forename: S
authors.initials: S
authors.lastname: Chomyc
authors.forename: E
authors.initials: E
authors.lastname: Davison
authors.forename: J
authors.initials: J
authors.lastname: Singer
authors.forename: P
authors.initials: P
authors.lastname: Phillips
authors.forename: I
authors.initials: I
authors.lastname: Salit
authors.forename: S L
authors.initials: SL
authors.lastname: Walmsley
authors.forename: I W
authors.initials: IW
authors.lastname: Fong
authors.forename: M J
authors.initials: MJ
authors.lastname: Gill
authors.forename: A R
authors.initials: AR
authors.lastname: Rachlis
authors.forename: R G
authors.initials: RG
authors.lastname: Lalonde
mesh_terms: D017088:AIDS-Related Opportunistic Infections / Q000188:drug therapy* / Q000382:microbiology; D016470:Bacteremia / Q000188:drug therapy* / Q000382:microbiology; D017291:Clarithromycin / Q000627:therapeutic use*; D004359:Drug Therapy, Combination / Q000494:pharmacology / Q000627:therapeutic use*; D004977:Ethambutol / Q000494:pharmacology / Q000627:therapeutic use*; D006801:Humans; D008826:Microbial Sensitivity Tests; D015269:Mycobacterium avium Complex / Q000187:drug effects* / Q000302:isolation & purification; D015270:Mycobacterium avium-intracellulare Infection / Q000188:drug therapy* / Q000382:microbiology; D011237:Predictive Value of Tests; D017828:Rifabutin / Q000494:pharmacology / Q000627:therapeutic use*
chemical_list: D017828:Rifabutin; D004977:Ethambutol; D017291:Clarithromycin