Mycobacterium avium strains resistant to clarithromycin and azithromycin.
Mycobacterium avium strains susceptible to clarithromycin and azithromycin contain mutants resistant to these macrolides with a frequency of 1.1 x 10(-10) to 1.2 x 10(-6). Cross-resistance between clarithromycin and azithromycin was demonstrated with mutants selected in the laboratory as well as with resistant strains isolated from patients. The susceptibility-resistance patterns of the macrolide-resistant strains with drugs other than macrolides were the same as those of the original susceptible strains. The emergence of clarithromycin resistance in patients was a result of multiplication of the preexisting resistant mutants that survived the elimination of bacteria during the initial period of treatment and was an exclusive cause of the relapse of bacteremia.
Heifets
L
L
National Jewish Center for Immunology, and Respiratory Medicine, University of Colorado Health Sciences Center, Denver.
Mor
N
N
Vanderkolk
J
J
D017963:Azithromycin / Q000494:pharmacology*; D017291:Clarithromycin / Q000494:pharmacology*; D004352:Drug Resistance, Microbial; D006801:Humans; D008826:Microbial Sensitivity Tests; D015269:Mycobacterium avium Complex / Q000187:drug effects* / Q000378:metabolism; D015270:Mycobacterium avium-intracellulare Infection / Q000188:drug therapy / Q000382:microbiology
D017963:Azithromycin; D017291:Clarithromycin