The relationship between the in vitro drug susceptibility of opportunist mycobacteria and their in vivo response to treatment.
METHODS
It is generally accepted that qualitative drug susceptibility tests established and validated for Mycobacterium tuberculosis are not applicable to opportunist (non-tuberculous) mycobacteria. Previous studies have shown that in vitro antimicrobial susceptibilities for opportunist mycobacteria, performed by the method of modal resistance (MR), correlate poorly with clinical response. Minimum inhibitory concentration (MIC) determination may provide better correlation with predicted clinical response than the conventional MR results.


OBJECTIVE
To determine the relationship between quantitative in vitro sensitivity results for opportunist mycobacteria and their in vivo response to treatment.


METHODS
MICs were performed radiometrically with the Bactec TB-460 system; 35 M. avium complex isolates, 29 isolates of M. malmoense and 16 isolates of M. xenopi were tested.


RESULTS
Susceptibility results were analysed in comparison with therapeutic outcome by Fisher's exact probability test. Only one significant association was found; in vitro resistance to ethambutol correlated with treatment failure for M. malmoense infections (P = 0.027). There were no other significant correlations between in vitro results and treatment outcome.


CONCLUSIONS
Prediction of treatment outcome from in vitro susceptibility tests continues to be a problem in infections with opportunist mycobacteria.
Heginbothom
M L
ML
Department of Medical Microbiology, University Hospital of Wales, Cardiff, UK. heginbothom@cardiff.ac.uk
D000995:Antitubercular Agents / Q000494:pharmacology* / Q000627:therapeutic use; D004977:Ethambutol / Q000494:pharmacology* / Q000627:therapeutic use; D006801:Humans; D066298:In Vitro Techniques; D008171:Lung Diseases / Q000150:complications / Q000188:drug therapy*; D008826:Microbial Sensitivity Tests; D009161:Mycobacterium / Q000187:drug effects*; D009164:Mycobacterium Infections / Q000150:complications / Q000188:drug therapy*; D009894:Opportunistic Infections / Q000150:complications / Q000188:drug therapy*; D011237:Predictive Value of Tests; D012293:Rifampin / Q000494:pharmacology* / Q000627:therapeutic use; D016896:Treatment Outcome
D000995:Antitubercular Agents; D004977:Ethambutol; D012293:Rifampin