PYROLYSIS MASS-SPECTROMETRY - A PREDICTOR OF CLINICAL-RESPONSE TO TREATMENT IN PULMONARY OPPORTUNIST MYCOBACTERIAL INFECTION - PRELIMINARY WORK WITH M-MALMOENSE

Pyrolysis mass spectrometry (Py-MS) yields data reflecting overall cel l composition. The changes in composition induced by treatment with ri fampicin and ethambutol, alone and in combination, were investigated f or a collection of seven strains of Mycobacterium malmoense from pulmo nary infections. Two strains, both from patients that had responded to therapy with this combination, showed large changes in composition fr om control, untreated cultures. The difference was particularly marked for the ethambutol treated cultures. Four strains, all from patients who had failed to respond to therapy with this combination, showed min imal changes in composition for all treatments. The remaining strain a lso showed minimal treatment-induced change, but, for this patient, th erapy with the combination had proved successful. Minimum inhibitory c oncentrations (MICs) were determined radiometrically. All strains show ed MICs < 0.5 mu g/mL for rifampicin (sensitive) and of 8 mu g/mL for ethambutol (resistant). MIC results did not correlate with clinical re sponse, whereas the Py-MS results correlated with clinical response fo r six of the seven isolates. Py-MS may have a role in predicting effec tive therapy for this problem group.