Results from cation and mass fingerprint analysis of single cells and from ATP measurements of M. leprae for drug sensitivity testing: a comparison.

The physiologic states of Mycobacterium leprae isolated from patient biopsies were studied using single cell mass spectrometry by laser microprobe mass analysis (LAM-MA) and ATP bioluminescence assay. The changes in the physiologic state of M. leprae after the patients had been treated with dapsone (DDS) monotherapy were also studied. The shift of the low intracellular Na+, K+-ratio of untreated M. leprae cells to higher values under DDS therapy, as measured from a limited number of single bacteria, correlates with a decrease in the ATP content. Further information on the influence of the drug could be drawn from the multivariate analysis of mass fingerprints of the organic matrix of the cells. Evidence is provided that the combination of the measurement of the intracellular cation ratios and of the mass fingerprint analysis could give fast answers to the question of drug resistance and to the persister hypothesis. The ATP bioluminescence assay and the single cell mass analysis should be alternatives to the mouse foot pad test.