Determination of in vivo and in vitro drug effects of mycobacteria from the mass spectrometric analysis of single organisms.

Laser microprobe mass analysis of single bacterial organisms allows the determination of their intrabacterial ratio of sodium-to-potassium ions and the registration of fragment ions originating from their organic bacterial cell matrices as mass fingerprint spectra. It has been established previously that the intrabacterial cation ratio provides information on the physiological state of an individual bacterial cell. In the present experiments it is also shown, with different cultivable mycobacterial species and strains (drug sensitive and resistant) exposed to various drugs, that data derived from the evaluation of the mass fingerprint spectra reflect changes in the degree of impairment. The analysis of Mycobacterium leprae derived from a limited number of skin biopsies of lepromatous/borderline lepromatous leprosy patients under World Health Organization-recommended multiple-drug therapy (WHO/MDT) showed impairment of the organisms with both of the methods of measurement in proportion to the duration of treatment except in one case. In one M. leprae population from a patient who had been treated for 19 months, the fingerprint evaluation gave the first evidence for an insufficient response to treatment. This was further confirmed by the unusual frequency distribution of the Na+,K+ ratios which revealed the existence of two subpopulations, one impaired and one unimpaired.