[Changes in the primary resistance to Mycobacterium tuberculosis in Piedmont 1965-1979]

A comparison is made of the data drawn from Hospital statistics for the period 1965-79 with regard to antibiograms from patients with first T. B. observations. A progressive reduction in primary resistance in the general sense was noted, with an increase in the case of RAMP only. There was a constant decrease for INH, PAS and ETB, whereas SM, KM and CS values were stationary. The conclusion is drawn that the reduction in primary resistance notwithstanding the continual employment of these drugs must be attributed to the fact that the resistant mycobacteria have depressed proliferative capacity and virulence. Primary resistance, therefore, while a good pointer to the epidemiology of T.B. infection, is not a cause for concern from the therapeutic standpoint.