Low sensitivity of Ziehl-Nielsen staining for acidoresistent bacteria and timeconsuming culture methods resulted in the introduction of more rapid and sensitive ways of detection of mycobacteria. In 1993 the laboratories of the department of medical genetics in Hradec Králové started with examinations of mycobacteria using „home-made“ PCR. In the course of three years (1994 - 1996) 182 children being suspected of the specific inflammatory process and 28 children suffering from local complications after BCG vaccination were examined. 15 of 182 patients were diagnosed by the physician as tuberculosis, avian mycobacteriosis or status after treated tuberculosis. Among the 15 children 9 were positive in PCR tests, one had a positive culture and no patient had a positive Ziehl-Nielsen staining. In two children (brother and sister) mycobacterial DNA was detectable even one year after treatment of the primary complex. In two cases the PCR examination played the key role in the early diagnosis. Continual experimental determination of PCR parameters (specificity, sensitivity) were emphasised. The sensitivity was determined as 100 mycobacteria per sample and the parameter is checked continuously by internal positive control.

        Key words: PCR, mycobacterium, specificity, sensitivity