On the development of mycobacterial infections II. Changing mycobacterial infection spectrum in the Cologne area 1983-1993

Abstract

The overall detection rate of mycobacteria in the Cologne area did not change between 1983 and 1993. But a significant shift of the rate of Mycobacterium tuberculosis to nontuberculous mycobacteria, especially Mycobacterium avium-intracellulare complex, could be observed. Whereas the portion of Mycobacterium tuberculosis fell during these years from about 90% to 50-70% the portion of Mycobacterium avium-intracellulare increased steadily from 0 to 23% of all mycobacteria positive patients. The portion of tuberculosis patients positive for HIV remained constantly at 5-7% until 1992. Whether the 10% in 1993 signalizes a definitive increase remains to be proven. HIV positive patients with the diagnosis mycobacteria show another development. Whereas Mycobacterium tuberculosis is isolated constantly from about 2-3% of all HIV positive patients, the Mycobacterium avium-intracellulare complex increased from 0 to 10%. As methodical factors play a special role in the diagnostic procedure of mycobacteria, we evaluated some of the newer techniques for our routine laboratory: The well-known high sensitivity and specificity of the DNA probes (Gen-probe system) was confirmed, and by the radiometric culture system, in fact, the ubiquitous mycobacteria were detected much better. Otherwise from one third of special materials Mycobacterium tuberculosis and Mycobacterium bovis grew only on the conventional solid media. The susceptibility testing of 925 Mycobacterium tuberculosis strains revealed a rate of 10% (95 strains) with resistance to one antituberculotic drug only and 3% (29 strains) with resistance to two or more drugs. Only 0.9% (8 strains) were resistant to isoniacid and rifampicin (multidrug-resistant strains) indicating that drug resistance of Mycobacterium tuberculosis is still no serious problem in our region.