Introduction

Abstract

Diseases caused by mycobacteria are on the increase, not only in developing countries such as Africa or India but also in Europe. According to a report by WHO on the tuberculosis epidemic of 1997, a third of the world’s population is infected with the tuberculosis bacillus, and about eight million people became sick with tuberculosis in 1996. Thus, this disease, that had virtually disappeared a few years ago, now represents the world’s leading infectious killer and has become a new global emergency. Furthermore, mycobacteria previously regarded as harmless can now provoke heavy mycobacterioses in immunocompromized AIDS patients. In addition, evidence of unusual mycobacterioses occurring occasionally in immunocompetent individuals has enlarged the spectrum of mycobacteria that can cause disease in humans and animals. Because the majority of these species are environmentally derived, the ecology of mycobacteria has gained in importance. Recently, more detailed studies into the conditions under which mycobacteria can survive and develop in a variety of environments have been carried out.