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CHAPTER 1.1.19 ehT

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The Genus Mycobacterium—Medical BEATRICE SAVIOLA AND WILLIAM BISHAI

Introduction The genus Mycobacterium encompasses a number of medically important species that exact an alarming toll in human morbidity and mortality. Indeed the World Health Organization (WHO) estimates that nearly one third of the world’s population (1.8 billion people) are infected with Mycobacterium tuberculosis, the cause of tuberculosis (TB) (http://www.who.org). In 1993, the WHO declared a global emergency owing to the fact that TB was epidemic in many areas of the world. Other mycobacterial diseases continue to plague the world’s populations as well. Mycobacterium leprae, the cause of leprosy, persists in developing countries, and other mycobacteria (ordinarily nonpathogens) have now become threats to individuals infected with the human immunodeficiency virus (HIV). Mycobacteria have shaped the course of human history. Indeed until 1900, TB was one of the chief causes of death in Europe and the Americas. The nature of the disease, however, remained poorly understood and as a testimonial to this fact its contagiousness was the subject of heated debate well into the 18th and 19th centuries. For many years, psychological and inherited factors were thought to predispose individuals to the disease. However, others thought that a contagious agent was the culprit. This debate ended only after the bacillus Mycobacterium tuberculosis was identified as the causative agent of TB. Jean Antoine Villemin in 1868 was the first to transmit TB from man to rabbit (Haas and Haas, 1996). As a military doctor, he had observed that many young healthy military personnel housed in barracks eventually succumbed to TB. He also noted that a disproportionate number of individuals with active TB were prisoners, industrial workers, members of cloistered religious orders as well as military personnel; all of them were housed together with many other people. Villemin speculated that TB was transmissible. He used material (gray and soft tubercles) from humans who had succumbed to TB as well as blood and sputum from tuberculous patients to infect rabbits. The inoculated rabbits indeed

developed pathologic evidence of tuberculosis. Then in 1882, Robert Koch was the first to view Mycobacterium tuberculosis through a light microscope. He was then able to grow M. tuberculosis in pure culture, infect guinea pigs with the bacilli, and reisolate bacteria from these animals (Adler and Rose, 1996). Thus a new era of mycobacteria research was born. In Europe and the United States, a sanatorium movement was underway by the 1890s to isolate and cure those patients having TB. Edward Livingston Trudeau started one of the first and most successful of the sanatoria in the United States (Davis, 1996). After providing hospice care for his consumptive brother, Dr. Trudeau was stricken with that same disease. He fled to the Adirondack Mountains believing that fresh air, nutritious food and exercise would restore his health. As hoped, his disease symptoms abated and his hea