Once these complexes are formed, they are very resistant to decolorization with acid alcohols or strong mineral acids, and are thus termed acid fast. Although the exact mechanism responsible for the acid fastness of mycobacteria is unknown, it is largely attributed to the presence of mycolic acids in the outer cell wall. Figure 10 and Figure 11 summarize the current testing algorithms for organisms received for identification and primary cultures, respectively. The mycobacteria are a diverse group of organisms that cause a variety of systemic and localized infections. In 1990, the Centers for Disease Control reported a reversal in the previously reported decrease in the incidence of infections caused by Mycobacterium tuberculosis .
M. tuberculosis is transmitted by inhalation of infected droplet nuclei.
This disease has increased over the last decade and is associated with considerable morbidity and mortality. Accurate, timely diagnosis is essential in halting the current tuberculosis epidemic. These organisms are usually resistant to INH, but respond to rifabutin and macrolides. Accurate identification is essential to successful therapeutic outcome. It is less responsive to traditional anti- tuberculosis therapy.