![]() tuberculosis complex can be killed by the host's immune system active TB disease can occur in different areas of the body such as regional lymph nodes, lung, kidneys, brain, larynx, and bone or latent TB infection (LTBI) may be established. Infection occurs when a person (or animal) inhales 1- to 5-μm droplet nuclei containing tubercle bacilli that reach the alveoli of the lungs. Tuberculosis (TB) is caused by a group of closely related, slowly growing mycobacteria collectively named the Mycobacterium tuberculosis complex, which infect a large spectrum of mammals, including humans. From 41 valid species in 1980, the genus Mycobacterium currently encompasses almost 200 recognized species and subspecies ( 2, – 6), many of which either can cause clinical disease, have been associated with disease, or have been isolated from clinical specimens without any known clinical correlation. This feature is intrinsically linked to their pathogenic ability to infect humans, and therefore, all strict pathogens and most opportunistic pathogens belong to the evolutionary branch of slowly growing mycobacteria ( 2, – 4). Gene sequence similarities within the genus (>94.3% for the 16S rRNA gene) and robust phylogenetic reconstructions using concatenated sequences of housekeeping genes have confirmed the natural division between slowly and rapidly growing mycobacteria and have also demonstrated that all slowly growing mycobacteria belong to a single evolutionary branch that emerged from the rapidly growing mycobacteria. The Mycobacterium genus includes strict pathogens, potential or opportunistic pathogens, and nonpathogenic, saprophytic species. Compared to most other bacteria, mycobacteria are slowly growing, requiring at least 5 days of incubation, with many requiring 1 or more weeks for visible growth of note, some do not grow at all on solid media ( 1). Some species are pigmented yellow or orange when cultured, and this pigment may be constitutive (i.e., scotochromogenic) or induced only with exposure to light (i.e., photochromogenic), while other species never produce pigment (i.e., nonphotochromogenic). They are nonmotile, and most of them are straight or slightly curved rods, with only a small number of species exhibiting some branching. are aerobic, non-spore-forming, Gram-positive, acid-fast bacilli (AFB). This characteristic enables these bacteria to be differentiated from other bacteria based on staining techniques since the high mycolic acid content in the cell wall makes organisms resistant to decolorization with acid alcohol (i.e., “acid fast”). contain mycolic acids in their cell wall and share this characteristic with bacteria of other genera such as Gordonia, Nocardia, Rhodococcus, and Tsukamurella. Furthermore, the review considers the ever-changing health care delivery system and stresses the laboratory's need to adjust and embrace molecular technologies to provide shorter turnaround times and a higher quality of care for the patients who we serve. This review describes contemporary methods for the laboratory diagnosis of mycobacterial diseases. National Institutes of Health reported an increase from 20 to 47 cases/100,000 persons (or 8.2% per year) of pulmonary nontuberculous mycobacterial disease among adults aged 65 years or older throughout the United States, with 181,037 national annual cases estimated in 2014. Pulmonary nontuberculous mycobacterial disease is an emerging public health challenge. In 2015, the World Health Organization reported 2,037 new cases of Buruli ulcer, with most cases being reported in Africa. India, Brazil, and Indonesia reported the most leprosy cases. ![]() In 2015, there were 174,608 new case of leprosy worldwide. In 2016, a total of 9,287 new TB cases were reported in the United States. In 2015, globally, almost 10 million people developed TB, and almost half a million patients suffered from its multidrug-resistant form. ![]() Mycobacteria are the causative organisms for diseases such as tuberculosis (TB), leprosy, Buruli ulcer, and pulmonary nontuberculous mycobacterial disease, to name the most important ones. ![]()
0 Comments
Leave a Reply. |