Mycobacterium tuberculosis complex
Mycobacterium tuberculosis complex
The Mycobacterium tuberculosis complex (M. tuberculosis complex, MTBC) is a group of closely related species of bacteria that includes Mycobacterium tuberculosis, the causative agent of tuberculosis. Pronounced as my-co-bac-te-ri-um tu-ber-cu-lo-sis com-plex. The etymology of the term comes from the genus Mycobacterium, which is derived from the Greek mykes (fungus) and bakterion (small rod), and tuberculosis, which is derived from the Latin tuberculum (small swelling).
Species
The MTBC includes the following species:
- Mycobacterium tuberculosis - the primary cause of tuberculosis in humans.
- Mycobacterium bovis - causes tuberculosis in cattle and other animals, and can also infect humans.
- Mycobacterium africanum - primarily found in West Africa, it can cause tuberculosis in humans.
- Mycobacterium microti - primarily infects voles, but can also cause tuberculosis in humans.
- Mycobacterium canettii - a rare species that can cause tuberculosis in humans.
- Mycobacterium pinnipedii - primarily infects seals and sea lions, but can also infect humans.
- Mycobacterium caprae - primarily infects goats, but can also infect humans.
Pathogenesis
The species in the MTBC are aerobic bacteria that are capable of surviving in a variety of environments within the host. They are transmitted primarily through the air when people who have an active TB infection cough, sneeze, or otherwise transmit respiratory fluids through the air. Most infections do not have symptoms, in which case it is known as latent tuberculosis. About 10% of latent infections progress to active disease which, if left untreated, kills about half of those affected.
Diagnosis
Diagnosis of tuberculosis is challenging and requires a combination of medical imaging (primarily chest X-rays), a tuberculin skin test (TST), blood tests, as well as microscopic examination and microbiological culture of bodily fluids.
Treatment
Treatment of tuberculosis is difficult and requires administration of multiple antibiotics over a long period of time. Antibiotic resistance is a growing problem in multiple drug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB).
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