Mycobacterium tuberculosis, SEM

Coloured scanning electron micrograph (SEM) of Mycobacterium tuberculosis, MDR-TB and XDR-TB strain, rod bacterium (prokaryote). Mycobacterium tuberculosis is the primary causative agent of human tuberculosis (TB). Contaminated respiratory secretions transmit the infection between humans. In the past few years drug resistant strains, MDR-TB and XDR-TB strains have emerged, especially in developing countries. MDR-TB (Multidrug Resistant TB) strains are resistant to at least the two first-line TB drugs, isoniazid and rifampicin. XDR-TB, or Extensive Drug Resistant TB (also known as Extreme Drug Resistance) is a strain that is also resistant to three or more of the six classes of second-line drugs. Drug-resistant TB is a public health issue in many developing countries, as treatment is longer and requires more expensive drugs. Magnification: x3,400 when shortest axis printed at 25 millimetres.