Rash on the chest and abdomen caused by leprosy
Rod-shaped Bacillus subtilis
M. leprae, one of the causative agents of leprosy: As an acid-fast bacterium, M. leprae appears red when a Ziehl–Neelsen stain is used.
Phylogenetic tree of Bacteria, Archaea and Eucarya. The vertical line at bottom represents the last universal common ancestor.
Testing for loss of sensation with monofilament
Bacteria display many cell morphologies and arrangements
MDT antileprosy drugs: standard regimens from 2010
The range of sizes shown by prokaryotes (Bacteria), relative to those of other organisms and biomolecules.
New cases of leprosy in 2016.
Structure and contents of a typical Gram-positive bacterial cell (seen by the fact that only one cell membrane is present).
G. H. A. Hansen, discoverer of M. leprae
An electron micrograph of Halothiobacillus neapolitanus cells with carboxysomes inside, with arrows highlighting visible carboxysomes. Scale bars indicate 100 nm.
Distribution of leprosy around the world in 1891
Helicobacter pylori electron micrograph, showing multiple flagella on the cell surface
Two lepers denied entrance to town, 14th century
Bacillus anthracis (stained purple) growing in cerebrospinal fluid
Medieval leper bell
Many bacteria reproduce through binary fission, which is compared to mitosis and meiosis in this image.
A 24-year-old man with leprosy (1886)
A culture of ''Salmonella
Father Damien on his deathbed in 1889
A colony of Escherichia coli
Paucibacillary leprosy (PB): Pale skin patch with loss of sensation
Helium ion microscopy image showing T4 phage infecting E. coli. Some of the attached phage have contracted tails indicating that they have injected their DNA into the host. The bacterial cells are ~ 0.5 µm wide.
Skin lesions on the thigh of a person with leprosy
Transmission electron micrograph of Desulfovibrio vulgaris showing a single flagellum at one end of the cell. Scale bar is 0.5 micrometers long.
Hands deformed by leprosy
The different arrangements of bacterial flagella: A-Monotrichous; B-Lophotrichous; C-Amphitrichous; D-Peritrichous
Leprosy in Tahiti, c. 1895
Streptococcus mutans visualised with a Gram stain.
A 26-year-old woman with leprous lesions
Phylogenetic tree showing the diversity of bacteria, compared to other organisms. Here bacteria are represented by three main supergroups: the CPR ultramicrobacterias, Terrabacteria and Gracilicutes according to recent genomic analyzes (2019).
A 13-year-old boy with severe leprosy
Overview of bacterial infections and main species involved.
Colour-enhanced scanning electron micrograph showing Salmonella typhimurium (red) invading cultured human cells
In bacterial vaginosis, beneficial bacteria in the vagina (top) are displaced by pathogens (bottom). Gram stain.
Antonie van Leeuwenhoek, the first microbiologist and the first person to observe bacteria using a microscope.

Leprosy, also known as Hansen's disease (HD), is a long-term infection by the bacteria Mycobacterium leprae or Mycobacterium lepromatosis.

- Leprosy

However, several species of bacteria are pathogenic and cause infectious diseases, including cholera, syphilis, anthrax, leprosy, tuberculosis, tetanus and bubonic plague.

- Bacteria

2 related topics


Chest X-ray of a person with advanced tuberculosis: Infection in both lungs is marked by white arrow-heads, and the formation of a cavity is marked by black arrows.


Chest X-ray of a person with advanced tuberculosis: Infection in both lungs is marked by white arrow-heads, and the formation of a cavity is marked by black arrows.
The main symptoms of variants and stages of tuberculosis are given, with many symptoms overlapping with other variants, while others are more (but not entirely) specific for certain variants. Multiple variants may be present simultaneously.
Scanning electron micrograph of M. tuberculosis
Public health campaigns in the 1920s tried to halt the spread of TB.
Robert Carswell's illustration of tubercle
Microscopy of tuberculous epididymitis. H&E stain
M. tuberculosis (stained red) in sputum
Mantoux tuberculin skin test
Tuberculosis public health campaign in Ireland, c. 1905
Tuberculosis phototherapy treatment on 3 March 1934, in Kuopio, Finland
Egyptian mummy in the British Museum – tubercular decay has been found in the spine.
Robert Koch discovered the tuberculosis bacillus.
Painting The Sick Child by Edvard Munch, 1885–86, depicts the illness of his sister Sophie, who died of tuberculosis when Edvard was 14; his mother too died of the disease.
Number of new cases of tuberculosis per 100,000 people in 2016.<ref>{{cite web |title=Tuberculosis incidence (per 100,000 people) |url=https://ourworldindata.org/grapher/incidence-of-tuberculosis-sdgs |website=Our World in Data |access-date=7 March 2020 |archive-date=26 September 2019 |archive-url=https://web.archive.org/web/20190926041419/https://ourworldindata.org/grapher/incidence-of-tuberculosis-sdgs |url-status=live }}</ref>
Tuberculosis deaths per million persons in 2012
Tuberculosis deaths by region, 1990 to 2017.<ref>{{cite web |title=Tuberculosis deaths by region |url=https://ourworldindata.org/grapher/tuberculosis-deaths-region |website=Our World in Data |access-date=7 March 2020 |archive-date=8 May 2020 |archive-url=https://web.archive.org/web/20200508204644/https://ourworldindata.org/grapher/tuberculosis-deaths-region |url-status=live }}</ref>

Tuberculosis (TB) is an infectious disease usually caused by Mycobacterium tuberculosis (MTB) bacteria.

NTM cause neither TB nor leprosy, but they do cause lung diseases that resemble TB.

A photomicrograph of a stool that has shigella dysentery. This bacteria typically causes foodborne illness.


Any organism or agent that can produce disease.

Any organism or agent that can produce disease.

A photomicrograph of a stool that has shigella dysentery. This bacteria typically causes foodborne illness.
Magnified 100× and stained. This photomicrograph of the brain tissue shows the presence of the prominent spongiotic changes in the cortex, with the loss of neurons in a case of a variant of Creutzfeldt-Jakob disease (vCJD)
Two pinworms next to a ruler, measuring in 6 millimeters in length
Brown rot fungal disease on an apple. Brown rot typically target a variety of top-fruits.
A structure of Doxycycline a tetracycline-class antibiotic

Typically, the term pathogen is used to describe an infectious microorganism or agent, such as a virus, bacterium, protozoan, prion, viroid, or fungus.

Pathogenic bacteria also cause infections such as tetanus, typhoid fever, diphtheria, syphilis, and leprosy.