Chlamydia is a genus of bacteria in the Verrucomicrobia group. According to the Microbe Wiki supported by Kenyon College, the various strains of chlamydia vary by nearly 200 genes. Though they are classified as gram-negative bacteria, they are actually difficult to type. They are closely related to aerobic intracellular pathogens. The cell wall of the bacteria prevents phagolysosome fusion in phagocytes and they lack the ability to produce ATP (meaning they require a living host cell for energy), leading to their previous misidentification as viruses.
Life cycle and other characteristics
Chlamydia bacteria alternate between being a non-replicating and infectious entity (elementary body) to being a replicating, non-infectious entity (reticulate body). The transition occurs when the bacterium interacts with glycogen. During the reticulate phase, the bacteria divide every two to three days, being released as an elementary body to infect new cells. The bacteria incubate in the host for one to three weeks.
Human infection with chlamydia bacteria
Three varieties of chlamydia bacteria infect humans. The less common two, according to KidsHealth, are Chlamydia pneumoniae and Chlamydia psittaci. According to the Centers for Disease Control (CDC), the pneumoniae strain causes respiratory illness, such as pneumonia and bronchitis, and it can be passed to others via coughing and sneezing. The psittaci strain is passed to humans from birds, causing an infection called psittacosis. According to Medscape, human-to-human transmission is rare and exposure to the bacterium is considered an occupational hazard of those who work with zoos and aviaries. The disease is also called ornithosis.
The third strain of chlamydia bacteria to infect humans, Chlamydia trachomatis, is the most common sexually transmitted infectious agent. This bacterial strain is also passed to children during birth if their mother is infected and can be passed via any intimate contact, including in the throat. Women are particularly susceptible to infection, with re-infection being a concern when partners are not also treated, according to the U.S. Dept of Health and Human Services.
This sexually transmitted strain is usually known simply as Chlamydia. Three-quarters of Chlamydia infections cause no symptoms. This leads to under-treatment, which can have long-term complications, particularly in women. Pelvic inflammatory disease and permanent damage to the tissues of the urinary and reproductive systems are possible with long-term infection, according to the CDC. Chlamydia infections can be cured with antibiotics.
Rodent homolog of Chlamydia for research
A new species of chlamydia, springing from the trachomatis strain in rodents, is Chlamydia muridarum. This strain infects mice and hamsters, causing pneumonitis. It is a gram-negative bacterium with similarities to human Chlamydia trachomatis. Some microbiologists think that studying the muridarum strain in rodents will help with understanding the human strain.