''Chlamydia abortus'' is a species in

Chlamydiota The Chlamydiota (synonym Chlamydiae) are a bacterial phylum and class whose members are remarkably diverse, including pathogens of humans and animals, symbionts of ubiquitous protozoa, and marine sediment forms not yet well understood. All of ...

that causes abortion and fetal death in mammals, including humans. It was originally proposed as ''Chlamydophila abortus'' by a split from ''Chlamydia psittaci'' in 1999, based on differences of pathogenicity and

DNA–DNA hybridization In genomics, DNA–DNA hybridization is a molecular biology technique that measures the degree of genetic similarity between DNA sequences. It is used to determine the genetic distance between two organisms and has been used extensively in phylo ...

. The assignment of ''Cp. abortus'' and ''Cp. psittaci'' to a new genus ''Chlamydophila'' was based on a lack of evident

glycogen Glycogen is a multibranched polysaccharide of glucose that serves as a form of energy storage in animals, fungi, and bacteria. It is the main storage form of glucose in the human body. Glycogen functions as one of three regularly used forms ...

production and on resistance to the

antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy ...

sulfadiazine Sulfadiazine is an antibiotic. Used together with pyrimethamine, a dihydrofolate reductase inhibitor, it is the treatment of choice for toxoplasmosis, which is caused by a protozoan parasite. It is a second-line treatment for otitis media, pr ...

. In 2015, this new genus was reverted to ''Chlamydia'', but ''C. abortus'' remains as a distinct species.

In humans

There are approximately one or two cases of ''C. abortus'' infection in pregnant women diagnosed in the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...

per year. Typically transmission occurs from contact with livestock who have recently given birth. The true prevalence in humans is unknown because the routine

serological Serology is the scientific study of serum and other body fluids. In practice, the term usually refers to the diagnostic identification of antibodies in the serum. Such antibodies are typically formed in response to an infection (against a given mi ...

antibody An antibody (Ab) or immunoglobulin (Ig) is a large, Y-shaped protein belonging to the immunoglobulin superfamily which is used by the immune system to identify and neutralize antigens such as pathogenic bacteria, bacteria and viruses, includin ...

test ( complement fixation test) is unable to distinguish between ''C. abortus'' and other more common species such as ''

Chlamydia trachomatis ''Chlamydia trachomatis'' () is a Gram-negative, Anaerobic organism, anaerobic bacterium responsible for Chlamydia infection, chlamydia and trachoma. ''C. trachomatis'' exists in two forms, an extracellular infectious elementary body (EB) and an ...

''.

In other animals

''Chlamydia abortus'' is endemic among

ruminant Ruminants are herbivorous grazing or browsing artiodactyls belonging to the suborder Ruminantia that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microb ...

s such as cows and sheep and has been associated with

abortion Abortion is the early termination of a pregnancy by removal or expulsion of an embryo or fetus. Abortions that occur without intervention are known as miscarriages or "spontaneous abortions", and occur in roughly 30–40% of all pregnan ...

in a horse, a rabbit, guinea pigs, mice, pigs and humans. Infected females shed bacteria near the time of ovulation, so ''C. abortus'' is transmitted orally and sexually among mammals. All "typical" ''C. abortus'' strains were isolated or PCR-amplified from the

placenta The placenta (: placentas or placentae) is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas, and waste exchange between ...

or fetal organs after spontaneous abortion. ''C. abortus'' infection generally remains unapparent until an animal aborts late in gestation or gives birth to a weak or dead fetus. ''Chlamydia abortus'' has been isolated from birds. For a discussion of this intermediate status, see .

Genome structure

''Chlamydia abortus'' has a relatively small

genome A genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as ...

that contains 1.14 Mbp with 961

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

coding genes.

In humans

In other animals

Genome structure

References

Further reading