Chlamydial infection
Chlamydia represent a large group of obligate intracellular parasites very close to gram-negative bacteria. They can be considered as gram-negative bacteria, which have lost the ability to synthesize ATP, guanosine triphosphate( GTP) and a number of other enzyme systems, in other words, have lost the ability to generate metabolic energy. This defect causes their intracellular growth, due to which they have access to energy-rich intermediates of host cell metabolism. In the Chlamydiaceae family there are two genus - Chlamydia and Chlamydophila, and they differ in phenotypic characteristics.
The genus Chlamydia includes three species: Chlamydia trachomatis, Chlamydia muridarum and Chlamydia suis. Chlamydia trachomatis - exclusively a human parasite, causes trachoma, urogenital diseases, some forms of arthritis, conjunctivitis and pneumonia of newborns. C. trachomatis has two biovars: trachoma( 14 serovars) and LGV( 4 serovars).Other types of Chlamydia do not cause diseases in humans.
The genus Chlamydophila is composed of six species: C. psittaci, C. pneumoniae, C. pecorum, C. abortus, C. caviae and C. felis.
Chlamydophila pecorum is an exceptionally causative agent of animal diseases. Several strains of C. pecorum have been isolated from marsupials( koala), ruminant mammals and pigs.
Chlamydophila pneumoniae is the causative agent of respiratory infections. This species has three biovars: TWAR( Taiwan acute respiratory), Koala and Equine, their names are associated with a source of isolating strains. TWAR strains mainly become pathogens of the respiratory tract in humans, causing mainly acute and chronic bronchitis and pneumonia.
Chlamydophila psittaci includes strains for which the main hosts are birds. All these strains can be transmitted to a person, causing psittacosis. C. psittaci includes eight serovars, many of them can parasitize several species of birds.
Chlamydophila abortus is named for the underlying condition caused by this pathogen. This species is common among ruminants and mostly colonizes the placenta. Sporadic abortions caused by C. abortus are registered in women who worked with sheep, they were called "gestational psittacosis".
Chlamydophila felis causes rhinitis and conjunctivitis in domestic cats( Felis catus).Zoonotic infections caused by C. felis, in humans, manifested in the form of conjunctivitis, were noted.
Chlamydophila caviae was first isolated from the guinea pig conjunctiva( Cavia cobaya) and was later described in several animals of this species.