Biological properties of chlamydia. Chlamydia. Chlamydia. Life cycle of chlamydia. Chlamydia classification Chlamydia taxonomy
1) elementary bodies - small (0.2 - 0.5 microns) electron-dense spherical structures with a compact nucleoid and a rigid three-layer cell wall;
2) initial (initial), or reticular, bodies - large (0.8 - 1.5 microns in diameter) spherical formations having a mesh structure with a thin cell wall and a fibrillar nucleoid;
3) intermediate bodies - an intermediate stage between elementary and reticular bodies.
Elementary bodies are infectious, and reticular bodies are a vegetative form of chlamydia. Vegetative forms reproduce by binary fission intracellularly, but are not infectious when released from the host cell. Life cycle chlamydia begins with the elementary bodies being phagocytosed by the host cell, and then within a few hours they reorganize, increase in size and turn into reticular forms that multiply by transverse division. The resulting daughter forms also reproduce by binary fission. The life cycle ends when the emerging intermediate forms are reorganized (compacted), reduced in size and transformed into elementary bodies. Propagating inside cytoplasmic vesicles, chlamydia form microcolonies surrounded by a membrane arising from the invagination of the cell membrane during phagocytosis of the elementary body. All 3 stages of chlamydia development are found in the composition of microcolonies. There can be several microcolonies in one cell, which are formed in the case of phagocytosis of several elementary bodies. After rupture of the vesicle wall and host cell membrane, newly formed chlamydia are released, and elementary bodies, infecting other cells, repeat the development cycle. For microscopic detection of chlamydia in infected cells (tissues), various staining methods are used: Romanovsky - Giemsa, Castenada, Machiavello, etc. When stained according to Romanovsky - Giemsa, they become blue or purple. However, chlamydia are also clearly visible in the unstained state when microscopy of wet preparations under glass using a phase-contrast optical system. Under optimal growth conditions in eukaryotic cells, the life cycle of chlamydia is 17–40 hours. Chlamydia reproduce well in the yolk sac of chicken embryos at temperatures from 33 to 41 ° C (depending on the species), as well as in cell cultures of various vertebrates. The content of G+C in Chlamydia DNA varies from 39 to 45 mol %, the ratio of RNA/DNA in elementary bodies is 2 times less than in reticular ones. At C. trachomatis two important metabolic traits were discovered: the ability to synthesize glycogen and folic acid precursors, according to which (taking into account other features) they are easily differentiated from other species - C. psittaci and C. pneumoniae(Table 51).
Table 51
Differential signs of three types Chlamydia
The causative agents of trachoma, conjunctivitis (blennorrhea with inclusions), inguinal lymphogranulomatosis (Nicolas-Favre disease), ornithosis belong to the genus Chlamydia, family Chlamydiaceae, order Chlamydiales; they contain DNA and RNA, nucleoproteins, lipids, carbohydrates.
Three stages are observed in the development cycle of chlamydia: 1) small (0.2-0.4 microns) elementary bodies surrounded by a three-layer wall, which contain the genetic material of the nucleoid and ribosome in a compact state; 2) primary bodies, large (0.8-1.5 microns), have nucleoid fibrils and ribosomal elements, are covered with a thin wall, multiply by fission; daughter cells are reorganized into elementary bodies, which can be extracellular and penetrate into other cells; 3) intermediate (transient) stage between primary and elementary bodies. small
(elementary) bodies have infectious properties, large (primary) bodies perform a vegetative function, growth, reproduction and maturation of chlamydia are completed within 40 hours.
Monkeys are sensitive to the causative agent of trachoma, in which, when infected in the conjunctiva, experimental trachoma develops, similar to the disease in humans; some strains can multiply in the lungs of mice and guinea pigs infected intranasally, as well as when infected subcutaneously in guinea pigs and intracerebral in mice. The pathogen reservoir is a person. The disease in humans is accompanied by blepharokeratoconjunctivitis. Patients develop chronic inflammation of the connective membrane of the eyes, tissue hyperplasia and hypertrophy of follicles that look like transparent grains. In severe cases, due to hypertrophy of the follicles, the conjunctiva looks like a frog's caviar. In the future, scarring of the follicles occurs.
Trachoma is transmitted through contact with patients through a towel, dirty hands, when washing in a common basin, as well as flies.
Laboratory diagnostics carried out by detecting inclusions in the cells of the epithelium of the conjunctiva.
Treatment is successfully carried out with antibiotics (tetracyclines, erythromycin) and sulfa drugs.
Prevention includes the timely detection and full treatment of patients, dispensary services for outbreaks, improvement of working and living conditions, and raising the material and cultural level of the population. A very high incidence of trachoma is noted in India and other Asian countries, in Africa. Trachoma affects 400-500 million people living in developing countries; it is the main cause of blindness.
Conjunctivitis of newborns, or blenorrhea with inclusions, is caused by Chl.trachomatis (Fig. 116.9), the disease proceeds with phenomena of infiltration of the conjunctiva, especially the lower eyelid. The duration of the acute phase is 10-15 days, but noticeable infiltration persists for 2-3 months or longer. The source of infection are mothers in whom the pathogen persists in the genitourinary system and is transmitted during childbirth to newborn children. Adults become infected by swimming in small ponds and non-chlorinated pools. The disease in them manifests itself in the form of acute follicular conjunctivitis and lasts about a year. Treatment is with sulfa drugs and antibiotics. The introduction of silver nitrate for the prevention of gonorrheal blennorrhea does not prevent conjunctivitis with inclusions.
The causative agent of venereal lymphogranulomatosis is Chl.trachomatis. The disease is sexually transmitted, occurs in hot subtropical countries. There are no cases of the disease in the USSR. This microorganism can also cause urethritis, proctitis, arthritis.
Laboratory diagnostics is carried out using microscopy with the processing of smears according to Romanovsky-Giemsa. Complement fixation reaction and allergic test are of diagnostic value. Use intracerebral infection of white mice, which develop meningitis with a fatal outcome.
Treatment. Apply tetracyclines, penicillin and sulfanilamide preparations.
The causative agent of ornithosis - Chl.psittaci - causes diseases in many species of birds. The causative agent was discovered in 1933 by K. Maner.
The morphology and method of reproduction are the same as in the entire genus Ciatusha. In smears-imprints or sections from organs, microorganisms are located in the form of clusters surrounded by a vesicular membrane. They can be detected by staining according to Romanovsky-Giemsa, in the cells of the lymphoid-macrophage system, or extracellularly when they break (see Fig. 116.4). The content of G + C in the DNA of the nucleoid is 39-45%. Chlamydia develops in the yolk sac of chicken embryos or white mice, as well as in tissue culture and in tumor cells at 39°C.
Chlamydia have two antigens: thermostable, which is common to the group of ornithosis-psittacosis-lymphogranulomatosis, and thermolabile, decomposing at 60°C and containing a protein substance.
The resistance is very high. Chlamydiae remain alive for 2 years at -70°C. Infected tissues at 4°C continue to be infectious for several weeks. Heating at a temperature of 60-70 ° C kills chlamydia within 10-15 minutes. Sensitive to common disinfectant solutions (chloramine).
More than 100 species of wild and domestic birds (parrots, pigeons, chickens, etc.), as well as white mice, rats, guinea pigs, rabbits, and monkeys are very susceptible to the causative agent of ornithosis. Various strains of Chl.psittaci cause psittacosis, ornithosis, pneumonia in calves, sheep, goats, pigs, horses; polyarthritis in sheep, calves, pigs; placentitis and abortion in calves and sheep; enteritis in calves; conjunctivitis in guinea pigs, calves and sheep; encephalitis in marsupial rats and encephalomyelitis in calves. In parrots, the disease is characterized by runny nose, enteritis, debilitating diarrhea and is usually fatal. Diseases are seen in South America, Australia and other countries.
The pathogen that has entered the human body enters the bloodstream and causes bacteremia, which continues in | for a week, sometimes longer. In the tissues and organs of I, the pathogen goes through complex cycles that cause a violation of cellular metabolism, the development of intoxication and allergies. Ornithosis is characterized by the occurrence of a pneumonic focus without shortness of breath, cough and pain in chest. At the height of the disease x-ray examination the picture of regional lobular bronchopneumonia comes to light; resorption of exudate occurs slowly.
Sources of infection are birds (sick or carriers), domestic and wild pigeons, ducks, chickens, turkeys. Adult birds recover, young birds die in a large percentage of cases. The causative agent is excreted with excrement, from which healthy birds and people become infected. Infection of animals is possible in utero, through sexual contact and the bite of blood-sucking insects.
A person usually becomes infected by aerogenic by inhalation of infected dust or fluff, as well as when cutting birds, cleaning cages and caring for a bird, which is accompanied by contamination of the hands and contact with the pathogen on the mucous membranes. The possibility of infection from sick people by airborne droplets is not ruled out.
Immunity after the transfer of the disease is relative and short-lived. Recurrent illnesses have been noted, especially among laboratory workers. The body's defense mechanism is associated with the presence of antibodies.
Laboratory diagnostics. The causative agent is found in the first days of the disease in sputum and blood. In the blood, it persists until the 5-7th day, in sputum, until the 21st day of illness; the maximum duration of chlamydia excretion with sputum was noted for 8 years. When examining the material of the autopsy, the microorganism was isolated from the tissue of the lung, spleen, and exudate. To recognize ornithosis, microscopy is used, the complement fixation reaction with paired sera (at the beginning and at the end of the disease).
Chlamydia can be isolated from the blood and sputum of sick people by intracerebral infection of white mice. The causative agent can be detected in smears from the spleen, liver and brain sections of experimental animals infected by the intraperitoneal method. Isolation of the pathogen is also possible when chicken embryos are infected in the yolk sac. Good result gives an allergic test with ornithine and the fluorescence method.
Treatment. Tetracyclines, streptomycin are prescribed; in chronic forms, vaccine therapy is recommended.
Prevention. It is achieved by successive measures: early diagnosis, isolation and hospitalization of patients in infectious diseases hospitals (in separate wards or boxes). Service personnel should wear masks and regularly disinfect their hands with a 0.5% chloramine solution.
Chlamydia (Chlamydia) -- small gram-negative coccal bacteria, 250-1500 nm in size (0.25-1 microns). They have all the main features of bacteria: they contain two types of nucleic acids (DNA and RNA), ribosomes, muramic acid (a component of the cell wall of gram-negative bacteria), multiply by binary fission and are sensitive to some antibiotics.
In 1966, at the 9th International Congress of Microbiologists, chlamydia was excluded from the class of viruses.
Taxonomy
All chlamydia are grouped in order Chlamydiaceae, genus Chlamydia, the latter includes four types:
- Chlamydia trachomatis (Chlamydia trachomatis).
- Chlamydia psittaci.
- Chlamydia pneumonia.
- Chlamydia pecorum.
- Chlamydia psittaci- causes atypical pneumonia, encephalomyocarditis, arthritis, pyelonephritis in humans.
- Chlamydia pecorum described recently, isolated from sheep, cattle. Has a resemblance to Chlamydia psittaci. The role in the pathogenesis of human diseases is unknown.
- Chlamydia pneumoniae causes acute respiratory infections and a mild form of pneumonia in adults.
- View Chlamydia trachomatis found only in humans, 18 antigenic variants (serotypes) have been identified in it.
Serotypes A, B, C are the causative agents of trachoma. Carriers are insects, the main route of infection is the ingress of an infectious agent by rubbing into the area of \u200b\u200bthe mucous membrane of the eye. The scars formed as a result of the development of the infectious process lead to loss of vision. Serotypes L1-L3 multiply in lymphoid tissue and are the causative agents of the tropical venereal disease Lymphogranuloma venerum. In the case of serotypes from D to K, infection occurs through sexual contact, much less often through rubbing, a newborn becomes infected during childbirth from an infected mother.
Physiology and pathogenesis
The life cycle of chlamydia differs significantly from that of bacteria.
Chlamydia exist in two forms, differing in morphological and biological properties. The highly infectious, spore-like, extracellular form is the elementary body (ET), and the vegetative, reproducing, intracellular form is the reticular body (RT).
ET has the form of a sphere with a diameter of 0.15-0.2 microns. RT has the structure of typical gram-negative bacteria about 1 µm in size (See fig. 1.). EBs contain more disulfide bonds, which allows them to resist osmotic pressure.
The first stage of the infectious process is the adsorption of ET on the plasma membrane of a sensitive host cell. An important role at this stage is played by electrostatic forces. The introduction of chlamydia occurs by endocytosis. Invagination of the plasmalemma region with adsorbed ET occurs into the cytoplasm with the formation of a phagocytic vacuole. This phase takes 7-10 hours. After that, already in the cell, within 6-8 hours, the ET is reorganized into a vegetative form - a reticular body capable of growth and division. It is at this phase that the course use of antibacterial drugs is effective, since ET is not sensitive to them.
Reproduction of chlamydia leads to the formation of inclusions, known as Provachek bodies. Within 18-24 hours of development, they are localized in the cytoplasmic vesicle formed from the membrane of the host cell. An inclusion may contain from 100 to 500 chlamydia. Stopping the process at this stage leads to the persistence of chlamydial infection. Then the process of maturation of reticular bodies begins through transitional (intermediate) bodies during 36-42 hours of development in the next generation ET. The full reproduction cycle of chlamydia is 48-72 hours and ends with the destruction of the affected cell, in the event of unfavorable metabolic conditions for chlamydia, this process can be delayed for a longer period.
Chlamydia can be released from the infected cell through the narrow rim of the cytoplasm. In this case, the cell can remain viable, this can explain the asymptomatic course of chlamydial infection.
The protective reaction at the initial stage of infection is carried out by polymorphonuclear lymphocytes. Polyclonal activation of B-lymphocytes plays a significant role in the protection of the body. In the blood serum and secretory fluids in chlamydia, a significant amount of immunoglobulins IgG, IgM, IgA is found. However, the leading role in protection against chlamydial infection is occupied by T-helpers, which activate the phagocytic activity of macrophages.
Ultrastructure
The use of ultrastructural analysis methods made it possible to prove the possibility of chlamydia persistence in epithelial cells and fibroblasts of infected mucous membranes. Chlamydia are absorbed by peripheral monocytes and spread in the body, monocytes settle in the tissues and turn into tissue macrophages (in the joints, in the vessels, in the region of the heart). Tissue macrophages can remain viable for several months, while being a powerful antigenic stimulator, leading to the formation of fibrous granulomas in healthy tissue. Chlamydia or their fragments can be released from cells and cause the formation of specific antibodies, regardless of whether the chlamydial antigen is detected at the site of infection.
The structure of the cell wall of chlamydia corresponds to general principle construction of gram-negative bacteria (Fig. 2). It consists of an inner cytoplasmic and an outer membrane (both are double, providing strength to the cell wall). The antigenic properties of chlamydia are determined by the inner membrane, which is represented by lipopolysaccharides. The so-called outer membrane proteins (OMP) are integrated into it. The Major Outer Membrane Protein (MOMP) accounts for 60% of the total protein. The remaining antigenic structure is represented by proteins of the outer membrane of the second type - OMP-2.
Antigens
All chlamydia have a common group, genus-specific antigen (lipopolysaccharide complex, the reactive half of which is 2-keto-3-deoxyoctanoic acid), which is used in the diagnosis of the disease by immunofluorescent methods with specific antibodies.
The MOMP and OMP-2 proteins contain species- and serotype-specific epitopes. However, they also contain regions with high similarity among species (genus-specific epitopes), which leads to the possibility of cross-reactions. Basic protein cell membrane and other cysteine-rich proteins are linked by disulfide bonds. Five genes of disulfide-linked isomerases have been found, possibly playing a role in the restructuring of cysteine-rich proteins during the differentiation of elementary bodies into reticular ones. At Chl. trachomatis 9 genes encoding surface membrane proteins, y Chlamydia pneumonia–18.
Table 1. Chlamydia antigens (according to Mardh P., 1990)
Genetics
In 1998, Stephens et. al. announced genome sequencing Chlamydia trachomatis. The chlamydia genome is small and makes up no more than 15% of the E. coli genome. It consists of a chromosome containing 1042519 base pairs (58.7%) and a plasmid containing 7493 base pairs.
The analysis of the genome made it possible to isolate 894 genes encoding various proteins. The similarity with previously studied proteins of other bacteria made it possible to determine the functional purpose of 604 (68%) encoded proteins. 35 (4%) proteins were similar to proteins found in other bacteria. In the remaining 255 (28%) proteins, the sequences were not similar to those previously studied. Protein sequence analysis showed that 256 (29%) chlamydial proteins clustered into 58 families within the genome, similar to the grouping of proteins in small genome bacteria such as mycoplasmas and haemophilus influenzae.
(0.2–1.5 μm), gram-negative, obligate intracellular parasites. For their inability to synthesize their own high-energy compounds (they develop from the energy-rich compounds of the host cell), they are sometimes called "energy parasites." include one family, one genus with two species–Chlamydia trachomatis- the causative agent of trachoma and Ch. psittaci- pathogen ornithoses.
(Source: "Microbiology: glossary of terms", Firsov N.N., M: Bustard, 2006)
Chlamydia(Source: Glossary of Microbiology Terms)
See what "chlamydia" is in other dictionaries:
Chlamydia Chlamydia trachomatis Scientific classification Kingdom: Bacteria ... Wikipedia
- (Chlamydiales), an order of bacteria. Coccoid microorganisms (diam. 0.2 1.5 microns) with a characteristic obligate intracellular mode of reproduction. Includes seven. (Chlamydiaceae) with unity, genus and 2 species (Chlamydia trachomatis and C. psittaci). X.… … Biological encyclopedic Dictionary
- (Chlamydia, Ber; syn. miyagavanella) genus of microorganisms of the family. Chlamydiaceae (order Chlamydiales), uniting immobile coccus-like gram-negative intracellular parasites stained according to Romanovsky Giemsa; includes species that cause… Big Medical Dictionary
1. Classification: superkingdom Procaryota, kingdom Bacteria, section Scotobacteria, class Bacterias, order Chlamydiales, c. Chlamydiaceae, s. Chlamydia, c. C. trachomatis (1 biovar - trachoma, 2 biovars - venereal lymphogranuloma, 3 biovars - uro - and extragenital chlamydia), C. psitacci (ornithosis), C. pneumoniae.
2. Morphology: Gr-, small cocci, acapsular, without flagella, immobile. They are presented in two forms: elementary bodies of a spherical shape (outside a person) and reticular bodies (intracellularly).
4. Biological properties:
A) do not breed on artificial nutrient media
B) cultivated in the yolk sac of chicken embryos and in cell cultures
5. AG structure: group-specific lipoglycoprotein, species-specific AG.
6. Factors of pathogenicity and pathogenesis:
A) ornithosis:
Adhesion on receptors of epithelial cells of bronchi, bronchioles, lymphocytes → penetration and reproduction in cells → destruction of cells → penetration into intact cells → bacteremia → drift into parenchymal organs.
B) trachoma and venereal lymphogranuloma, urogenital chlamydia:
With trachoma and urogenital chlamydia: contact with the mucous membrane of the genitourinary organs, rectum, conjunctiva of the eyes → reproduction and accumulation in epithelial cells → release of toxins → local inflammatory processes (urethritis, conjunctivitis, proctitis) → spread through the mucous membranes → damage to the genitourinary organs.
With venereal lymphogranuloma 1) inflammation in the gate area is not expressed 2) the spread of MB is lymphogenous 3) mainly l. y. At the same time, chlamydia and their toxins can penetrate into the blood, causing an allergic restructuring of the body without the occurrence of secondary hematogenous foci in other organs.
7. Clinical manifestations:
A) ornithosis: phenomena of general intoxication, lung damage and a tendency to a protracted course with exacerbations.
B) trachoma: damage to the cornea and conjunctiva with the formation of follicles (trachomatous grains), in late stage- scarring of the conjunctiva and cartilage of the eyelids
C) venereal lymphogranuloma: damage mainly to the vulva, perineum and rectum
8. Immunity: GMO, KIO, HRT. Post-infection immunity is short-term and unstable. Cases of repeated diseases and reinfection are observed.
9. Epidemiology.
A) ornithosis: the source is birds. OPP - aerosol.
B) trachoma: source - patients with active and erased forms, with relapses of the disease, as well as carriers. OPV - through hands, clothes, towels, etc.
C) venereal lymphogranuloma, urogenital chlamydia: the source is a sick person or a carrier, OPV - sexual, sometimes contact-household.
10. Prevention: Vaccination is not applied.
11. Treatment: AB tetracycline group, erythromycin and rifampicin.
12. Diagnostics:
1. Bacterioscopic research method: detection of chlamydia, their morphological structures and antigens in the affected cells (clinical material).
Material for the study: scraping preparations from the mucous membranes of the urogenital tract (urethra, cervix, etc.) and other organs (conjunctiva, rectum, etc.) available for examination in extragenital forms.
A smear according to Romanovsky-Giemsa. Cytoplasmic inclusions of chlamydia (Halberstedter-Provachek bodies) contain large reticular bodies or small elementary bodies. RT and ET differ in color and internal structure from the cell nucleus and cytoplasm.
The method is characterized by relatively low sensitivity. The use of luminescent polyclonal and monoclonal antibodies to detect Chlamydia AG in cytoplasmic inclusions in scraping preparations of the urogenital tract significantly increases the sensitivity and specificity of the method. Both direct and indirect immunofluorescent methods are used. With fluorescent microscopy, chlamydia antigens are detected against a red or orange background of the cytoplasm of epithelial cells in the form of bright green intracellular inclusions. In terms of information content and sensitivity, it is inferior only to the bacteriological method.
When diagnosing ornithosis and other zoonotic chlamydia, the bacterioscopic method is not used.
2. Bacteriological research method: isolation of chlamydia from infectious material by infection of chicken embryos, laboratory animals or cell cultures, followed by indication of the pathogen.
Material for research: - the same as for bacterioscopy. With ornithosis - blood or sputum. Blood from a vein (not less than 5 ml) is examined in the first 7-10 days of the disease, sputum - up to the 14th day of the disease. To remove the accompanying microflora, antibiotics are added that do not act on chlamydia (streptomycin, nystatin, gentamicin). When a chicken embryo is infected, the test material is injected into the yolk sac of a 6-7-day-old developing embryo. Indication of chlamydia is carried out after 48-72 hours based on the detection of typical cytoplasmic inclusions containing elementary and reticular bodies (imprint smears from the yolk sacs of chicken embryos and (or) assessment of infected cells - Macchiavello stain, direct and indirect RIF).
When diagnosing ornithosis, in addition to cell cultures, it is possible to infect piboratory animals (into the brain or intraperitoneally).
3. Serological research method: antibodies are detected in blood serum, which is examined 2-3 times with an interval of 10-14 days, and secrets of the genital organs. For diagnosis, RSK, RPGA, RIF, ELISA are used. In urogenital chlamydia, titers of 1:32-1:64 are diagnostically significant in RIF. The most reliable is the increase in antibody titer by four or more times.
4. Allergological research method: setting skin-allergic tests. Used in the diagnosis of ornithosis with ornithosis allergen. The intradermal test becomes positive from the first days of the disease in most patients, remaining up to a year or more.
