The below mentioned article provides a study note on Chlamydial Infection.
Introduction to Chlamydial Infection:
The genus chlamydia includes organisms previously called as Psittacosis-Lymphogranuloma venereum, Trachoma group (PL T) organism. The generic name Bedsonia has also been used in recognition of Bedson; but by the rules of nomenclature chlamydiae has priority.
It is now clear that the chlamydiae are small prokaryotic that have evolved to a highly parasitic existence in the cytoplasm of cells. These organisms are small, non-motile, Gram-negative obligate intracellular parasites.
They occur in two forms:
Lipopolysaccharide (LPS) Genus specific genus specific genus specific:
(a) There is a small, 300 nm diameter form, which has a compact electron-dense nucleoid which is highly infectious, stable, extracellular form or elementary body.
(b) There is a large form, 800-1200 nm in diameter without a dense nucleoid, the ‘initial body’ which is intracellular, replicating form. The organisms grow in the cytoplasm of their host cells forming characteristic micro-colonies or inclusion bodies which are made up of a mixture of the larger and smaller cells. Both forms stain well with Castaneda or Giemsa stain.
Chlamydiae have 2 Subgroups—A, B:
Subgroup A has compact inclusions with a glycogen matrix. Subgroup B has no glycogen matrix. These two groups also differ in their susceptibility to sulphadiazine.
Chlamydial infection of man takes two main clinical forms:
(a) organism of psittacosis ornithosis causes respiratory illness with fever; and
(b) trachoma-inclusion conjunctivitis (TRIC)—Lympho-granuloma venereum (LGV) organism of sub group A causes the clinically quite dissimilar ocular, genital infection. TRIC-LGV subgroup A chlamydia contains a group of infections transmitted by contact—mainly sexual— in developed countries but also eye to eye in underdeveloped countries where trachoma is endemic.
LGV is more invasive; it starts as a small painless papula or ulcer (Lymphogranuloma chancre) on the external genitalia, or internally some 5 to 10 days after exposure. The infection spreads to the regional lymph nodes (inguinal, perirectal) with suppuration in many cases and sometimes a generalized infection with fever and rash, arthritis, conjunctivitis and meningoencephalitis.
In late stage of the disease chronic inflammation around lymphatic’s in the genital and rectal area leads to fibrosis with elephantiasis of the genitalia. Rectal structures are common in women and male homosexuals. The treatment of genital infections is by 21 days’ course of tetracycline, 250 mg, 4 times a day.
Pathogenicityof Chlamydial Infection:
Chlamydial infection in man occur in three forms:
(a) Febrile respiratory disease caused by C. pneumoniae and C. psittaci,
(b) Ocular, and
(c) Genital lesions caused by C. trachomatis.
Antigenic structure of Chlamydial Infection :
Chlamydiae have two types of antigens:
1. Heat-stable complement fixing antigen is a lipopolysaccharide protein complex similar to cell wall of Gram-negative bacteria. It can be extracted by deoxycholate, ethanol, chloroform.
2. Heat-labile antigen is a type-specific antigen left on cell wall after extraction of cell with trypsin or deoxycholate.
Genital Tract Infection:
Recently more interest was focused on chlamydia because of its involvement in genital tract infection, this infection was known since the first decade of this 20th century. Most of the ophthalmologists who worked on patient with ocular disease, traced the infection chain from the genital tract. In 1959, Chlamydiae were isolated from cervix and by 1964 they were recovered from men with urethritis and women with cervicitis.
LGV:
Usually, the inguinal lymph nodes of males are involved in LGV. Fistula or anogenital disease may occur in travellers (having sexual exposure) returning from South East Africa or Central America or South America. Diagnosis is not easy by physical examination but the serological test (CFT or micro- immuno-fluorescence test) may be useful.
Cultivation:
C. psittaci is the first to be propagated in mice by intra-peritoneal inoculation and in chick embryo and tissue cultures.
Resistance:
Chlamydiae are heat labile and are inactivated at 56°C within few minutes. They are susceptible to dilute solution of formalin and phenol N-acetyl-muramic acid is lacking in cell membrane.
Frei test—a delayed hypersensitivity skin test—is not useful as it was once, and is no longer available in United States.
Therapy:
Tetracycline or sulphonamides are not very much effective.
Erythromycin with full systemic doses is very useful in patients allergic to tetracyclines.