CHLAMYDAE

          Chlamydiae are obligate intracellular bacterial parasites of humans, animals and birds with tropism for squamous epithelial cells and macrophages of the respiratory and gastrointestinal tracts. Based on the human disease they are known to cause, they are called psittacosis-lymphogranuloma-trachoma (PLT) viruses or PLT agents.

            Due to their inability to grow in cell free media, they were initially considered to be viruses. However, they differ from viruses in many respects. They posses both DNA and RNA, have cell walls and ribosomes, replicate by binary fission and are susceptible to the usual antibiotics and chemotherapeutic agents. They are therefore accepted as bacteria.

            The genus Chlamydia contains four species – C. trachomatis, C. psittaci, C. pneumoniae and C. pecorum.

1. GENUS: CHLAMYDIA TRACHOMATIS

            Chlamydia trachomatis is a leading cause of ocular and genital infections worldwide.

            (a) Trachoma:- Trachoma is a chronic keratoconjunctivitis characterized by follicular hypertrophy, papillary hyperplasia, pannus formation and in the late stages cicatrisation. The name trachoma is derived from the Greek trakhus (rough) referring to the roughness of the conjunctiva in the disease.

            Infection of the disease is transmitted from eye to eye by fingers or fomites. Flies may transmit the infection mechanically. It may also be carried by dust, in which case infection may be facilitated by minor abrasions caused by duct particles.

            Inclusions Conjunctivitis - Inclusion conjunctivitis is a sexually transmitted inflammation disease of the conjunctiva (the membrane that lines the eyelids and covers the white part, or sclera, of the eyeball) by Chlamydia trachomatis. This disease affects four of 1,000 (0.4%) live births. Approximately half of the infants born to untreated infected mothers will develop the disease.

            Inclusion conjunctivitis in the newborn results from passage through an infected birth canal and develops 5-14 days after birth. Both eyelids and conjunctivae are swollen. There may be a discharge of pus from the eyes.

            Most instances of adult inclusion conjunctivitis result from exposure to infected genital secretions. It is transmitted to the eye by fingers and occasionally by the water in swimming pools, poorly chlorinated hot tubs, or by sharing makeup. In adult inclusion conjunctivitis, one eye is usually involved, with a stringy discharge of mucus and pus. There may be little bumps called follicles inside the lower eyelid and the eye is red. Occasionally, the condition damages the cornea, causing cloudy areas and a growth of new blood vessels (neovascularization).

            Treatment in the newborn consists of administration of tetracycline ointment to the conjunctiva and erythromycin orally or through intravenous therapy for fourteen days. The mother should be treated for cervicitis and the father for urethritis, even if they do not have symptoms of these diseases.

            In adults, tetracycline ointment or drops should be applied to the conjunctiva and oral tetracycline, amoxacillin, or erythromycin should be taken for three weeks, or doxycycline for one week. Patients should have weekly checkups so the doctor can monitor the healing. Oral tetracycline should not be administered to children whose permanent teeth have not erupted. It should also not be given to nursing or pregnant women.

            Infant Pneumonia – Chlamydia trachomatis can cause pneumonia in infants, usually around 4-6 weeks of age. Characteristically, they develop prominent respiratory symptoms with cough and wheezing but fever and toxicity are minimal. Conjunctivitis often precedes pneumonia. They show eosinophilia and high titre IgM antibodies to the infecting serovar. Immune response is believed to have a role in the pathogenesis of this condition.

            (b) Genital Infection:- Chlamydia trachomatis cause two types of genital infections – miscellaneous urogenital syndrome caused by the oculogenital serotypes D to K, collectively referred to as ‘genital chlamydiasis’, and LGV caused by serotypes L1, L2 and L3.

            Lymphogranuloma venereum is a sexually transmitted disease, characterized by suppurative inguinal adenitis. It is caused by LGV serovars of C. trachomatis L1, L2 and L3 – most commonly L2.

2. GENUS: CHLAMYDIA PSITTACI

             (c) Psittacosis:- Psittacosis is a disease of parrot and other psittacine birds, transmissible to human beings. Infection in birds is usually subclinical leading to a carrier state. The disease may be precipitated by caging or overcrowing and is manifested as diarrhea, mucopurulent respiratory discharge and emaciation. Chlamydia are shed in the droppings or nasal discharge and aerosols are liberated. Human infections are mostly occupational, as in poultry workers, pigeon farmers, petshop owners, bird fanciers and veterinarians. Infection occurs by inhalation.

3. GENUS: CHLAMYDIA PNEUMONIAE

            (d) Respiratory Disease:- It is a common respiratory disease in older children and adults caused by Chlamydia pneumonia. Its clinical spectrum includes pharyngitis, sinusitis, bronchitis and pneumonia, which resembles Mycoplasma pneumonia.       

            The Chlamydia are transmitted from human to human without any avian or animal hosts. Outbreaks have been reported in closed communities. Primary infections occur in young children. Reinfections are common.

************