Chlamydiae are obligate intracellular parasites that cause disease in humans and animals. There are three main species: Chlamydia trachomatis, C. psittaci, and C. pneumoniae. C. trachomatis causes trachoma, inclusion conjunctivitis, and lymphogranuloma venereum. It has 15 serotypes and is transmitted sexually or from eye to eye. C. psittaci causes psittacosis in birds and ornithosis in humans via inhalation of bird droppings. C. pneumoniae is a common cause of respiratory infections in humans transmitted through coughing or sneezing. Chlamydiae have both RNA and DNA

1. CHLAMYDIAE- THE SILENTKILLER
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2. CLASSIFICATION
Class – Chlamydiae
Order – Chlamydiales
Family – Chlamydiaceae
Genus – chlamydia
Chlamydia species are classified into 3 groups :
Chlamydia trachomatis – Trachoma, Inclusion conjuctivitis, LGV
Chlamydia psittaci – Psittacosis, Ornithosis
Chlamydia pneumonia – Respiratory infections
• Chlamydia are a group of pathogens causing disease in humans and a wide variety
of animals.
• Chlamydia is a common sexually transmitted disease caused by bacteria.
• They are small obligate intracellular parasites ie.,they can grow only within cells..
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3. HISTORY
• Chlamydia affecting the eyes of humans was 1st described in ancient Chinese and
Egyptian manuscripts ( Written document)
• In 1907 , Halberstaedter and Von Prowazek observed Chlamydia in conjuctival
scrapings from experimentally infected orangutan.
• C.trachomatis was described in Egyptians.
• LGV was described in 8th century and 1st isolated in 1930s.
• In 1951, when the disease reported there were 10,764 cases in men and no number of
cases in women.
• Chlamydial isolates cultured in the yolk sac of embroyonating eggs were obtained from
human pneumonitis outbreak in late 1920s and early 1930s ,by the mid 20th century
isolates had been obtained from dozens of vertebrate species.
• Chlamydia 1st become recognised as a specific STI in1970s, but it took until 1988 for it
to become notifiable.
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4. Characteristics
• Contains both RNA and DNA
• Multiplies by binary fission
• Cannot genarate ATP – depends on host cell for energy
• Susceptible to antibacterial agents like ethanol,ether ,low
concentration of formalin
Morphology
• Chlamydia is a gram negative, coccobacilli,
spherical, non-motile
• It exists in 2 forms :
elimentary body and reticulate (initial) bodies
• Elementary bodies :-small, 200-300 nm in
diameter ,extracellular(outside a cell) infectious
and have rigid cell wall.
• Initial bodies :- large , 500-1000 nm in diameter,
intracellular ( inside cell) and have fragile (easily broken) cell wall.
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5. CULTURAL CHARACTERISTICS
• Cannot be grown in non-living media
• Grown in yolk sac of embroyonated eggs, animal, tissue culture
Staining – Giemsa and Castaneda stains
Elementary bodies – Stain red by acid stain
Initial bodies – Stain blue by basic stain.
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6. CHLAMYDIA TRACHOMITIS
• Causes various diseases like Trachoma, Inclusion conjuctivitis and LGV
• It has 15 serotypes( groups within a single species of microorganisms) from A to L3
• The sub group is sometimes referred as TRIC agents( Trachoma-Inclusion Conjuctivites) as
both diseases are similar in nature.
TRACHOMA
• Caused by C. trachomatis serotypes A,B,Ba,C
• Trachoma is a chronic keratoconjuctivites – formation of fibrous tissue in conjuctiva and
cornea
• Ancient disease in India, Egypt, Middle East, North Africa and Russia
• It is the major cause of blindness worldwide
Incubation period- variable and influenced by dose of infection
Transmission:- Eye to eye, fingers ,fomites, flies, dust,etc
Laboratory diagnosis:- Findiing inclusion bodies in the smear by Giemsa staining
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7. Culture
Embryonated eggs :-
• Most commonly used Culture for isolating Chlamydia
• 6-8 days old chick embryo yolk sacs are used
• All known strains of Chlamydia will infect embryo
• Sample should be treated with streptomycin or polymixin B before inoculation.
• The eggs showing death of embryos within 3-7 days after inoculation, yolk sac is taken
and stained.
• Examined for the presence of elementary bodies or inclusion bodies.
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8. In Mice :-
• The specimen is inoculated intracerebrally into mice
• Examined for the development of the disease
• The brain is then removed from the sick mice
• Examined for the presence of inclusion bodies
Irradiated McCoy cell culture is more useful for the isolation of Chlamydia
Treatment – Sulfanamides and Tetracycline
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9. INCLUSION CONJUCTIVITIS
• Caused by C.trachomitis serotypes D to K
• Similar to trachoma but milder condition
• Primary habitat in human genital tract than eye
Neonatal form:- “Inclusion Blenorrhoea” occurs during delivery of newborn and
symptoms appears after 5-12 days after birth
Adult form :- “Swimming pool conjuctivitis” infects by bathing in contaminated pool with
genital secretions
Transmission:- sexual contact, sometimes through eye to eye
Diagnosis:- sample is examined for inclusion bodies
Culture :- embryonated eggs
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10. LYMPHOGRANULUM VENERUM ( LGV)
• sexually transmitted disease
• Caused by C.trachomatis serotypes L1,L2, L3
Inncubation period :- 3 days to 5 weeks
• 1° stage- small painless lessions on genetalia appears
• 2°stage- 2 weeks later it spread to draining lymph nodes
• 3° stage- Chronic and last for years, scarring, lymphatic block, elephantasis of
genetalia is seen
Diagnosis :- staining, isolation of organisms,CFT, Frei test ( skin test) mostly used
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11. Frei’s Test :-
• Also called as “skin test”
• 0.1ml antigen is injected intradermally into forearm
• The antigen is prepared either by
a] heating diluted bubo pus to 60°c for 3 hours to destroy infectivity
b] growing organisms in yolk sac and using purified and phenolised elementary bodies
• After 48 hours patient is examined for induration
• Positive reaction – development of induration of 7mm or more is seen, after 2-6 weeks of
infection
Culture :- embryonated eggs, mice
Treatment :- varies with stage of disease, Sulphadiazine is the drug of choice, Tetracycline
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12. CHLAMYDIA PSITTACI
It causes psittacosis and ornithosis
Psittacosis
• Disease of parrots and parakeets
• Caused by C. psittaci
• Similar infections of many other kinds of birds including pigeons,ducks,turkey,
and gulls are collectively known as Ornithosis.
Transmission in man :-
Inhaling bird droppings or nasal discharge
Incubation period :- 7-10days
Symptoms :-
Fever, severe headache, sore throat
In 2nd week, infection spread through respiratory tract to blood and skin.
Liver, spleen, heart and kidney may become enlarged and congested which leads
various diseases like arthritis etc.
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13. Diagnosis :- CFT, difficult diagnosis since
symptoms similar to other respiratory
infections.
Culture :- embryonated eggs, mice
Treatment :- Tetracycline
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14. CHLAMYDIA PNEUMONIA
• It causes common respiratory disease in older children and adults
• 1st recognised as respiratory pathogen
• Reinfection are common
Transmission :- Droplets while coughing or sneezing
Symptoms :- Mild respiratory infections including acute pneumonia, bronchitis,
cough, little or no fever, sinusitis and pharyngitis
Diagnosis :- direct immunofluorescence, sample of sputum ,swab from nose or
throat is Cultured
Treatment :- Azithromycin/Clarithromycin (macrolides) Erythromycin, Tetracycline
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15. Chlamydia pneumonia in lung cell under TEM
Chlamydia pneumonia
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16. References :-
Textbook of medical microbiology– H.L Chopra
The short textbook of medical microbiology 3rd edition by Satish Gupte
The short textbook of medical microbiology 5th edition
The short textbook of medical microbiology 8th edition by Satish Gupte
Introduction to medical microbiology by R.Ananthanarayana
Medical microbiology by C.G.A.Thomas
Microbes and diseases of man
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17. THANK YOU
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