Chlamydiae are obligate intracellular pathogens, with three key human species: Chlamydia trachomatis, Chlamydophila psittaci, and Chlamydophila pneumoniae, each causing different diseases like STDs and pneumonia. C. trachomatis, the most common STD pathogen, presents in multiple serotypes associated with conditions such as trachoma and lymphogranuloma venereum. Diagnosis typically involves detecting intracytoplasmic inclusion bodies or antigens in specimens, with treatment options including tetracyclines and macrolides.

1. CHLAMYDIA

2. General features:
• Chlamydiae are obligate intracellular organisms
• Depend on the host cell for energy (ATP).
• Therefore can grow only inside host cells.
• Chlamydiae are small, round-to-ovoid organisms
that vary in size during different stages of their
life cycle

3. • There are three important human pathogens:
1. Chlamydia trachomatis
2. Chlamydophila psittaci
3. Chlamydophila pneumoniae.
• C. pneumoniae and C. psittaci are different
molecularly from C. trachomatis.

4. • Therefore have been placed into a new genus
called Chlamydophila.
• Thus Chlamydophila pneumoniae and
Chlamydophila psittaci.
• But still known as Chlamydia pneumoniae and
Chlamydia psittaci

5. Structure:
• They have a rigid cell wall but do not have a
typical peptidoglycan layer.
• C. trachomatis is the most common cause of
STDs.
• Chlamydia pneumoniae causes atypical
pneumonia.
• C. psittaci causes psittacosis ( mainly disease of
birds)

6. Pathogenesis:
• Chlamydiae have a unique life cycle, with distinct
infectious and reproductive forms.
• The infectious form is called elementary body.
• It is a tiny, condensed structure that is
extracellular and initiates an infection.
• The elementary body enters by phagocytosis into
susceptible host cells.

7. • The elementary body is present in phagosome
inside the host cell.
• Inside the cell, the elementary body prevents
fusion of the phagosome and lysosome.
• The particle reorganizes over the next 8 hours
into a larger, noninfectious reticulate body.
• The phagosome now becomes a larger structure.

9. • This vacoule/larger phagosome is called
inclusion body.
• Reticulate body divides repeatedly by binary
fission.
• After 48 hours, multiplication ceases, and
reticulate bodies condense to become new
infectious elementary bodies.
• This whole process causes host cell death and
release of elementary bodies.

12. • C. psittaci and C. pneumoniae each have 1
immunotype, whereas C. trachomatis has at least 15.
• Laboratory identification
1. Chlamydiae are not seen by Gram stain
• Can be visualized under light microscope by
Giemsa stain.
2. Direct immunofluorescence is also a common and
useful procedure

13. Chlamydia trachomatis
Inclusion
Nucleus of cell

14. CHLAMYDIA TRACHOMATIS
• C. trachomatis has 15 serotypes, which are related
to different diseases.
• C. trachomatis infects only humans.
• Mainly causes NGU (Non Gonococcal Urethritis)
and Trachoma.
• Usually transmitted by close personal contact.

15. • Pathogenesis & Clinical Findings:
• C. trachomatis exists in more than 15
immunotypes (A–L).
A. Trachoma:
• Types A, B, and C cause trachoma, a chronic
keratoconjunctivitis.
• Endemic in Africa and Asia.

16. • Previously known as Egyptian ophthalmia.
• Primarily affects the superficial epithelium of
conjunctiva and cornea simultaneously.
• The word 'trachoma' ('rough' )comes from the
Greek word because surface appearance of the
conjunctiva in chronic trachoma is rough or
granular.

17. • It is still one of the leading causes of preventable
blindness in the world.
• Because of persistent /repeated infection over
several years leads to scarring causing permanent
opacities of the cornea and distortion of eyelids.

18. • Trachoma can be further divided into
1. Blinding trachoma
2. Non blinding trachoma
3. Paratrachoma
1. Blinding trachoma.
• It is caused by serotypes A, B, Ba and C of
Chlamydia trachomatis.

19. • It is associated with secondary bacterial infection.
• It is transmitted from eye to eye by transfer of
ocular discharge.
• There is mucopurulent conjunctivtis
2. Non-blinding trachoma.
• It is also caused by serotypes A, B, Ba, and C; but is
not associated with secondary bacterial infections.

20. • It is a mild form of disease with limited
transmission due to improved hygiene.
• Symptoms are minimal and include mild foreign
body sensation in the eyes.
3. Paratrachoma.
• It is caused by serotypes D to K and L1,L2 and L3
as well.
• It spreads from genitals to eye.

21. • It manifests as either
a. Adult inclusion conjunctivitis or
b. Chlamydial ophthalmia neonatorum.
• Trachoma is a chronic infection.

22. Follicular
conujnctivitis
Intense
follicular
inflammation

23. Tarsal conjunctival scarring
Blinding trachoma with entropion and
trichiasis

24. B. Genital infections:
• Types D–K cause genital tract infections.
• In men, it causes NGU, which may progress to
epididymitis or prostatitis.
• In women it causes cervicitis which may progress to
salpingitis and pelvic inflammatory disease (PID).
• Repeated episodes of salpingitis or PID can result in
infertility or ectopic pregnancy.

25. a. Neonatal conjunctivitis (chlamydial
ophthalmia neonatorum) :
• In infants born to genitally infected women.
b. Inclusion conjunctivitis:
• Conjunctivitis also occurs in adults due to transfer of
organisms from the genitals to the eye.
• Patients with genital infections have a high chance

26. of developing Reiter's syndrome (urethritis,
arthritis and uveitis)
• C. trachomatis directed antibodies cross react.
c. Lymphogranuloma venereum:
• C. trachomatis serotypes L1, L2, and L3 cause LGV
• More invasive STD.
• It is uncommon in the United States but endemic
in Asia, Africa, and South America.

27. • Formation of transient papules on genitalia,
followed in 1 to 2 months by painful swelling of
inguinal and perirectal lymph nodes.
• The affected lymph nodes suppurate and then
chronic inflammation and fibrosis leads to
blockage of regional lymphatic drainage.

28. • Lab diagnosis:
1. Infections can be diagnosed
by demonstrating typical
intracytoplasmic inclusion
bodies.
• For detection of inclusion
bodies, fluorescent antibody,
iodine staining and Giemsa
staining techniques are used.

29. Inclusion body

30. 2. Chlamydial antigens can also be detected in
exudates or urine by ELISA.
• PCR based test using the patient's urine can also
be used to diagnose chlamydial STD.
3. Cell culture:
• In this case suspected specimen is added to
special cells, which are then cultured in
laboratory.

31. • The infected cells are stained with iodine to
detect the glycogen-positive inclusions.
• The presence of chlamydial inclusions can be
demonstrated after 2 to 7 days of incubation.

32. Chlamydia trachomatis on cell culture
Inclusion
Nucleus of cell

34. • Treatment:
• All chlamydiae are susceptible to tetracyclines,
(doxycyline), and macrolides (erythromycin and
azithromycin).
• The drug of choice for STDs is azithromycin.
• The drug of choice for chlamydial ophthalmia
neonatorum is erythromycin.

35. • Because of co-infection with gonococci, any
patient with a diagnosis of genital infections
should also be treated for Gonorrhoea and vice
versa.
• Prevention:
• There is no vaccine against any chlamydial
disease.
• So other preventive measures should be used.