Chlamydia is an obligate intracellular bacterium that can cause several diseases in humans. It has a unique life cycle alternating between two forms - the infectious elementary body and the dividing reticulate body. C. trachomatis is the most common species and can cause trachoma, sexually transmitted diseases like urethritis and cervicitis. C. psittaci causes psittacosis transmitted from birds while C. pneumoniae causes atypical pneumonia. Diagnosis involves culture or serology while treatment uses tetracycylines or macrolides. Prevention focuses on abstinence, barrier methods and controlling infection in birds.

1. Chlamydia
Faculty: Dr. Tariq Mahmud Tariq
Asst. Professor Microbiology
Email: tariq.fmic@yahoo.com

2. General Characteristics
 Very small
 Non-motile
 True bacteria
 Coccoid in shape
 Obligate intracellular
o Lack several biosynthetic pathways
o No energy pathways, totally depend
on cell for ATP

3. General Characteristics (cont’d)
Structures
 DNA genome & one plasmid
 Elementary body (EB)
o Extracellular, Infectious particle
o Contain RNA polymerase & Ribosomes
 Reticulate body (RB)
o Develop into a large cytoplasmic inclusion

4. 1. The extracellular, EB enters epithelial cell
2. EB changes into a RB
3. RB divides by binary fission
4. The daughter RBs change into EBs &
grow into a large cytoplasmic inclusion
body, typical of chlamydial infections
5. Newly formed EBs are released from the
epithelial cell to infect new epithelial cells
Life cycle of Chlamydia

5. Life cycle of Chlamydia

6. Cytoplasmic inclusion body seen in Chlamydial infection

7.  C. trachomatis
 C. psittaci
 C. pneumoniae (TWAR)
Important species of Chlamydia

8. Direct Contact:
 C. trachomatis, causative agent of:
1) Trachoma
2) NGU
3) Inclusion Conjunctivitis
4) LV
Respiratory Route:
 C. pneumoniae: Causes Pneumonia
 C. psittaci: Causes Pneumonia
How Chlamydia Spread?

9. Chlamydial Diseases

10. Chlamydial Diseases

11. C. trachomatis
Epidemiology
 Worldwide
 Prevalent in Africa & Asia
Modes of Transmission
 Inoculation/STDs
 Fingers or fomites
 Infected birth canal

12. C. trachomatis Epidemiology (cont’d)
1. Eye Infections (caused by A,B,Ba,C types)
 Trachoma (severe form)
 Inclusion conjunctivitis (milder form)
2. STDs (caused by D-K types)
 Transmitted by anal, oral, vaginal sex
 Men: NGU, Epididymitis, Proctitis
 Female: Cervicitis, Salpingitis, Proctitis
o ~45% of infections occur in teenage girls
o ~ 90% of infected women are asymptomatic
 Co-infection by N. gonorrhoeae in ~50% of cases

13. C. Trachomatis Epidemiology (cont’d)
 STDs (caused by L1,L2,L3 types):
• Lymphogranuloma venereum (LV)
o Usually men
o Different from strains that cause trachoma
o Latent infection
o Can be transmitted to eyes
 Exposure during birth:
• Neonatal conjunctivitis

14. C. trachomatis Pathogenesis
 Attachment to conjunctival epithelial cells
 Subepithelial infiltration by lymphocytes
 Damage induces invasion by fibroblasts &
blood vessels
 Cornea becomes vascularized and clouded
 Eyelids become scarred & malformed
o Trichiasis: Abnormal inward growth of eyelashes,
leads to cornea opacification & blindness

15.  Off-white vaginal discharge
 Dysuria (pain during urination)
 Dyspareunia (painful intercourse)
 Constant abdominal pain
 Spotting between periods
 Cervicitis: Inflammation of the cervix
 Salpingitis: Inflammation of fallopian tubes
STD Diagnosis in Female

16.  Cervicitis with a mucopurulent or purulent discharge
containing an increased number of polymorphonuclear
leukocytes (PMNs)
 Important causes of cervicitis include chlamydia and
gonorrhea (though these infections are frequently
asymptomatic in women)
STD Diagnosis in Female (cont’d)

17.  Non-gonococcal urethritis (NGU)
o The patient may present with urethral itching and a
clear urethral discharge after unprotected
intercourse.
o Symptoms presenting more than one week after
unprotected sex tend to be non-gonococcal in nature
STD Diagnosis in Male

18.  LV (Lymphogranuloma venereum)
o Also known as:
• Lymphogranuloma inguinale
• Sixth venereal disease
• Tropical bubo
o Infection of the lymph tissue in genital area
o Both males & females can be infected
Diagnosis of LV

19. Diagnosis of LV (cont’d)
 A small, painless sore similar to a blister occur at
the point where the bacterium entered the body
(penis or vagina) that often goes unnoticed
 The infection then spreads to the lymph nodes in
the groin area & the surrounding tissue, where it
causes painful swelling
 Lymph nodes closest to the infection continue to
swell until a pus-filled bulge (bubo) is formed
 Discharge from the penis or vagina from 3-30
days after exposure

20. Diagnosis of LV (cont’d)
The buboes can:
 Grow very big, until the covering
skin turns blue
 Open through the skin, drain
continuously & remain open
(about 30% of cases)
 Can become infected by other
bacteria

21. C. trachomatis - Lab Diagnosis
1. Cytology for intracytoplasmic inclusions
2. Direct Fluorescent Antibody (DFA)
3. Enzyme immunoassay (EIA)
4. PCR

22. C. trachomatis complications in Female
1. Ectopic Pregnancy: Tubal pregnancy can
be fatal
2. Pelvic inflammatory disease (PID)
 Infertility
 Chronic pain
 Death
3. Sterility
4. Reiter’s Syndrome: An autoimmune
syndrome associated with HLA-B27; triad of
conjunctivitis, polyarthritis & genital inflammation

23. C. trachomatis complications in Male
1. Non-gonococcal urethritis (NGU)
2. Epididymitis: Inflammation of testicles
3. Prostatitis: Infection of prostate gland
4. Reiter’s Syndrome:
5. Sterility

24. C. trachomatis - Treatment
1. Azithromycin
2. Clindamycin
3. Doxycycline
4. Erythromycin
5. Ofloxacin
6. Rifampicin

25. C. trachomatis - Prevention & Control
 No vaccine
 Abstinence
 Condoms or diaphragms
 Regular tests for STD

26. Chlamydia psittaci
 C. psittaci is the causative agent of
psittacosis (parrot fever)
 Although the disease was first transmitted
by parrots, the natural reservoir can be
any species of bird
 Thus, the disease has also been called
ornithosis [from the Greek word for 'bird‘]
 Human infection is respiratory

27. C. psittaci Pathogenesis
 Infection is by inhalation of bacteria from infected
birds or their droppings
 Person-to-person transmission is rare
 From the lungs the bacteria enter the bloodstream
and are transported to the liver & spleen
 The bacteria replicate at these sites where they
produce focal areas of necrosis
 A lymphocytic inflammatory response in the
alveoli & interstitial spaces leads to edema,
macrophage infiltration, necrosis & hemorrhage
 Mucus plugs may develop in the alveoli causing
cyanosis & anoxia

28. C. Psittaci (cont’d)
Lab Diagnosis:
 Based on serological tests
 A 4-fold titer rise in paired samples is
indicative of infection
Treatment & Prevention:
 Tetracycline or erythromycin
 Control of infection in birds by feeding
of antibiotic supplemented food
 No vaccine is available

29. Chlamydia pneumoniae
The organism was originally called the TWAR
strain from the names of the two original isolates:
 Taiwan (TW-183) &
 An acute respiratory isolate designated AR-39
 C. pneumoniae is the causative agent of an
atypical pneumonia (walking pneumonia) like
that caused by Mycoplasma pneumoniae

30. C. pneumoniae (cont’d)
Potential link to Atherosclerosis:
 There is a high incidence of C. pneumoniae
infection in the patients with atherosclerosis
Laboratory Diagnosis:
 Culture is difficult so serological tests are requested
 A 4-fold rise in titer in paired samples is diagnostic
Treatment & Prevention
 Tetracycline & erythromycin are antibiotics of choice
 No vaccine is available