Chlamydiae are obligate intracellular bacteria that cause diseases like trachoma, pneumonia, and psittacosis in humans. They exist in two forms - the infectious elementary body and replicating reticulate body. Chlamydiae undergo a biphasic life cycle inside host cells, starting with endocytosis of the elementary body which then differentiates into a reticulate body and undergoes cell division before re-differentiating into more elementary bodies. Chlamydia trachomatis causes ocular infections like trachoma and genital infections, while Chlamydophila psittaci causes psittacosis. Laboratory diagnosis involves microscopy, antigen detection, nucleic acid amplification tests, and cell culture. Treatment

1. Chlamydiae

2. Chlamydiae are obligate intracellular bacteria. It does not grow in cell free
media.
They cause a spectrum of diseases in man such as Trachoma,
lymphogranuloma venereum (LGV), conjunctivitis, pneumonia and psittacosis.
Chlamydiae are classified into following groups:
Group A:
1. It causes: a. Lymphogranuloma venereum. b. Trachoma. c. Inclusion
conjunctivitis.
2. It forms compact inclusion with glycogen matrix.
Group B:
1. It causes: a. Psittacossis. b. Ornithosis.
2. It produces diffuse inclusion without glycogen matrix.

3. Chlamydiae are Bacteria, Not Viruses
Chlamydiae were once thought to be viruses,However, they are now
confirmed to be bacteria.
Properties similar to virus properties similar to that of bacteria
They are obligately intracellular. Possess both DNA and RNA.
They cannot grow in cell free culture media Cell wall similar to gram negative bacteria
Filterable that is they are small enough to
pass through bacterial filter
Capable of synthesising their on nucleic
acid, lipid and protein

4. Life cycle
Chlamydiae exist in two distinct morphological forms elementary body (EB) (
infectious form) and reticulate body (RB)(replicating form).

5. Atachment: Elementary bodies attach with specific receptors on the surface of host cells
following which they are endocytosed.
By about eight hours, the elementary body within the endosome undergoes spheroplast-like
transformation to the large reticulate body, which begins to divide by binary fission by 12
hours.
By 20-24 hours, the pleomorphic progeny show central con densation and are converted to
elementary bodies.
The developing chlamydial microcolony within the host cell is called the inclusion body.
The mature inclusion body contains 100-500 elementary bodies which are ultimately released
from the host cell.
Persistent infection: Sometimes, the development is arrested at the reticulate body stage,
leading to persistent ( or latent) infection.

6. CHLAMYDIA TRACHOMATIS
Chlamydia trachomatis is primarily a human pathogen, causing ocular,
urogenital and neonatal infections.
Based on antigenic structure,18 serovars have been identified affecting
humans.
● Serovars A, B, Ba and C are associated primarily with ocular disease called
trachoma.
● Serovars D-K are associated with oculogenital disease, which may be
transmined to neonates.
● Serovars L1-L3 causes a sexually transmined disease, lymphogranuloma
venereum (LGV).

7. Trachoma
Trachoma is a chronic keraroconjunctivitis, caused by C. trachomatis serovars
A, B, Ba and C.
Trachoma is transmitted through direct contact (fingers and formites) with
discharges from the eyes of the infected patients or indirect contact through
contaminated clodies or flies.
Presents as Follicular conjunctivitis. Recurrent infection may lead to
conjunctival scarring and if untreated , blindness.
Trachoma still continues to be a leading cause of preventable infectious
blindness worldwide.

9. lnclusion Conjunctivitis
C. trachomatis serovars D-K cause the following ocular infections.
Ophthalmia neonatorum occurs in new born. The discharge is
mucopurulent compared to gonococcus.
Adult inclusion conjuctivitis: It is an acute follicular conjunctivitis, that may
occur in adults following swimming.

10. Genital chlamydiasis
C.trachomatis serotype D to K are responsible for about 40% of Non-
gonococcal urethritis (NGU).
It is a sexually transmined disease.
It can cause urethritis, epididymitis, proctitis, cervicitis, salpingitis, and pelvic
inflammatory disease.
The symptoms include dysuria, non-purulent discharge, and frequency of
urination.

11. Lymphogranuloma venerum
Lymphogranuloma venereum (LGV) is an invasive systemic sexually
transmited disease.
C. trachomatis serovar L1, L2, and L3 are the agents of LGV
Painless papule, ulcer or vesicle develops on the penis or vulva .
Inguinal lymph nodes in the groin become enlarged, tender and soft (called
bubo), sometimes it may ulcerate.
Systemic symptoms may develop such as fever, headache and myalgia.
in untreated cases, Rectal stricture or recrovaginal and rectal fistulae may
occur.

12. CHLAMYDOPHILA PSITTACI
It causes psitacosis in man and birds.
C. psitlaci can be transmitted to humans by Inhalation of aerosols from avian nasal
discharges and from infectious avian fecal or feather dust.
It can present as mild influenza-like syndrome to a fatal pneumonia.
septicemia occurs which may lead to meningoencephalitis, endocarditis,
pericarditis, arthritis and gastrointestinal symptoms.
Typhoid-like syndrome characterized by fever, heparosplenomegaly and Horder's
spots (rashes resembling the rose spots of typhoid fever).

13. CHLAMYDOPHILA PNEUMONIAE
C. pneumoniae is an exclusively human pathogen. It is transmitted from
person to person by inhalational route. It causes various manifestations:
C. pneumoniae is a common cause of atypical (interstitial) pneumonia.
Upper respiratory tract involvement is frequent such as pharyngitis and
sinusitis.
There is strong evidence of association between C. pneumoniae and
atherosclerosis of coronary and other arteries.
C. pneumoniae may cause exacerbations of bronchial asthma and COPD.

14. LABORATORY DIAGNOSIS
Specimen
● Scrapings or swabs from infected sites.
● Recommended specimens are:
● Urethral swab for NGU
● Endocervical swab for cervicitis
● Conjunctival swabs for ocular infections-upper conjunctiva for trachoma and
lower conjunctiva for ophthalmia neonatorum.
● First catch urine samples in the morning contain greatest amout of urethral
secretions, hence it is the preferred specimen for urethritis or cervicitis.
● Nasopharyngeal aspirate and respiratory secretions for pneumonia.
● Bubo aspirate for LGV.

15. Microscopy
Gram staining: though, chlamydiae are gram-negative they are poorly
stained.
lugol's iodine: the inclusion bodies of C.trachomatis can be stained with
lugol's iodine because of the presence of glycogen matrix.
The Inclusion bodies Halberstaedter-Prowazek (H-P) body is seen in trachoma.

17. Direct Immunofluorescence Test (DIF)
DIF is used as for direct detection of inclusion bodies in clinical material,
particularly from the genital tract and eye.
Though, DIF is sensitive, but the specificily is low because of the non specific
fluorescence.
Enzyme immunoassays
EIA detects chlamydial group specific antigens (LPS) from the samples by using
specific monoclonal antibodies.
Nucleic Add Amplification Tests (NAAT)
NAATs are currently the diagnostic assays of choice for chlamydial infection.
various methods available are: Polymerase chain reaction (PCR), Ligase chain
reaction (LCR) etc

18. Serology (Antibody Detection)
ELISA using recombinant LPS antigen.
Culture
Chlamydiae cannot be cultivated in artificial media.
Cell line culture is considered as the gold standard method.
Cultures are incubated in 10% CO2 for 48-72 hours
Cell lines are then stained to demonstrate the presence of inclusions.

19. Treatment
Chlamydia Trachomatis
uncomplicated genital infection : Azithromycin is the drug of choice.
Alternatively doxycycline, tetracycline, erythromycin or ofloxacin can be given.
complicated genital infection: Doxycycline (100 mg twice daily), or
erythromycin (500 mg four times daily) are the drugs of choice.
For neonatal infections : Erythromycin is given orally. Topical ointments
(erythromycin) can be used in addition to oral therapy for eye infections.

20. Chlamydophila Psittaci
Tetracycline is the drug of choice. Erythromycin (500 mg four times a day by
orally) is given as alternate.
Chlamydophila Pneumoniae
Tetracycline or erythromycin (500 mg four times a day) is recommended for 14
days.

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