Chlamydia

Dr. Hala Al-Daghistani

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• Chlamydia is a genus of pathogenic bacteria that are obligate intracellular

parasites of mammals and birds.

• Classification – order chlamydiales – contains one medically important genus

– chlamydia

• Chlamydia infections are the most common bacterial Sexually transmitted

diseases in humans and are the leading cause of Infectious blindness

worldwide.

• Reported rates 3 times higher in females than in males.

• contain DNA and RNA, and ribosomes, lack ATP, biosynthetic pathways, non motile. Multiply in the cytoplasm of the host cell. Three important spp.,

C. trachomatis

C. psittaci

C. pneumoniae

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Transmission

• Transmission is sexual, RT, or vertical

• Highly transmissible

• Incubation period 7-21 days

• Significant asymptomatic reservoir exists in the

population

• Re-infection is common

• Perinatal transmission (relating to the time, immediately

before and after birth) results in neonatal conjunctivitis

in 30%-50% of exposed babies

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Have a complex developmental cycle

The infectious form is called an Elementary Body (EB) which is circular in form and is taken into the cell by induced phagocytosis.

Inside the phagocytic vesicle replication takes place. Over the next

6-8 hours, the EB reorganizes into the noninfectious, but metabolically active Reticulate Body (RB) which is larger and less

dense than the EB.

For 18-24 hours the RB synthesized new materials and divides by binary division to form Inclusion Bodies that reorganize and

condense into EBs. Between 48-72 hours, the cell lyses and releases the EB which begin

the cycle again.

• Elementary body

– 0.25 - 0.3 um diameter

– electron-dense nucleoid

– Released from ruptured infected cells. Human to human

– & bird to human.

• Reticulate Body

– Intracytoplasmic form 0.5 - 1.0 um

– Replication and growth. ( Inclusion body )

– without a dense center.

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http://journal.frontiersin.org/article/10.3389/fimmu.2014.00534/full

Chlamydia inclusion bodies

Chlamydiaceae Family

Species (genus) Disease

C. Trachomatis

(many serotypes)

Trachoma, NGU, PID, neonatal

conjunctivitis, inclusion conjunctivitis,

Infant pneumonia, LGV

C. Pneumoniae

(TWAR) Taiwan acute respiratory agent

Pharyngitis, Bronchitis, Pneumonia

C. psittaci

(many serotypes) Psittacosis(influenza-like illness)

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Clinical significance 1. Chlamydia trachomatis - Genital tract infection– is sexually transmitted and frequently found

concomitantly with N. gonorrhoeae (In males symptoms include urethritis, dysuria and it sometimes progresses to epididymitis; In females symptoms include mucopurulent cervical inflammation which can progress to salpingitis and PID).

- Inclusion conjunctivitis –occurs in both newborns and adults and a genital tract infection is the source of the infection.

- Newborns are infected during the birth process, with a mucopurulent discharge.

- In adults causes an acute follicular conjunctivitis with little discharge (autoinoculation).

- Trachoma, greatest cause of blindness in underdeveloped countries.

(Transmission is by direct contact, flies, and in poor, less developed countries, children may be infected in the first three months of life.

- Lymphogranuloma venereum (LGV) is a venereal disease that occurs in

poor, tropical areas. painless lesion occurs at the site of entry with symptoms of regional suppurative lymphadenopathy (buboes)

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Inclusion conjunctivitis - foreign body sensation

- watery eyes - eyelids that stick together

-Large follicles may be seen if the

lower lid is pulled down.

Trachoma The inside of the eyelid can become so

severely scarred that causes the eyelashes to rub against the eyeball,

impairment breakdown and scarring of the cornea, resulting in constant pain

and light intolerance

Left untreated, leads to visual and eventual blindness

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Chlamydia psittaci naturally infects avian species causing

mild to severe illness (affect bird beak, eyes, RT, GIT, feathers) .

In man causes psittacosis ) parrots fever, ornithosis) and is acquired by contact with an infected animal.

Infection can range from subclinical to fatal pneumonia.

Most commonly causes an Atypical pneumonia with fever, chills, dry cough, headache, sore throat, nausea, and vomiting.

Chlamydia pneumoniae

This bacterium was recognized as a Resp.

pathogen, after isolation from pharyngitis

Pneumonia or Bronchitis, gradual onset of

cough with little or no fever. Less common

presentations are Pharyngitis, Laryngitis,

and Sinusitis

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Pathogenesis - Chlamydiae have a hemagglutinin that may facilitate attachment to cells. - An endotoxin-like toxin has been described.

Laboratory Diagnosis

• Culture

• Non-culture tests

– Nucleic Acid Amplification Tests

– Non-Nucleic Acid Amplification Tests including Direct fluorescent antibody (DFA)

– Nucleic acid hybridization (NA probe)

– Serology (EIA) Enzyme immunoassay.

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Prevention

• Nature of the infection – Chlamydia is commonly asymptomatic in men and women.

– In women, there is an increased risk of upper reproductive tract damage with re-infection.

• Transmission issues – Abstain from sexual intercourse until partners are treated

for 7 days after a single dose of azithromycin

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