24/02/2008dr ekta, microbiology, gmca chlamydia ii mbbs

24/02/2008 Dr Ekta, Microbiology, GMCA

CHLAMYDIA

II MBBS


KEY WORDS

IntracellularEnergy parasitesElementary bodyReticulate bodyInclusion bodies – HP, LCLBiotypes/ serotypesTissue cultureC. trachomatis

Trachoma

Inclusion conjunctivitisLymphogranuloma venereumFrei testGenital chlamydiasisC. psittaci

PsittacosisOrnithosisC. pneumoniae


INTRODUCTIONObligate intracellular parasites of humans, animals & birds

Resemble bacteria except it cannot multiply outside living cells/ tissues (like viruses)

Cannot synthesize ATP – depends on host cell for energy & nutrient sources. Hence, called Energy Parasites.


CHLAMYDIA

4 species in the Genus Chlamydia – C. trachomatis, C. pneumoniae, affects humans C. psittaci and C. pecorum affects ruminants

All are non-motile, gram negative; share antigens, have both DNA and RNA.


ClassificationC.trachomatis : eye & genital infections, infant pneumonia, and LGV (Lymphogranuloma Venereum) in adults

C.pneumoniae : different types of respiratory infections.

C.psittaci : psittacosis in man, ornithosis in birds


Life cycle Chlamydiae occur in 2 forms :

1. Elementary body – extracellular, infective form2. Reticulate body – intracellular, growing & replicative

form

• Chlamydial microcolony within the host cell is called Inclusion body.

• Mature inclusion body contains 100 - 500 elementary bodies


Life cycle

C. psittaci – host cell is severely damaged, EBs are released within 48 hrs by cell lysis

C.trachomatis – mature inclusion body appears to be exocytosed in 72- 96 hrs.


Antigenic Properties

Three major Ags1. Genus specific Ag – heat stable, common to all chlamydiae,

a lipopolysaccharide resembling LPS of GNB. Present in all stages.

2. Species specific protein Ags – present at the envelope surface, help in classifying chlamydia into species

3. Ag for Intraspecies typing – found only in some members of a species, located on major OMP (MOMP), demonstrated by micro- IF. Classifies species into serovars/ serotypes


Variants of Chlamydia

C. trachomatis – 2 biovars: TRIC & LGV1. TRIC – Trachoma, Inclusion conjunctivitis - divided into 12 serovars

2. LGV – Lymphogranuloma venereum – 3 serovars


Human diseasesSpecies Serotype Disease

C. trachomatis A, B, Ba, C Endemic blinding trachoma

C. trachomatis D to K Inclusion conjunctivitis. Genital chlamydiasis

C. trachomatis L1, L2, L3 Lymphogranuloma venereum

C. psittaci Many serotypes Psittacosis

C. pneumoniae Acute resp. disease


Laboratory Diagnosis

4 approaches available:1. Microscopic demonstration of inclusion or

elementary bodies2. Isolation of chlamydia3. Demonstration of chlamydial Ag4. Demonstration of Abs or hypersensitivity


Microscopy Gram negative but stained better by Giemsa, Castaneda or Machiavello stains.Giemsa Stain: Elementary body & the Reticulate body stains blue in cytoplasmLugol’s iodine: rapid & simple screening method for ocular infections, stains glycogen matrix of C. trachomatis

Immunoflurescence staining: more sensitive & specific, by using monoclonal Abs. Identifies inclusion bodies as well as extracellular elementary bodies. Used for ocular, cervical or urethral specimens.


IF staining


Culture

Yolk sac of 6 - 8 days old chick embryo.

Tissue culture – McCoy, HeLa cell lines

* C. psittaci carry the risk of laboratory infection.


Microscopic appearance

A monolayer of tissue culture cells has been exposed to cells of chlamydia trachomatis. Infected cells within the cell sheet have a cytoplasm with a granular appearance.


Demonstration of antigens

Micro – IF : infected ocular or genital samples are stained with fluorescent conjugated Ab

ELISA – best for screening large number of specimens, detects LPS Ag

Molecular methods - PCR


Chlamydia trachomatis

Leading cause of ocular & genital infectionsPathogenicities:

1. Trachoma2. Inclusion conjunctivitis3. Infant pneumonia4. Genital infections – genital chlamydiasis, LGV


Trachoma

Greek word trakkus – rough (roughness of conjunctiva)Caused by C. trachomatis types A, B & C.Chronic keratoconjunctivitisTransmitted by fingers, fomites, flies or dustEstablished trachoma passes through 4 stages (I – IV).Infectivity is maximum in early cases, stage IV is non infectious.


Laboratory diagnosis of Trachoma

Demonstration of characteristic inclusion bodies (Halberstaedter Prowazek or HP bodies) in conjunctival scrapings by Giemsa.

Culture – yolk sac, cell lines


Treatment & Control

Local application of antibioticsOral administration - Tetracycline or Doxycycline for several weeksSingle dose Azithromycin

Control – mass education & chemotherapy


Inclusion ConjunctivitisCaused by C. trachomatis types D to K

Naturally present in the genital tract

Neonatal form - “Inclusion Blenorrhoea”, develops when the infant is in birth canal, appears 5-12 days after birth, prevented by local application of antibiotics

Adult form – “Swimming Pool Conjunctivitis” – associated with bathing in community swimming pools contaminated with chlamydia from genital secretions.


Infant Pneumonia

Usually occurs around 4-16 wks of age.Cough & wheezing. Rarely feverConjunctivitis often precedes pneumonia


Genital Infections

Two types :1. Genital chlamydiasis2. Lymphogranuloma venereum


Genital chlamydiasisMost common STD, clinical spectrum similar to gonococcal infections.Men – urethritis (NGU), epididymitis, proctitis & Reiter’s syndromeWomen – acute urethral syndrome, mucopurulent cervicitis, endometritis, salpingitis, PID, infertility, ectopic pregnancy, premature delivery, postpartum fever.

Diagnosis – gram stained smears of urogenital exudates showing – more than 4 neutrophils / OIF in urethritis, – >30 / OIF in cervicitis.

Confirmatory tests – culture, micro-IF, ELISA, PCR


Lymphogranuloma venereum

Most commonly caused by L2 typeSite – regional lymph nodesIncubation period – 3 days to 5 wks1° lesion – small painless papulovesicular lesion on external genitalia2° stage – after 2 wks, lymphatic spread to draining LNs (men – inguinal, women – intrapelvic & pararectal)


Lymphogranuloma venereumNodes enlarge, suppurate, become adherent to the skin & break down to form discharging sinuses.

Metastatic complications – may occur, involves joints, eyes & meninges3° stage – chronic, lasts for several years; scarring & lymphatic blockageLate sequelae more distressing in women – rectal strictures, elephantiasis of vulva (esthiomene)


Laboratory Diagnosis of LGV

Demonstration of elementary bodies in materials aspirated from bubos (inguinal)Isolation – cell culturesSerology – detection of Abs

1. CFT 1: 64 or more2. Micro- IF 1: 512 or more

Frei Test – ID test using crude chlamydial Ag, not done now.


Chlamydia psittaci

Causes Psittacosis – disease of parrotsShed in the droppings or nasal discharges and aerosols are liberated.Humans – occupational disease as in poultry workers, pigeon farmers, petshop owners, veterinarians; laboratory acquired infection

Infection by inhalation.

Mild influenza like syndrome to fatal pneumonia


Laboratory Diagnosis

Specimen – blood (early stages), later sputumDemonstration of LCL (Levinthal-Cole-Lillie) Inclusion bodies in alveolar macrophages, mouse brain, yolk sac, cell cultures LCL bodies - more diffuse & irrregular, not stained by iodineSerology – CFT, micro-IF


Chlamydia pneumoniaeIsolated in 1986 from acute respiratory diseases in adults in Taiwan – C. psittaci strain TWARLater classified as a separate species.Common cause of respiratory disease in older children & adults.C/F – pharyngitis, sinusitis, bronchitis & pneumonia (atypical pneumonia)Outbreaks in closed communities.Reinfections are common.


Chlamydia pneumoniaeDiagnosis – Ag detection by EIA, direct IF, PCR, as isolation is very difficult.Treatment – clarithromycin or azithromycinNewer findings – suspected to be associated with atherosclerosis and its clinical effects like coronary, carotid & cerebral arterial disease.Evidences – detection of chlamydial Ags in plaques, isolation of chlamydia from coronary artery plaques, experimental induction of atheroma in rabbits infected with chlamydia


So…What’s Chlamydia anyways?

How is it detected, treated and prevented?

If it happens to me, what do I do?

What are the possible complications?

Chlamidia

24/02/2008dr ekta, microbiology, gmca chlamydia ii mbbs

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