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Chlamydiacae

The taxonomy of Chlamydiacae has been revised on the basis of
genomic studies; and accordingly they have been divided into 2
genera:
Chlamydia
Chlamydia trachomatis
2 biovars
Trachomatis & LGV
Chlamydophila
Chlamydia psittaci
Chlamydia pneumoniae

They were once considered as viruses because :
They are small enough to pass through o.45µ filters
They are obligate intracellular parasites.

They are now considered as bacteria because:
1.They have inner & outer membranes similar to gram negative
bacteria.
2. They contain both DNA &RNA
3.They can synthesize their own proteins, nucleic acids & lipids
4.They are susceptible to many antibiotics.
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Antigenic structure
1. They have a genus-specific lipopolysaccharide detected by
complement fixation test.
2. They have species &strains-specific outer membrane proteins
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Staining
1. Giemsa………….stains the elementary bodies , the reticulate
bodies &inclusions (not for definitive diagnosis )
2. Gram……………gram negative or gram variable (difficult )
3. Immunofluorescense
4. Iodine……………for intracellular inclusions which contain
glycogen
Developmental cycle of Chlamydia

-EB (elementary body ) attaches to the
surface of susceptible cell & enters the
cell by phagocytosis
-The elementary body organizes into
RB ( Reticulate body ).
-The reticulate body divides by binary
fission.
-After 24-48 hrs ,EBs are released and
initiate a new cycle of infection
-The mass of EBs → Inclusion
body→detected by histologic stains
NB 1-After internalization,bacteria remain
within the cytoplamic phagosome &
replicate.
2-Fusion of cellular lysosomes &
EBs containing phagosome , and
subsequent intracellular killing is
inhibited (bacteria not affected by
lysosymes
Growth
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Eukaryotic cell lines : Hela cells-229 , Mc Coy cells , BHK -21 , Buffalo green
monkey kidney cells.
Sensitivity is increased by pretreatment with cycloheximide (to decrease host
metabolism ), use of shell vial technique ( growth of host cell monolayer on
glass cover slips rather than in small microtiter plates), use of Iodine stain or
Fluorescein-conjugated antibodies to detect intracellular inclusions.
- Embryonated egg yolk sac.
- Mice (rarely used )
Reaction to physical & chemical agents
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Heat …………….at 60°C,for 10 min leads to their inactivation
Ether……………..for 30 min………..leads to rapid inactivation
Phenol 0.5%, for 24h…………………leads to inactivation
Freeze drying…………………………decreases their infectivity
Dryness……………………………….does not affect infectivity
Treatment
- Both sex-parteners should be simultaneously treated
- Tetracyclins are commonly used in non-gonococcal urethritis and in
non-pregnant females.
- Azithromycin is also effective.
- Erythromycin may be an alternative in pregnant females
- Topical Tetracyclin or Erythromycin………for inclusion
conjunctivitis.
- In LGV……….Sulfonamides & Tetracyclins for the early stages;but
late stages require surgery.
Chlamydia Trachomatis

It has a very limited range of infection (infects humans only)

It has 2 Biovars:
Trachoma (15 serovars A,B,Ba,C,D-K )
LGV
(4 serovars L1,L2,L2a,L3)
Clinical syndromes
1. Infections in Adults

Non-gonococcal urethritis (NGU) in males
- 50% of cases of NGU are sexually acquired.
- 25% are asymptomatic but are able to transmit the organism.
- When symptoms occur (urethral discharge,difficult micturition),they are
mild (unlike gonococcal urethritis).Serious complications are rare.

Mucopurulent cervicitis in females
- It is the female counterpart of male NGU
- It is acquired through sexual intercourse.Many remain asymptomatic.
- The Gram stain of the endocervical swab shows yellow-green mucous and
more than 10 PNLs/ HPF.(Neisseria must be excluded)
- Complications include PID

Pelvic inflammatory disease (PID)
- It is an ascending infection.
- Although symptoms may be mild yet laparoscopy may show severe
inflammation.
- Complications include salpingitis, endometritis,peritonitis,
Prihepatitis(Fitz-Hugh Curtis syndrome).These may lead to
infertility,chronic pelviabdominal pain & ectopic pregnancy.

Lymphogranuloma venereum
- It is a sexually transmitted disease.
- The IP is about 4w.
- The primary lesion occurs at the site of infection:vesicle,papule or
ulcer,small,painless heals rapidly so it might be overlooked.
- The second stage which occurs after2-5w shows marked inflammation&
swelling of the lymph nodes (usually inguinal)
- There is constitutional symptoms (usually severe).Fistulae may form
(especially after needle aspiration)
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Acute urethral syndrome
Occurs in young women in the form of recurrent dysuria,pyuria& sterile
culture
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Ocular infections
1- Trachoma :( A,B,Ba,C ) keratoconjunctivitis,invasion of blood vessels into
the cornea,bacterial infection&scarring.
2- Inclusion conjunctivitis :( A,B,Ba,D-K) in sexually active adults. It may
occur as an autoinfection.
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Proctocolitis &epididymitis
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Reiter' s syndrome: conjunctivitis,reactive arthritis and urethritis.
2. Infections in infants
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Newborns………..from infected birth canal
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Infants pneumonia (1-6 mo ) : usually associated with
conjunctivitis.
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Infants conjunctivitis :It is the commonest cause of neonatal
conjunctivitis& is associated with mucopurulent discharge(2-3w
after birth).Most cases resolve without sequelae. However,some
may develop chronic ocular infection
Diagnosis
1. Culture
2. Non-cultural methods:
- Cytology : cell scrapings for inclusions,but is insensitive compared to culture
&immunofluorescence.
- Antigen detection: by direct immunofluorescence,
than culture)
ELISA(less sensitive
- Nucleic acid probes: test the presence of a specific species-specific sequence
of 16S rRNA.It is rapid & relatively inexpensive.
- PCR,LCR,TMA (transcription mediated amplification), SDA (standard
displacement ).They have a sensitivity of
90-98% In the very near future,they will be the test of choice.
- Serology: has a limited value in Chlamydia trachomatis causing genital
infections in adults,because antibody titers persist for a long period so,do not
differentiate between concurrent and past infections; although a significant rise
in antibody titer is useful.
Chlamydia Psittaci

Causes Psittachosis, Ornithosis, Parrot fever

Humans are infected by contact with birds, inhalation of dried
bird excrement, urine or resp. secretions.
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IP 4d
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C/ P: From mild inapparent or flu like inf. to severe pneumonia
with sepsis and high mortality rate (20%) now decreased to 2%.

Path: RT
lungs.
Blood
Liver, Spleen, Kidneys and
Diagnosis
1) Serology: 4 fold rise by CFT  confirm by MIF
Sometimes specific IgM Antibody can be demonstrated.
2) Cell culture: rarely performed
Treatment
Te, Macrolides
Chlamydia Pneumoniae

Was 1st isolated from conj. of a child in Taiwan (TW-183) and
was found to be related to a pharyngeal isolate (AR-39) 
TWAR  C. pneumoniae 
Chlamyolophila ( only a
single serotype)
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Transmitted by resp. secretions (person to person)
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Human pathogen
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Common in adults
Clinical Picture
Usually mild or asymptomatic
 May cause bronchitis, pneumonia, sinusitis
 Cannot be diff. from other atypical pneumonias (Mycopl,
Legionella,….)
 Associated with atherosclerosis
Diagnosis 
difficult
 Do not grow
 Amplification techniques √
 Serology:
 Complement Fixation: not specific (positive for both
Chlamydia and Chlamydophia)
 IF √√ : the most sensitive and specific. It uses EBs as
antigens
Treatment
 E, Te, Lev
10-14d

Characteristics of the Chlamydiae
C. Trach.
C. Pneum.
C. Psittaci
Inclusion
Morphology
Round, Vaeuolar
Round, Dense
Large, Variable
Shape, Dense
Glycogen in Inclu.
Yes
No
No
E B Morph.
Round
Pear Shaped
Round
Suspect. To Sulph.
Yes
No
No
Serovars
19
Natural Host
Humans
Mode of
Transmission
 Person to person
 Mother to infant
 Trachoma
 STDs
 Infant pneumonia
 LGV
Major Disease
1
Humans
Air borne
Person to person
Pneumonia
Bronchitis
Pharyngitis
Sinusitis
≥4
Birds
Air borne (bird
excreta to human )
Psittacosis
Pneumonia
Fever of U.O