This document summarizes key information about the genus Chlamydia. It describes Chlamydia as small, Gram-negative bacteria that are obligate intracellular parasites. It identifies the main Chlamydia species that can infect humans as C. trachomatis, C. psittaci, and C. pneumoniae. The document outlines how these species can cause ocular, genital, respiratory, and other infections in humans and discusses their laboratory diagnosis and treatment.

1. ‫بسم ا الرحمن الرحيم‬
GENUS: CHLAMYDIA
Prof. Khalifa SifawGhenghesh

2.  Small Gram-negative bacteria (Stain poorly
with Gram’s stain)
 Like Bacteria

Have both DNA and RNA, Ribosomes, a Cell
wall, and Divide by Binary fission
 Like Viruses
 Obligate intracellular parasites
 Differ from Bacteria



Have no peptidoglycan in their cell wall
Can not produce their own ATP
Require to use host ATP (Energy parasite)

3. Chlamydia species
 C. trachomatis

3 biovars
 Those causing trachoma and inclusion
conjunctivitis (TRIC)
 Those causing lymphogranuloma
venereum (LGV)

The one causing mouse pneumonitis (MoPn)
 C. psittaci > Infect both mammals and birds
 C. pneumoniae > both humans and animals
 C. pecorum > Some infect mammals

4.  Trachoma biovars
 14

Serovars: A-K
Serovars A, Ba, B, C
 Classic trachoma

Serovars D-K
 Inclusion conjunctivitis and Genital
infections
 LGV biovars
3
Serovars: L1, L2, L3

5.  Can be stained with Giemsa stain
 Elementary body (EB)
 Extracellular,
infectious metabolically
inert form of chlamydiae
 Reticulate body (RB)
 Intracellular,
non-infectious,
metabolically active particle

7. Infection to Humans
 Ocular infection
 Trachoma > in countries where sanitation
and hygiene standards are poor
 Spread by eye seeking flies, or fingers,
from one patient to another
 Blindness


“Trachoma belt” > North Africa to South-East
Asia
Adult inclusion conjunctivitis
(paratrachoma)


Acute stage >> follicular conjunctivitis
Self-limited

8.  Chlamydial
ophthalmia neonatrum
(inclusion blennorrhoea)
 5-21 days after birth
 If not treated > after 1 year >
secondary bacterial infection >
ocular damage and even blindness
 Source:
 infected genital tract of the mother

9.  Genital infection
 C.
trachomatis is the Commonest
cause of non-gonococcal urethritis
in males (30%)
 LGV
 In both males and females in
tropics and subtropics

10.  In
females
Mucopurulent cervicitis and
urethritis
 Vaginitis and vaginal discharge
 Asymptomatic females if not
treated

 Ascending infection >> Pelvic
inflammatory disease (endometritis
or salpingitis or both)
 Tubal damage >> ectopic pregnancy
and infertility

11.  Infection in pregnancy
 C.
psittaci
Miscarriage or intra-uterine death
 Patients had contact with sheep

 C.

trachomatis
Isolated from abortion products

12.  Respiratory infection
 C. pneumoniae
 3rd or 4th cause of pneumonia
 Pharyngitis, bronchitis, otitis and
sinusitis

C. psittaci
 Psittacosis in humans from avian
strains
 Disease ranges from an influenza-like
illness, to severe illness with typhoidal
state ad pneumonia.

13.  C.
trachomatis
 Pneumonitis in neonates
(infection acquired from the
mother)

14. Laboratory Diagnosis
 Cultivation
 MacCoy cells treated with
cycloheximide
 Organism detected by staining for
inclusions or EBs
 Detects only living cells
 Antigen detection


Using probes for DNA or mRNA that
identify the infected cells
PCR

Amplification of parts of the genome

15. Chlamydia trachomatis
from a urethral scrape

16.  Serology
 Micro-immunofluorescence

Using Ags from all chlamydial
strains to detect species-specific
and serovar-specific Ab
 Complement

test
fixation test
Detecting Ab in serum directed
against group Ag

17. Chlamydia psittaci
Direct FA stained mouse brain impression smear

18. Treatment and Control
 Chemotherapy
 Tetracycline in adults and Erythromycin
in babies


For 3 weeks
Azithromycin

Single dose
 Contact tracing
 Partners of index cases (even if
clinically normal)
 Neonatal infection

Both parents should be treated

19.  Animal contact

Avoidance of contact with sources of
infection (specially pregnant women)


Sheep, milking and shearing
Control of importation of psittacine
birds
 Hygiene