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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)
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
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
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
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
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
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
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
Infection in pregnancy C. psittaci
Miscarriage or intra-uterine death Patients had contact with sheep
C. trachomatis Isolated from abortion products
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.
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
Serology Micro-immunofluorescence test
Using Ags from all chlamydial strains to detect species-specific and serovar-specific Ab
Complement fixation test Detecting Ab in serum directed against group Ag
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