This document summarizes a presentation on Chlamydia given by Sayed Abdullah – Al – Mamun from the Department of Microbiology at Jessore University of Science & Technology. It describes Chlamydia as a genus of bacteria that are intracellular parasites discovered in 1907 by Stanislaus Von Prowazek. It outlines the elementary body and reticulate body morphological forms of Chlamydia and discusses the developmental cycle. It also lists the main species of Chlamydia - C. trachomatis, C. muridarum, and C. suis - and the diseases each causes, including trachoma, urethritis, and pneumonia.
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What is Chlamydia ???
Chlamydia is a genus of bacteria ; that are non
motile , coccid & obligate intracellular parasites .
They contain DNA , RNA & ribosomes . They have
cell wall but peptidoglycan is absent .
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Discovery of Chlamydia
Chlamydia was discovered by Stanislaus Von Prowazek, a
Czech scientist , in 1907 . Before this time , Chlamydia was
recognized as a disease , but the causative agent was not
known . In fact , many thought that gonorrhea was actually
responsible for the symptoms and didn’t realize there were
two different pathogens .
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Chlamydial MorphologiesChlamydial Morphologies
Elementary bodyElementary body
– 0.25 - 0.3 um diameter0.25 - 0.3 um diameter
– electron-dense nucleoidelectron-dense nucleoid
– Released from ruptured infected cells ,Released from ruptured infected cells ,
human to human & bird to human .human to human & bird to human .
Reticulate BodyReticulate Body
– Intracytoplasmic form 0.5 - 1.0 umIntracytoplasmic form 0.5 - 1.0 um
– Replication and growth without a denseReplication and growth without a dense
center.center.
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Evolution ofEvolution of ChlamydiaChlamydia
Gram-negative cocciGram-negative cocci
Facultative intracellular parasites of mammalsFacultative intracellular parasites of mammals
Obligate intracellular parasitesObligate intracellular parasites
Host range restricted to rodentsHost range restricted to rodents
Restricted virulence (compact inclusions)Restricted virulence (compact inclusions)
Folates synthesized (sulfonamide susceptible)Folates synthesized (sulfonamide susceptible)
Glycogen synthesized and deposited in inclusionsGlycogen synthesized and deposited in inclusions
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Diseases by Chlamydia
Chlamydia trachomatis :
It only infects humans .
It causes trachoma ; infection to eyes , which can
lead to blindness .
It also causes urethritis , pelvic inflammatory
disease , ectopic pregnancy , neonatal
pneumonia , and neonatal conjunctivitis .
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Chlamydia muridarum :
It naturally infects only members of the family
Muridae (includes both mice and hamsters) .
Chlamydia suis :
It only infects swine . It causes conjunctivities ,
enteritis and pneumonia in swine
There appears to be no significant difference in morphology or developmental cycle among the various chlamydia, and a single generalized description applies to all. The development cycle may be regarded as an orderly alternation of the small and large cell type. It is initiated by the highly infectious small cell which is taken into the host cell by phagocytosis. The engulfed small cell
retains its morphological integrity in vacuoles bound by membrane derived from the surface of the
host cell, and there is no eclipse (period in which the parasite loses the infectious ability). Instead,
without loss of individuality, the small cell is reorganized into a large cell which is the vegetative
multiplying form of these organisms. Then, still within the membrane-bound vacuole, the large
cell grows in size and multiplies by repeated binary fission. The developmental cycle is completed
by the reorganization of most of the large cells into small ones which are then available for
infection of new host cells. The time required for completion of a cycle varies from 24-48 hours,
depending on the particular host/parasite system involved.