MMI 301: Lecture 25: Chlamydia/Rickettsia

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  1. Chlamydia Morphology
    Small gram -, atypical outer envelope
  2. Chlamydia Membrane
    • Outer membrane strengthened by disulphide cross-linked cysteine rich membrane protein 
    • Lacks normal peptidoglycan
  3. Chlamydia Pathogenicity
    • Obligate intracellular parasite
    • Cannot be grown on conventional media, only tissue cultures
    • Require host-derived ATP
    • Non-motile
    • No spores
    • Strictly pathogenic
  4. Chlamydia cell envelope structure
    • LPS: present but not very inflammatory
    • MOMP: Major outer membrane protein (used to serotype chlamydia)
    • Abundant cysteine rich proteins disulfide bonded may make up for lack of peptidoglycan in cell envelop.
  5. Chlamydia lifecycle
    • Attachment of Elementary Bodies to cell and ingestion (T3SS secretes Ct694/Tarp
    • EB fuses with phagosome
    • EB reorganized into Recirculate Body
    • RB multiply, migrate to perinuclear region, nutrient acquisition. 
    • Condensation of RB to EB, Inclusion expands
    • Becomes mature inclusion
    • Extrusion and release of EB after cell death from immune
  6. Species of Chlamydia
    • C. psittaci
    •      -Many serotypes
    •      -Psittacosis
    • C. pneumoniae
    •      -One serotype
    •      -Acute respiratory infection
    • C. trachomatis
    •      -15 serotypes
    •           -A, B, Ba, C: Trachoma
    •           -B, D, E, F, H, I, J, K: Lots
    •           -L1-3: Lymphogranuloma venereum
    •            (LGV)
  7. Chlamydia psittaci
    • Primarily bird/animal pathogen
    • Rare in humans (usually human works with animals)
    • Causes psittacosis, manifests as acute pneumonia
  8. Chlamydia pneumoniae
    • New pathogen
    • Cause respiratory disease
    • Incidence and prevalence determined by serotyping
    • 50% adults have serum antibodies, probably has infect near everyone at some point
  9. Possible association between C. pneumoniae and:
    occurrence of coronary atherosclerosis/adult onset asthma
  10. Trachoma
    • Caused by serovars A, B, Ba, C (trachomatis)
    • Found in areas of poor hygiene
    • Cause of infectious blindness
    • Disease from repeated inflammatory infection of conjuntiva
    • Blindness from repeated scratches of cornea from disfigured eyelids
    • Asia and Africa
  11. Lymphogranuloma venereum
    • STD from L1-3, Infection of genital tract followed by dissemination to regional lymph nodes.
    • Africa and Asia
  12. Genital Tract Infection
    • Transmitted by sexual contact
    • trachomatis invades epithelial cells
    • Most common bacterial STD
    • Often asympotomatic
  13. Urogenital disease (trachomatis)
    • Less purulent than N. gonorrhoeae
    • Mild purulent inflammation, results from infection/destruction of epithelial cells of genital areas
    • Long term disease is immune-mediated
    • Inflammation=PID, tubal scars, ectopic pregnancy, infertility
  14. Silent PID more common in:
  15. Chlamydia trachomatis has what type of secretion system
    Type III
  16. Chlamydia need T2SS to do what?
    Replicate intracellularly
  17. Chlamydia genetics
    • Intractable system:
    • -Intracellular life cycle
    • Divergent from other eubacteria
    • Most research utilizes genomics, bioinfomatics
  18. Chlamydia Diagnosis
    • Culture (best method)
    • Nucleic acid amplification test
    • Presumptive (high # PMNs at infection site without Gram - diplococci (gonorrhoeae)
  19. Rickettsia
    Gram - short rods
  20. Rickettsia Aerobics
  21. Rickettsia Pathogenicity
    • Obligate intracellular parasites
    • Can make own ATP
    • Arthropod vector
    • Cannot be cultured in broth/media
  22. Rickettsia Cell Structure
    • Thin cell wall, more typical gram -
    • Have peptidoglycan and LPS
    • Stain poorly with Gram stain (use Giesma/Wright)
  23. Rickettsia rickettsii
    • Cause rocky mountain spotted fever
    • Found mostly in Southeast
    • Transmitted by wood/dog ticks
    • Tick is main reservoir
  24. Rock Mountain Spotted Fever
    • Fever, headache, chills, muscle pain, nausea
    • Rash after 2-5 days
    • Characteristic red spotted rash
    • Can lead to multiple organ failure
    • Long term sequelae of acute disease includes partial paralysis of lower extremities, gangrene-->amputation, movement/language disorders
  25. Rickettsia Diagnosis
    • Can be grown in culture
    • Staining is hard, usually used in autopsy, not diagnosis
    • Diagnosis based on presentation and detection of anti-rickettsial antibodies
    •      -Indirect fluorescence assay
    •            -Detects IgM or IgG
  26. Epidemic/Louse-borne Typhus
    • Caused by Rickettsia prowazekii
    • Transmitted by louse
    • Humans are primary reservoir
    • Cramped/Poor hygiene promote
    • Historically effects armies
    • Looks like RMSF, more deadly
  27. Endemic/Murine Typhus
    • Caused by R. typhi, transmitted by rat/cat fleas
    • Rodents are reservoir
    • Still similar to RMSF, less deadly
  28. Who discovered R. rickettsii as cause of RMSF
    • Dr. Ricketts
    • Died of Rickettsial typhus (anti-irony)
  29. Rickettsia show:
    Actin-Based Motility (ABM)
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MMI 301: Lecture 25: Chlamydia/Rickettsia
MMI 301
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