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Chlamydia Morphology
Small gram -, atypical outer envelope
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Chlamydia Membrane
- Outer membrane strengthened by disulphide cross-linked cysteine rich membrane protein
- Lacks normal peptidoglycan
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Chlamydia Pathogenicity
- Obligate intracellular parasite
- Cannot be grown on conventional media, only tissue cultures
- Require host-derived ATP
- Non-motile
- No spores
- Strictly pathogenic
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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.
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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
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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)
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Chlamydia psittaci
- Primarily bird/animal pathogen
- Rare in humans (usually human works with animals)
- Causes psittacosis, manifests as acute pneumonia
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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
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Possible association between C. pneumoniae and:
occurrence of coronary atherosclerosis/adult onset asthma
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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
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Lymphogranuloma venereum
- STD from L1-3, Infection of genital tract followed by dissemination to regional lymph nodes.
- Africa and Asia
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Genital Tract Infection
- Transmitted by sexual contact
- trachomatis invades epithelial cells
- Most common bacterial STD
- Often asympotomatic
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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
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Silent PID more common in:
chlamydia
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Chlamydia trachomatis has what type of secretion system
Type III
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Chlamydia need T2SS to do what?
Replicate intracellularly
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Chlamydia genetics
- Intractable system:
- -Intracellular life cycle
- Divergent from other eubacteria
- Most research utilizes genomics, bioinfomatics
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Chlamydia Diagnosis
- Culture (best method)
- Nucleic acid amplification test
- Presumptive (high # PMNs at infection site without Gram - diplococci (gonorrhoeae)
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Rickettsia
Gram - short rods
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Rickettsia Aerobics
Aerobic
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Rickettsia Pathogenicity
- Obligate intracellular parasites
- Can make own ATP
- Arthropod vector
- Cannot be cultured in broth/media
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Rickettsia Cell Structure
- Thin cell wall, more typical gram -
- Have peptidoglycan and LPS
- Stain poorly with Gram stain (use Giesma/Wright)
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Rickettsia rickettsii
- Cause rocky mountain spotted fever
- Found mostly in Southeast
- Transmitted by wood/dog ticks
- Tick is main reservoir
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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
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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
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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
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Endemic/Murine Typhus
- Caused by R. typhi, transmitted by rat/cat fleas
- Rodents are reservoir
- Still similar to RMSF, less deadly
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Who discovered R. rickettsii as cause of RMSF
- Dr. Ricketts
- Died of Rickettsial typhus (anti-irony)
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Rickettsia show:
Actin-Based Motility (ABM)
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