Review%20from%20last%20time:%20Mycobacterium%20tuberculosis - PowerPoint PPT Presentation

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Review%20from%20last%20time:%20Mycobacterium%20tuberculosis

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Review from last time: Mycobacterium tuberculosis – PowerPoint PPT presentation

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Title: Review%20from%20last%20time:%20Mycobacterium%20tuberculosis


1
Review from last timeMycobacterium tuberculosis
  • Microbiology of M. tuberculosis
  • History and Epidemiology
  • Immunobiology and Disease
  • Testing and Vaccination
  • Therapy chemoprophylaxis and treatment
  • Drug Resistance
  • Host susceptibility

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Some after-thoughts on TB
  • Why treat latent TB?
  • Why do the skin test or vaccine NOT cause
    disease?

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Skin Wound infections
  • Denise Kirschner, Ph.D.
  • Dept. of Micro/Immuno
  • MICRO 532 Nov 28, 2001
  • Chapters

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Outline
  • Skin Infections
  • Contrasting Staph aureus with Strep pyogenes
  • Folliculitis, boils and carbuncles
  • Rocky mountain spotted fever (R. rickettsii)
  • Lyme disease (B. burgdorferi)
  • Anthrax (Bacillus anthracis)
  • Bacterial infections of Wounds
  • Tetanus (C. tetani)
  • Gangrene (C. perfringens)
  • Burn infections (P. auerginosa)
  • Actinomycosis (A. israelii)

5
SKIN- anatomy and physiology
  • Large complex organ covering the external body
    surface
  • Protective layer offers resistance to infection-
    acidic, dry, unstable, toxic
  • Important role in vitamin D synthesis
    (bones/teeth)

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Produce sebum
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Hair follicle
Skin surface
Propionibacteria
INDIGENOUS MICROFLORA 3 groups 1)Propionibacteriu
m acnes (Corynebacterium genera)- G,
non-motile 2)Staphylococci (S. epidermis is the
primary) Colonization resistance 3)Malassezia
(yeast)
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Outline
  • Skin Infections
  • Contrasting Staph aureus with Strep pyogenes
  • Folliculitis, boils and carbuncles
  • Rocky mountain spotted fever (R. rickettsii)
  • Lyme disease (B. burgdorferi)
  • Anthrax (Bacillus anthracis)

10
Folliculitis, boils and carbuncles- most caused
by S. aureus
  • Infection of the hair follicle
  • Folliculitis red bump, remove hair and resolves
  • Boil- if infection extends into local tissues
    causing inflammation (rubor, dolor, tumor, color)
  • pus drainage
  • Carbuncles-large area of inflammation with
    several sites of draining pus- usually develop in
    areas of skin that are thick (accompanied by
    fever plus other signs of serious infection)
  • Other skin infections caused by b-hemolytic,
    group A Streptococci- Flesh eating bacteria and
    most skin infections as well

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S. aureus infects a hair follicle (a)
(b)infection spreads Deeper into the tissue Where
abscess develops
c) An abscess forms below the skin with necrotic
plug
AbscessLocalized collection of pus
12
Staphylococcus aureus
  • Facultative anaerobe, G coccus
  • Virulence Factors
  • Capsule (inhibit phagocytosis)
  • Protein A (binds Fc portion of Ab, inhibiting
    phagocytosis)
  • TSST (toxin that causes rash, diarrhea, shock)
  • Coagulase (impedes leukocyte recruitment)
  • Epidermolytic toxin (separates layers of skin
    causing scalded skin syndrome) newborns, elderly
    etc
  • Can be part of IM in almost all persons (nose)

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S. aureus
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Pyoderma
  • Skin infection characterized by pus production
  • Results from infection of an insect bite, burn or
    other wound
  • Impetigo- the most common type
  • Superficial skin infection
  • Isolated pustules that weep become crusted and
    rupture
  • Caused by both S. pyogenes gtgt S. aureus
  • Reminder S. pyogenes (b-hemolytic group A)
  • Treatment penicillin or other anti-staph
    antibiotic

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Streptococcus pyogenes
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Impetigo. This type of pyoderma is often caused
by Streptococcus pyogenes and may result in
glomerulonephritis.
17
Outline
  • Skin Infections
  • Contrasting Staph aureus with Strep pyogenes
  • Folliculitis, boils and carbuncles
  • Rocky mountain spotted fever (R. rickettsii)
  • Lyme disease (B. burgdorferi)
  • Anthrax (Bacillus anthracis)

18
Rocky Mountain Spotted Fever
  • Caustive agent Rickettsia rickettsii
  • Obligate, intracellular, G-, non-motile
  • Induces endocytosis by host cells (small blood
    vessel-lining cells)
  • Very hard to diagnose
  • Zoonotic transmission- mammalian tick is carrier
    (Dermacentor species) dog/tick
  • Requires 4-10 hour feed to transmit
  • Symptoms headaches, sore joints, rash
  • Treatment with antibiotics works if given early
    enough. W/o treatment- 20 death rate, (higher in
    elderly)

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1990
Rocky Mountain spotted fever
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Lyme Disease
  • Isolated in 1982 in Lyme, Connecticut
  • Causative agent Borrelia Burgdorferi a
    spirochete (not G/G-)
  • Deer/mouse/tick zoonosis
  • Disease stages and some mimic others (i.e.
    flu-like)
  • Stage 1 (incubation) hallmark bullseye rash
    erythema chronicum migrans (after stage 1,
    difficult to isolate bacteria)
  • Stage 2 2-8 weeks -heart and CNS impairments
    leading to paralysis and fatigue
  • Stage 3 6 months after rash- arthritis and joint
    swelling (can last for years)
  • Most common vector borne disease in USA
  • Treatment preventionprotection, antibiotics if
    early

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Outline
  • Skin Infections
  • Contrasting Staph aureus with Strep pyogenes
  • Folliculitis, boils and carbuncles
  • Rocky mountain spotted fever (R. rickettsii)
  • Lyme disease (B. burgdorferi)
  • Anthrax (Bacillus anthracis)

30
Bacillus anthracis
  • G, soil organism that mainly infects cattle,
    sheep, goats and horses
  • No human-human transmission
  • Has a spore form (very stable!)
  • Cutaneous anthrax If spore enters skin abraision
    a pimple develops that later becomes a blister
    with a swollen black scab. Usually curable.
  • Spores can enter through inhalation (or
    ingestion)- almost 100 fatal in a few days (high
    bacteremia)
  • Virulence capsule and toxin
  • Since 1970 groups of military immunized
  • No real incidence /prevalence in human pops

31
Pathogenesis
  • Endospores introduced into the body are
    phagocytized by macrophages and then germinate to
    vegetative bacteria.
  • Intracellular stages take several hours.
  • Mf take up all spores types rapid efficient.
  • Anthrax spores have Mf-specific germination
    systems signals.
  • Newly germinated bacilli escape the phagolysosome
    can grow in cytoplasm (membrane active toxins).
  • Vegetative bacilli are released from host Mf into
    the blood. (108 /ml of blood)

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TOXINS- A-B type
  • Lethal toxin lethal factor (LF) protective
    antigen (PA)
  • Stimulates Mf to release TNF-a and IL-1- both
    leads to shock and sudden death in systemic
  • Edema toxin edema factor (EF) PA
  • Edema in cutaneous anthrax due to cyclic AMP
    homeostasis upset
  • PA is the binding moeity (like the B in A-B)

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1-2 mm
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Outline
  • Bacterial infections of Wounds
  • Tetanus (C. tetani)
  • Gangrene (C. perfringens)
  • Burn infections (P. auerginosa)
  • Actinomycosis (A. israelii)

40
Tetanus
  • Clostridium tetani
  • Anerobic, motile G rod, spore forming
  • Pathogenesis release of exotoxin that is
    extremely potent when taken up by nerve cells
    lockjaw
  • Ubiquitous in soil /dust
  • Prevention and treatment antitoxin together with
    TIG (tetanus immunoglobulin). Immunization with
    DPT. Toxoid. NEED boosters.

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C. tetani- tennis racket appearance
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Tetanus Incidence
45
Gas Gangrene
  • Caused by Clostridium perfringens
  • Grows easily in dead or poorly oxygenated tissues
  • Releases toxin
  • A complication of dirty or neglected wounds

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Burn infections
  • Pseudomonas aeruginosa
  • Ubiquitous organism found in soil, water, etc
  • Prevents healing
  • Produces tissue damage
  • Promotes septic shock
  • Toxin similar to diptheria toxin
  • Treatment- highly resistant, but some antibiotics
    work at high doses

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Actinomycosis can develop following dental surgery
  • A slow progressive infection characterized by
    painful swelling under the skin that eventually
    opens and drains pus chronically (head/neck)
  • Actinomyces israelii G, anaerobic bacterium
    (mistakenly named as a fungus)
  • lumpy jaw
  • Infection has cycles of abscess formation,
    scarring and pus tracts.
  • Introduced (from IM) into wounds along with other
    bacteria (dental procedures)
  • Seems to heal only to return days or weeks later

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