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Pseudomonas Gram negative bacteria Rod-shaped, polar flagella (hence, motile) Inhabit the soil and water Pseudomonas aeruginosa is the most prevalent opportunistic ... – PowerPoint PPT presentation

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Title: Pseudomonas

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  • Gram negative bacteria
  • Rod-shaped, polar flagella (hence, motile)
  • Inhabit the soil and water
  • Pseudomonas aeruginosa is the most prevalent
    opportunistic pathogen
  • Intrinsically resistant to many antibiotics ?
    nosocomial infection
  • combinations gt2 drugs (eg. Penicillin

P. aeruginosa
  • Obligate aerobe
  • Produce a sweet or grape-like smell
  • Colonies with a fluorescent greenish colour,
  • nonfluorescent bluish pigment pyocyanin
  • greenish pigment pyoverdin
  • dark red pigment pyorubin
  • black pigment pyomelanin

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  • Pili (fimbriae) promote attachment
  • Exotoxin A causes necrosis, blocks protein
    synthesis (? DTx)
  • P. aeruginosa is only pathogenic when introduced
    into areas of devoid normal defenses

A 48 year old Caucasian male presented to the
emergency room after a progressive history of
left foot cellulitis. The patient works as an
oil-field worker and began experiencing left foot
erythema and blisters. -- progressed to increased
erythema and a green-yellowish drainage from the
digits and in between the toes.
  • Medical history. abuse alcohol ,drug abuse when
    he was in his 20s. His family history includes
    diabetes mellitus. His x-ray report reveals no
    signs of gas in the tissue and no signs of
    osteomyelitis. His culture report revealed 3
    tiny gram negative rods and 1 gram positive
    cocci. On day 1, presumptive 4 Pseudomonas
    aeruginosa was identified. Diptheroids and
    coagulase negative staphylococcus species were
    also identified. His aerobic and anaerobic blood
    cultures were negative.In the photo on left, it
    is interesting how just his left foot is infected
    and his right foot is completely spared.
  • Discussion and Treatment
  • host does not initially appear to be
    immunocompromised. However, he has a history of
    drug use and consumes alcohol quite heavily
    during the week. His work conditions are also
    conducive to these type of infections wears
    steel toe type boots and rubber-type boots in the
    field. Soil contaminates and moisture would play
    an important role in pathogenesis of this
    infection. The patient also had exposure to
    Bactrim early in his treatment which may have
    played a role in the ability of his immune system
    to fight the infection in its early stage. Two
    extracellular proteases and extracellular protein
    toxins are produced in the initial infective
    stage. Elastin protease and alkaline protease
    destroy the cells ground substance and lysis its
    supporting structure of fibrin and elastin.
    Exotoxin A has a tissue necrotizing effect and
    has the same mechanism of action as the
    diphtheria toxin. Exoenzyme S is also thought to
    be a tissue destructive exoenzyme that is
    commonly seen during pseudomonas colonization on
    burn wounds.

The picture at left represents local colonization
of pseudomonal infection of the foot. Here, the
skin is erythematous and has a scalded-skin type
appearance. This is likely due to extracellular
toxins and proteases causing local ground
substance disruption. You can also readily see
the alginate slime layer that forms a matrix of
the pseudomonas biofilm. This alginate biofilm is
representative of pseudomonas colonization and
the bacterial attempt at protecting the colony
from host defenses. Treatment should include
primary coverage for pseudomonal infection.
Sensitivity reports revealed bacteriocidal
activity using Ciprofloxacin.
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Burkholderia pseudomallei
  • Small, motile, aerobic Gram-negative bacillus
  • Colonies are mucoid and smooth to rough and
    wrinkled in cream to orange colour.
  • Melioidosis of humans, in SE Asia and northern
  • high mortality rate if untreated
  • surgical drainage of localised infection may be
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