“MDR-Pseudomonas: Another
Horse of the Apocalypse”
Jeanette Harris MS, MSM, MT(ASCP), CIC
MultiCare Health System
Tacoma, WA
MultiCare Infection
Prevention team
Jeanette
with
Marcia,
Steve, Sue,
Stacia and Roxy
Pseudomonas sp.
• ''Pseudomonad'' = 'false unit'
– Greek pseudo (ψευδο 'false') and monas
(μονάς / μονάδα 'a single unit')
– "monad" was used in the early history of
microbiology = single-celled organisms
– First described 1894
– Gram-negative, rod-shaped and polar-flagella
bacteria.
– Pseudomonas aeruginosa is the type species
of its group contains 12 other members
Pseudomonas aeruginosa
• Free-living bacterium, found in soil and water
• Occurs regularly on the surfaces of plants
and animals
• Genus is well known to plant microbiologists groups of bacteria that are plant pathogens
• Emerging opportunistic pathogen of clinical
relevance
• Epidemiological nosocomial transmission
• Antibiotic resistance is increasing in clinical
isolates.
Pseudomonas aeruginosa
• Epitome of an opportunistic pathogen of humans
• Never infects uncompromised tissue
– there is hardly any tissue that it cannot infect if the
tissue defenses are compromised in some manner
• Causes urinary tract infections, respiratory system
infections, dermatitis, soft tissue infections,
bacteremia, bone and joint infections,
gastrointestinal infections and a variety of
systemic infections, particularly in patients with
severe burns and in cancer and AIDS patients
who are immunosuppressed.
• Serious problem in patients hospitalized with
cancer, cystic fibrosis, and burns
• The case fatality near 50 percent
Pseudomonas aeruginosa
• Primarily a nosocomial pathogen
• Overall incidence of P. aeruginosa
infections in U.S. hospitals averages about
0.4 percent (4 per 1000 discharges)
• Fourth most commonly-isolated
nosocomial pathogen accounting for 10.1
percent of all hospital-acquired infections*
*CDC
Pseudomonas aeruginosa
• Ubiquitous in soil and water
• On surfaces in contact with soil or water
• Metabolism is respiratory and never
fermentative
• But it will grow in the absence of O2 if NO3
is available as a respiratory electron
acceptor.
Pseudomonas aeruginosa
• In nature might be found in a biofilm,
attached to some surface or substrate, or
in a planktonic form, as a unicellular
organism, actively swimming by means of
its flagellum
• The most vigorous, fast-swimming
bacteria seen in hay infusions and pond
water samples
• Do you have a hot tub? Swimming pool?
Pseudomonas aeruginosa
• Very simple nutritional requirements
• Observed "growing in distilled water",
which is evidence of its minimal nutritional
needs
• In the laboratory, the simplest medium for
growth of Pseudomonas aeruginosa
consists of acetate as a source of carbon
and ammonium sulfate as a source of
nitrogen
Pseudomonas aeruginosa
• Organic growth factors are not required, can use more than
seventy-five organic compounds for growth
• Optimum temperature for growth is 37 degrees, able to grow
at temperatures as high as 42 degrees
• Resistant to high concentrations of salts and dyes, weak
antiseptics, and many commonly used antibiotics
• Predilection for growth in moist environments, reflection of its
natural existence in soil and water
• Contribute to success as an opportunistic pathogen
• May produce three colony type
– Natural isolates from soil or water - small, rough colony
– Clinical samples
• Tissue - smooth colony type
• Respiratory and urinary tract secretions - mucoid attributed to the
production of alginate slime
• smooth and mucoid colonies are presumed to play a role in colonization
and virulence.
Capable of growing in diesel and jet fuel---WILL be a part of the oil spill
P. aeruginosa
• Two types of soluble pigments
– Pyoverdin = Fluorescent pigment
– Pyocyanin = blue pigment
• produced abundantly in media of low-iron content
and functions in iron metabolism
• (from "pyocyaneus") refers to "blue pus", which is
a characteristic of suppurative infections
Pyocyanin = Blue Pigment
• Impairs the normal function of human
nasal cilia, disrupts the respiratory
epithelium, and exerts a proinflammatory
effect on phagocytes
• plays a role in invasion if it extracts iron
from the host for bacterial growth in a
relatively iron-limited environment
Resistance to Antibiotics
• Notorious for resistance to antibiotics
• Naturally resistant to many antibiotics due to permabiliity
barrier Gram-negative outer membrane
• Biofilm form makes the cells impervious to therapeutic
concentrations antibiotics
• Lives with actinomycetes and molds – acquired resistance to
naturally occurring antibiotics
• Maintains antibiotic resistance plasmids, both R-factors and
RTFs, and it is able to transfer these genes by means of the
bacterial mechanisms of horizontal gene transfer (HGT),
mainly transduction and conjugation
• Few antibiotics are effective
– Fluoroquinolones, gentamicin and imipenem
– Cystic fibrosis - so resistant that it cannot be treated
Pathogenesis
• Opportunistic pathogen
– disease process begins with some alteration or
circumvention of normal host defenses
– Multifactorial - wide array of virulence
determinants possessed by the bacterium
– Include septicemia, urinary tract infections,
pneumonia, chronic lung infections, endocarditis,
dermatitis, and osteochondritis
• Invasive and toxinogenic
– Three distinct stages
• bacterial attachment and colonization
• local invasion
• disseminated systemic disease
Colonization
• Part of the normal flora of humans
– healthy individuals outside the hospital is relatively low (024%)
• Pili adhere to epithelial cells of upper respiratory tract
• Adhesins bind to specific galactose or mannose or
sialic acid receptors on epithelial cells
• Respiratory tract requires pili adherence and
production of a protease enzyme that degrades
fibronectin in order to expose the underlying pilus
receptors on the epithelial cell surface
• Tissue injury plays a role in colonization of the
respiratory tract
– +Adhere to tracheal epithelial cells infected with influenza
virus
Invasion
• Production of extracellular enzyme toxins
break down barriers and damage host cells,
as well as resistance to phagocytosis and the
host immune defenses
• Bacterial capsule or slime layer protects
bacteria from opsonization by antibodies,
complement deposition, and phagocyte
engulfment
• Extracellular proteases provide virulence at
the invasive stage
– elastase and alkaline protease
– a cytotoxin (mw 25 kDa) and two hemolysins
Toxinogenesis-2
• Exoenzyme S
– produced by bacteria growing in burned tissue and may be
detected in the blood before the bacteria are
– may act to impair the function of phagocytic cells in the
bloodstream and internal organs as a preparation for invasion by
P. aeruginosa.
•
Exotoxin A (Similar to diphtheria toxin)
– enters cells in the same manner and has the exact enzymatic
mechanism
– local and systemic disease processes
– necrotizing activity at the site of bacterial colonization
– toxinogenic strains cause a more virulent form of pneumonia
than nontoxinogenic strains
– purified Exotoxin A is highly lethal for animals including primates
Cell-to-Cell Signaling
• They TALK to each other!
• Sense their own cell density
• Behave as a population instead of
individual cells
• Express specific genes as a population
instead of individual cells
• Think of the Borg from Star Trek
Diseases
•
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Endocarditis
Respiratory infections
Bacteremia and septicemia
Central nervous system infections
Ear infections including external otitis
Eye infections
Bone and joint infections
Urinary tract infections
Gastrointestinal infections
Skin and soft tissue infections, including
wound infections, pyoderma and dermatitis
Host Defenses
• Killing is most efficient in the presence of
type-specific opsonizing antibodies
• Phagocytosis plus opsonizing antibody is
principal functional
• Once infection is established, other
antibodies, such as antitoxin is important
• Cystic fibrosis is the exception
Epidemiology and Control
• Found EVERYWHERE
• Hospital:
– disinfectants, respiratory equipment, food,
sinks, taps, toilets, showers and mops
– fruits, plants, vegetables, visitors, patients
transferred from other facilities
– patient to patient on the hands of hospital
personnel, by direct patient contact with
contaminated reservoirs, and by the ingestion
of contaminated foods and water
Control
• Isolation procedures, aseptic technique,
and careful cleaning and monitoring of
respirators, catheters, and other
instruments
• Topical therapy of burn wounds with
antibacterial agents such as silver
sulfadiazine, coupled with surgical
debridement
Patterns
Event: 11.8 times
higher incidence of
Hospital
Pseudomonas
aeruginosa
Respiratory
Isolates from ICU.
Active period (3
months) compared to
base line period (9
months)
*^&%$#@$%^((((*%###%!!!!!!
What we did
1.
2.
3.
4.
Switch to sterile water for feeding tubes
BLEACH for cleaning
Staff Education
Check for sources of moisture
contamination
5. Inspection of unit - guess what we found
6. “What’s different?”
7. Should we just nuke the rooms?
How it worked
Not ZERO….but MUCH better
What’s next?
Pseudomonas bioremediation was used was the Exxon Valdez Oil Spill
…..remember, Pseudomonas eats EVERYTHING!
Crude Oil = Carbon + Hydrogen
• Pseudomonas can use over 100
different molecules as carbon
sources, including proteins, fats,
carbohydrates, and hydrocarbons
• Found in carbon dioxide and
organic compounds.
Hydrogen
•Together with oxygen, essential
to all aspects of cell
Clean-up crews use the
Pseudomonas putida
bacteria to decontaminate
soil polluted by oil spills.
So….Maybe there’s some good
news after all