MICR 4053 Exam 3
Opportunistic pathogen ANS: Typically non-pathogenic microorganisms that act as a pathogen in certain
circumstances
What 4 surface components facilitate attachment? ANS: 1) Flagella
2) pili
3) lipopolysaccharide (LPS)
4) alginate
Pseudomonas: Virulence factors - what are they, what do they do ANS: 1) Flagella: surface component
to facilitate adherence, mediates motility in P. aeruginosa
2) Pili: surface component to facilitate adherence, mediates motility in P. aeruginosa
3) Lipid A (LPS): responsible for endotoxin activity
4) Alginate: mucoid exopolysaccharide that forms a prominent capsule on the bacterial surface and
protects the organism from phagocytosis and antiobiotic killing. Also promotes adherence.
5) Exotoxin A: one of the most important virulence factors produced by pathogenic strains of P.
aeruginosa.
a) Disrupts protein synthesis by blocking peptide chain elongation in eukaryotic cells
b) Contributes to the dermatonecrosis that occurs in burn wounds, corneal damage in ocular infections,
and tissue damage in chronic pulmonary infections
6) Pyocyanin: a blue pigment produced by P. aeruginosa catalyzes the production of superoxide and
hydrogen peroxide, toxic forms of oxygen. It also stimulates interleukin-8 (IL-8) release, leading to
enhanced attraction to neutrophils.
7) Pyoverdine: (a yellow-green pigment) is a siderophore that binds iron for use in metabolism. It also
regulates secretion of other virulence factors including ETA.
8) Phospholipase C: is a heat-labile hemolysin that breaks down lipids and lecithin, facilitating tissue
destruction.
9) Elastase (LasA, LasB): act synergistically to degrade elastin, resulting in damage to elastin-containing
tissue
,10) Alkaline Protease: contributes to tissue destruction and spread of P. aeruginosa. It also interferes
with the host immune response
11) Exoenzyme S: (and T) are extracellular toxins produced by P. aeruginosa. ExoS and ExoT are secreted
by a type III secretion system.
What makes Pseudomonas resistant to many antibiotics? ANS: 1) Mutation of porin proteins constitutes
the major mechanism of resistance
2) Produces many different Beta-lactamases that can inactivate many Beta-lactam antibiotics
What factors predispose immunocompromised patients to Pseudomonas infection? ANS: 1) Previous
therapy with broad-spectrum antiobiotics that eliminate the normal, protective bacterial population
2) Use of mechanical ventilation equipment, which may introduce the organism to the lower airways
What kind of infections can Pseudomonas cause? ANS: 1) Pulmonary infections: usually the lower
respiratory tract, can range in severity from asymptomatic colonization or benign inflammation of the
bronchials to severe necrotizing bronchopneumonia.
2) Burn wound infections: are common- moist surface of the burn and inability of neutrophils to
penetrate into the wounds predispose patients to such infections. Colonization of the burn wound,
followed by localized vascular damage, tissue necrosis, and ultimately bacteremia, is common in
patients with severe burns
3) Folliculitis: is another common infection caused by Pseudomonas, resulting from immersion in
contaminated water (e.g., hot tubs, whirlpools, swimming pools)
4) Fingernail infections: people whose hands are frequently exposed to water or frequent "nail salons"
5) Osteochondritis: inflammation of bone and cartilage of the foot after a penetrating injury
6) Urinary tract infections: occur in patients with long-term indwelling urinary catheters. Patients are
treated with multiple courses of antibiotics, which select for the more resistant strains of bacteria, such
as Pseudomonas
7) External otitis: frequently caused by P. aeruginosa, with swimming an important risk factor
(swimmers ear)
8) Malignant external otitis: is a virulent form of disease seen primarily in persons with diabetes and
elderly patients
, 9) Infections of the eye: occur after initial trauma to the cornea, and then exposure to P. aerufinosa in
contaminated water. Corneal ulcers develop and can progress to rapidly progressive, eye-threatening
disease
Why is mortality rate in affected patients higher with P. aeruginosa bacteremia? ANS: 1) The
predilection of the organism for immunocompromised patients
2) Difficulty in treating antibiotic-resistant strains
3) The inherent virulence of Pseudomonas
What are 3 features for members of the Campylobacter family? ANS: 1) Spiral, gram-negative rods with
a low DNA guanine plus cytosine base ratio
2) An inability to ferment or oxidize carbohydrates
3) Microaerophilic growth requirements (i.e., growth only in the presence of reduced oxygen level)
Reservoir and types of infections (symptoms) caused by C. jejuni, C. coli and C. fetus ANS: 1) C. jejuni:
(reservoir: poultry, cattle, sheep) infection causes gastroenteritis, extraintestinal infections, Guillain-
Barre syndrome, reactive arthritis
2) C. coli: (reservoir: pigs, poultry, sheep, birds) infection causes gastroenteritis, extraintestinal
infections
3) C. fetus: (reservoir: cattle, sheep) infection causes vascular infections (e.g., septicemia, septic
thrombophlebitis, endocarditis), meningoencephalitis, gastroenteritis
What is Guillain-Barré syndrome? What causes it? ANS: 1) Believed to be an autoimmune disease
caused by antigenic cross-reactivity between oligosaccharides in bacterial capsule and
glycosphingolipids on surface of neural tissues
2) Antibiotics directed against specific strains of Campylobacter can damage neural tissue in the
peripheral nervous system
Mechanism of transmission of Campylobacter ANS: 1) Zoonotic infection; improperly prepared poultry
is a common source of human infections
Opportunistic pathogen ANS: Typically non-pathogenic microorganisms that act as a pathogen in certain
circumstances
What 4 surface components facilitate attachment? ANS: 1) Flagella
2) pili
3) lipopolysaccharide (LPS)
4) alginate
Pseudomonas: Virulence factors - what are they, what do they do ANS: 1) Flagella: surface component
to facilitate adherence, mediates motility in P. aeruginosa
2) Pili: surface component to facilitate adherence, mediates motility in P. aeruginosa
3) Lipid A (LPS): responsible for endotoxin activity
4) Alginate: mucoid exopolysaccharide that forms a prominent capsule on the bacterial surface and
protects the organism from phagocytosis and antiobiotic killing. Also promotes adherence.
5) Exotoxin A: one of the most important virulence factors produced by pathogenic strains of P.
aeruginosa.
a) Disrupts protein synthesis by blocking peptide chain elongation in eukaryotic cells
b) Contributes to the dermatonecrosis that occurs in burn wounds, corneal damage in ocular infections,
and tissue damage in chronic pulmonary infections
6) Pyocyanin: a blue pigment produced by P. aeruginosa catalyzes the production of superoxide and
hydrogen peroxide, toxic forms of oxygen. It also stimulates interleukin-8 (IL-8) release, leading to
enhanced attraction to neutrophils.
7) Pyoverdine: (a yellow-green pigment) is a siderophore that binds iron for use in metabolism. It also
regulates secretion of other virulence factors including ETA.
8) Phospholipase C: is a heat-labile hemolysin that breaks down lipids and lecithin, facilitating tissue
destruction.
9) Elastase (LasA, LasB): act synergistically to degrade elastin, resulting in damage to elastin-containing
tissue
,10) Alkaline Protease: contributes to tissue destruction and spread of P. aeruginosa. It also interferes
with the host immune response
11) Exoenzyme S: (and T) are extracellular toxins produced by P. aeruginosa. ExoS and ExoT are secreted
by a type III secretion system.
What makes Pseudomonas resistant to many antibiotics? ANS: 1) Mutation of porin proteins constitutes
the major mechanism of resistance
2) Produces many different Beta-lactamases that can inactivate many Beta-lactam antibiotics
What factors predispose immunocompromised patients to Pseudomonas infection? ANS: 1) Previous
therapy with broad-spectrum antiobiotics that eliminate the normal, protective bacterial population
2) Use of mechanical ventilation equipment, which may introduce the organism to the lower airways
What kind of infections can Pseudomonas cause? ANS: 1) Pulmonary infections: usually the lower
respiratory tract, can range in severity from asymptomatic colonization or benign inflammation of the
bronchials to severe necrotizing bronchopneumonia.
2) Burn wound infections: are common- moist surface of the burn and inability of neutrophils to
penetrate into the wounds predispose patients to such infections. Colonization of the burn wound,
followed by localized vascular damage, tissue necrosis, and ultimately bacteremia, is common in
patients with severe burns
3) Folliculitis: is another common infection caused by Pseudomonas, resulting from immersion in
contaminated water (e.g., hot tubs, whirlpools, swimming pools)
4) Fingernail infections: people whose hands are frequently exposed to water or frequent "nail salons"
5) Osteochondritis: inflammation of bone and cartilage of the foot after a penetrating injury
6) Urinary tract infections: occur in patients with long-term indwelling urinary catheters. Patients are
treated with multiple courses of antibiotics, which select for the more resistant strains of bacteria, such
as Pseudomonas
7) External otitis: frequently caused by P. aeruginosa, with swimming an important risk factor
(swimmers ear)
8) Malignant external otitis: is a virulent form of disease seen primarily in persons with diabetes and
elderly patients
, 9) Infections of the eye: occur after initial trauma to the cornea, and then exposure to P. aerufinosa in
contaminated water. Corneal ulcers develop and can progress to rapidly progressive, eye-threatening
disease
Why is mortality rate in affected patients higher with P. aeruginosa bacteremia? ANS: 1) The
predilection of the organism for immunocompromised patients
2) Difficulty in treating antibiotic-resistant strains
3) The inherent virulence of Pseudomonas
What are 3 features for members of the Campylobacter family? ANS: 1) Spiral, gram-negative rods with
a low DNA guanine plus cytosine base ratio
2) An inability to ferment or oxidize carbohydrates
3) Microaerophilic growth requirements (i.e., growth only in the presence of reduced oxygen level)
Reservoir and types of infections (symptoms) caused by C. jejuni, C. coli and C. fetus ANS: 1) C. jejuni:
(reservoir: poultry, cattle, sheep) infection causes gastroenteritis, extraintestinal infections, Guillain-
Barre syndrome, reactive arthritis
2) C. coli: (reservoir: pigs, poultry, sheep, birds) infection causes gastroenteritis, extraintestinal
infections
3) C. fetus: (reservoir: cattle, sheep) infection causes vascular infections (e.g., septicemia, septic
thrombophlebitis, endocarditis), meningoencephalitis, gastroenteritis
What is Guillain-Barré syndrome? What causes it? ANS: 1) Believed to be an autoimmune disease
caused by antigenic cross-reactivity between oligosaccharides in bacterial capsule and
glycosphingolipids on surface of neural tissues
2) Antibiotics directed against specific strains of Campylobacter can damage neural tissue in the
peripheral nervous system
Mechanism of transmission of Campylobacter ANS: 1) Zoonotic infection; improperly prepared poultry
is a common source of human infections
