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Infection and Immunity > Week 5 - Infections on Surfaces > Flashcards

Week 5 - Infections on Surfaces Flashcards

1
Q

State examples of normal mucosal flora present in the eye.

A
  1. Coagulase negative staphylococci
  2. Diptheroids
  3. Saprophytic Neisseria species
  4. Viridans group streptococci
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2
Q

State examples of normal mucosal flora present in the nares.

A

Staphylococcus aureus

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3
Q

State examples of normal mucosal flora present in the nasopharynx.

A

Streptococcus pneumonia, Neisseria meningitidis, Haemophilus influenzae

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4
Q

State examples of normal mucosal flora present in the mouth.

A

Viridans streptococci, Neisseria, Veillonella, Lactobacillus, Actinomyces, Bacteroides, Capnocytophaga, Eikenella, Prevotella, Fusobacteria, Clostridia, Propionibacteria, Candida, Geotrichium species

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5
Q

State examples of normal mucosal flora present in the stomach.

A

Helicobacter, Streptococci, Staphylococci, Lactobacilli

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6
Q

State examples of normal mucosal flora present in the intestine.

A

Bacteroides, Bifidobacterium, Eubacterium, Lactobacillus, Coliforms, Aerobic and anaerobic streptococci, Clostridium, yeasts

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7
Q

State examples of normal mucosal flora present in the urethra.

A

Enterobacteriaceae, lactobacilli, diptheroids, alpha and non-haemolytic streptococci, enterococci

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8
Q

State examples of normal mucosal flora present in the vagina.

A

Lactobacilli, diptheroids, micrococci, coagulase-negative staphylococci, enterococcus faecalis, microaerophilic and anaerobic streptococci, Mycoplasmas, ureaplasmas, yeast

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9
Q

What is the microbiota?

A

Microorganisms carried on the skin or mucosal surfaces that are typically harmless or even beneficial

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10
Q

State the ways in which an individual can become infected.

A
  1. Invasion, e.g. Strep pyogenes pharyngitis
  2. Migration, e.g. E. coli urinary tract infections
  3. Innoculation, e.g. coagulase negative staphylococcus prosthetic joint infections
  4. Haematogenous, e.g. viridans strep endocarditis
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11
Q

State some examples of external natural surface infections.

A
  1. Cellulitis
  2. Conjunctivitis
  3. Pharyngitis
  4. Gastroenteritis
  5. Pneumonia
  6. Urinary tract infections
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12
Q

State some examples of internal natural surface infections.

A
  1. Endovascular: endocarditis, vasculitis
  2. Osteomyelitis
  3. Empyema
  4. Septic arthritis
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13
Q

Define empyema.

A

Collection of pus in the pleural cavity

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14
Q

State the organisms commonly implicated in native endocarditis/prosthetic valve endocarditis > 1 year post-operation.

A
  1. Candida
  2. HACEK Group
  3. Viridans streptococci
  4. Enterococcus faecalis
  5. Staphylococcus aureus
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15
Q

State the organisms commonly implicated in prosthetic valve endocarditis < 1 year post-operation.

A

Coagulase-negative staphylococci

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16
Q

State the organisms commonly implicated in prosthetic joint infections.

A
  1. Coagulase-negative staphylococci

2. Staphylococcus aureus

17
Q

State the organisms commonly implicated in cardiac pacing wire endocarditis.

A
  1. Coagulase-negative staphylococci

2. Staphylococcus aureus

18
Q

Outline the processes involved in pathogenesis of infection at surfaces.

A
  1. Adherence to host cells/prosthetic surfaces
  2. Biofilm formation
  3. Invasion and multiplication
  4. Host response:
    - Pyogenic: neutrophils –> pus
    - Granulomatous: fibroblasts, lymphocytes, macrophages –> nodular inflammatory lesions
19
Q

Which bacterial structures enable adherence to host cell membranes?

A
  1. Pili

2. Fimbriae

20
Q

What substance when exposed in damaged heart valves is ideal for colonisation by virulent bacteria?

A

Fibronectin

21
Q

How are bacteria in biofilms different from free-living vegetative bacteria?

A
  1. Much slower turnover
  2. Longer lifecycle
  3. Smaller in size
22
Q

Outline the stages involved in biofilm formation.

A
  1. Starvation can induce bacteria to shrink and adopt a spore-like state known as ultramicrobacteria, which wait in water, soil, rock or tissue until conditions are suitable for favourable growth.
  2. Active bacteria can attach to almost any surface. Changes in gene expression transform “swimmers” to “stickers” within minutes.
  3. Attached bacteria multiply and encase the colonies with a slimy matrix.
  4. Nutrients diffuse into the matrix.
  5. Close proximity of cells in the matrix facilitates the exchange of molecular signals that regulate behaviour
  6. Chemical gradients create microenvironments for different microbial species or levels of activity
  7. Although antimicrobials damage outer cell layers, the biofilm community is resistant
  8. Propelled by shear forces, aggregated cells can become detached or roll or ripple along a surface in sheets and remain in their protected biofilm state
23
Q

State examples of prosthetic surfaces that can become infected.

A
  1. Peritoneal dialysis catheters
  2. Endovascular grafts
  3. Pacing wires
  4. Cardiac valves
  5. Intravascular lines
  6. Prosthetic joints
  7. Ventriculo-peritoneal shunts
24
Q

State the controls involved in biofilm formation.

A
  1. Biofilm formation
  2. Sporulation
  3. Virulence factor secretion
25
Q

Outline the three principles of biofilm formation.

A
  1. Signalling molecules - autoinducers (AI)
  2. Cell surface or cytoplasmic receptors
  3. Gene expression: co-operative behaviours and more AI production
26
Q

Outline the types of virulence factors.

A
  1. Exotoxins: enzymes, superantigens, AB toxins, cytolytic

2. Endotoxins

27
Q

Outline the main steps involved in establishing infection.

A
  1. Exposure
  2. Adherence
  3. Invasion
  4. Multiplication
  5. Dissemination
28
Q

Outline the main principles of management of infection.

A
  1. Identify infecting organism and its antimicrobial susceptibilities
  2. Blood culture
  3. Prosthetic device/tissue sonication and culture
  4. Sterilise tissue and reduce bioburden
  5. Antibacterials
  6. Remove prosthetic material
  7. Surgery - resect infected material
29
Q

What are the challenges of treating infection?

A
  1. Adherent organisms
  2. Low metabolic state of biofilm microorganisms/small colony variants
  3. Dangers/difficulties of surgery
  4. Poor antibiotic penetration into biofilms
30
Q

Outline the principles of prevention for natural surface infection.

A
  1. Maintain surface integrity
  2. Prevent bacterial surface colonisation
  3. Remove colonising bacteria
31
Q

Outline the principles of prevention for prosthetic surface infection.

A
  1. Prevent contamination
  2. Inhibit surface colonisation
  3. Remove colonising bacteria

Infection and Immunity (2 decks)

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