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MICR2209 > 18 - Opportunistic Bacterial Disease > Flashcards

18 - Opportunistic Bacterial Disease Flashcards

1
Q

True/Primary pathogens

A
  • Cause disease in healthy people
  • Relatively more virulent or pathogenic
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2
Q

Examples of primary pathogens

A
  • Bubonic plague
  • Cholera
  • Anthrax
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3
Q

Opportunistic/secondary pathogens

A
  • Infections that occur when the host immune system is weakened
  • Generally low to moderate virulence
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4
Q

1st line of innate immunity

A
  • Skin
  • Mucous membranes & secretions
  • Normal flora
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5
Q

2nd line of innate immunity

A
  • Innate immune cells
  • Inflammation
  • Complement
  • Antimicrobial substances
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6
Q

3rd line of defence

A

Adaptive immunity:
- B cells and T cells (helper and killer)

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7
Q

Drug induced disruption to innate immunity

A
  • Antibiotics disrupt normal commensal bacterial flora
  • Cancer chemotherapy disrupts immune system
  • Anti-rejection medication in organ transplant recipients suppress immune response
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8
Q

Risk factors for opportunistic infections

A

Age (neonates and elderly), Smoking, Pregnancy, Malnutrition, Obesity, Underlying disease (diabetes)

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9
Q

Characteristics of opportunistic pathogens

A
  • Typically have relatively low pathogenicity
  • Usually only cause infection in compromised hosts
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10
Q

Gram negative examples of opportunistic pathogens

A
  • Pseudomonas aeruginosa
  • Escherichia coli
  • Klebsiella pneumoniae
  • Legionella pneumophila
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11
Q

Gram positive examples of opportunistic pathogens

A
  • Staphylococcus species
  • Streptococcus pneumoniae
  • Clostridioides difficile
  • Enterococcus species
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12
Q

Opportunistic pathogen from endogenous source

A

Derived from normal human flora (e.g. gut bacteria, skin flora)

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13
Q

Opportunistic pathogen from exogenous source

A

Derived from a transient or chance encounter (e.g. hospital, water, pet)

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14
Q

Device related infections

A
  • Peripheral venous catheters are the most commonly used indwelling device in hospitalised patients
  • Device may be contaminated during insertion
  • Staphylococcus epidermidis is the leading cause
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15
Q

Staphylococcus epidermidis

A
  • Ubiquitous commensal skin organism
  • Relatively low virulence
  • Produces only limited toxins
  • Ability to cause infection associated with adherence to plastic and production of biofilm
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16
Q

Disruption of skin barrier

A
  • Intact skin is a major defence against infection
  • Disruption of the host/environment barrier allows organisms to access deeper tissue or blood
17
Q

Disruption of commensal flora

A
  • Antibiotics are a major cause of microbiome disruption
  • Altered commensal flora allows opportunistic pathogens to flourish
18
Q

Clostridioides difficile

A
  • Gram positive
  • Endospore forming rod
  • Strict anaerobe
  • motile via flagella
  • Ubiquitous in soil & water
  • Endospores regarded as major mode of transmission
  • Cause of antibiotic associated diarrhoea
19
Q

Immune disruption

A
  • Medicines can weaken the immune response
    (e.g. chemotherapy, corticosteroids, anti-rejection drugs)
  • Recent infection also alters immune response
20
Q

Cancer chemotherapy

A
  • Chemotherapy reduces neutrophils (neutropenia)
  • Additional risk factor through catheters
  • Pathogens include Staphylococci, Streptococci, Enterobacteriaceae and Pseudomonas
21
Q

Escherichia coli

A
  • Gram negative rods, facultative aerobe
  • Member of the Enterobacteriaceae
  • Motile by flagella
  • Normal component of gut flora
  • Endogenous source of infection
  • Organism in GI tract can gain access to bloodstream via damaged epithelia
22
Q

Recent viral infection

A
  • Disrupts the immune response (may also damage epithelia)
  • Bacterial pneumonia is a very common, community acquired opportunistic infection
23
Q

Streptococcus pneumoniae

A
  • Major cause of pneumonia
  • Gram positive cocci, facultative aerobe
  • Normally founds in pairs, non-motile
  • Normal component of upper respiratory tract flora (endogenous source of infection)
  • Capsular polysaccharide allows evasion of host immune cells

MICR2209 (26 decks)

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