Microbial Infection Flashcards

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1
Q

What does the innate immune system consist of?

A

Normal Microbiota, Physical barriers, chemical barriers and phagocytic cells

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2
Q

What is normal mircobiota and how does it offer protection?

A

These are the cells that live on the body. They offer protection by competing with other pathogens for colonisation sites. They may produce toxins to inhibit other micro-organisms. They may alter the pH making it an uninhabitable space for other micro-organisms.

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3
Q

Describe what the physical barriers are and how they offer protection

A

Skin - secrets sebum and fatty acids that reduce the pH and inhibit growth
Mucomuciliary clearance - Particals settle on stick mucus of respiratory tract epithelium. Debris is transported by cilia to oropharynx where it is swallowed. Low pH of stomach kills bacteria.
Flushing - i,e, of the urinary tract
Peristalsis - GI tract, prevents bacteria from becoming stationary

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4
Q

Describe what the chemical barriers are and how they offer protections

A

Mucus - antigenic structure
Antimicrobial proteins - Lysozyme, lactoferrin, Defensins
Gastric Acid
Plasma proteins - Complement, C-reactive protein (CRP), Mannose-binding lectin (MBL)
Transferrin

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5
Q

Name some phagocytes

A

Macrophages, Neutrophils
Monocytes
dendritic cells
Mast cells

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6
Q

Define Commensal

A

Micro-organsim which forms part of the hosts normal microbiota

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7
Q

Define pathogen

A

Micro-organism capable of causing an infection

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8
Q

Define virulence

A

Measure of the damage a pathogen causes to the host

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9
Q

What are the three types of pathogens?

A

Oligate - always associated with disease
Conditional - may cause disease if certain conditions are met
Opportunistic - Only infects hosts that are immunocompromised

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10
Q

Describe the steps on infection

A
Recognition, 
attachment and entery
multiplication
evasion of host defences
shedding
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11
Q

How are infections established in healthy hosts?

A
  1. microbes attach and penetrate host body surfaces
  2. microbes introduces into hosts by biting arthropods
  3. Microbes introduced via skin wounds or animal
  4. Microbes introduced when host defences are down
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12
Q

What is tissue tropism and the factors that affect tissue tropism?

A
The microbes affinity for a specific tissue. Hosts can have broad tissue tropism .
Factors that influence tissue tropism;
Cell receptors,
pH
Transcription factors
Local temperature
Barriers
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13
Q

Where does the influenza virus attach?

A

Cilia and microvili on trachea epithelium

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14
Q

Where does vibrio cholerae attach?

A

Villi of intestinal epithelium

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15
Q

Where does helicobacter pylori attach?

A

Gastric Mucosa

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16
Q

What affects virulence?

A
Toxigenesis
Antibiotic resistance
Pilus formation
Capsule
Iron transport systems
Adhesion factors
Enzymes involved with breaking down host materials
17
Q

Describe features of bacterial endotoxins

A

low toxicity, Part of Gram neg wall, lipopolysaccharides and they have a low specificity

18
Q

Describe some features of bacterial exotoxins

A

Highly toxic, produces in both Gram pos and neg, can be converted into toxoids for vaccines

19
Q

Name some important examples of antibiotic resistant diseases

A

Meticillin resistant staphylococcus aureus (MRSA)
Vancomysin resistant staphylococcus aureus (VRSA)
Multi-resistant mycobacterium tuberculosis
HIV
Malaria

20
Q

Nam the three factors transmission relays on

A

Number of microorganisms spread, number required to infect host, their stability in environment

21
Q

What is animal to human transmission called? Give some examples

A
Zoonoses, this can be via invertebrates (arthropods - malaria and yellow fever, Shellfish - hepatitis A and cholera)
Via vertebrates (mammals -rabies and tape worm, Birds - salmonella)
22
Q

What is fomite transmission?

A

Transmission via inanimate objects

23
Q

What are nosocomial infections?

A

Infections acquired in a hospital stay

24
Q

Name the types of human to human transmission

A

Respiratory/salivary
Fecal-oral
Venereal spread