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Microbes > Module 4 - Microbes as Pathogens > Flashcards

Module 4 - Microbes as Pathogens Flashcards

1
Q

Name 4 key ways in which the microbiota help in defence against pathogens

A
  1. Cover every surface so less room for pathogens
  2. Some produce antibiotics
  3. Compete with pathogens for resources
  4. Role in digestion + help immune system
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2
Q

Name the three areas of the human body where most microbiota are found

A
  1. GI Tract
  2. Skin
  3. Mouth/nasopharynx
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3
Q

How is the gut microbiota initially acquired?

A

On passage through the birth canal

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4
Q

What change marks the transition to a more stable adult gut microbiota

A

The introduction of solid food

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5
Q

What is the only significant normal flora bacteria? (And what ailment is more common in people who have this?)

A

Heliobacter pylori (gastric ulcer)

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6
Q

What type of bacteria are most common in the colon (in terms of oxygen requirements)

A

Obligate anaerobes

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7
Q

What difference was found between normal mice and “germ free” mice with no microbiota?

A

Normal mice consume less food, but have 42% MORE body fat (better absorption)

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8
Q

What is dysbiosis?

A

A disruption of the normal gut flora, which is associated with disease

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9
Q

Name the opportunistic pathogen which is found in the soil and can affect burn patients

A

Pseudomonas aeuginosa

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10
Q

Name the opportunistic pathogen which can colonise intraveous catheters

A

Staphylococcus epidermidis

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11
Q

Name the opportunistic pathogen which causes meningitis, and where it is normally found

A

Neisseria meningitidis -> nasopharynx

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12
Q

What key symptom does Mycrobacterium tuberculosis (TB) cause in the body?

A

Ghon complexes (granulomas of caseous necrotic tissue, including dead and dying macrophages)

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13
Q

Describe the structure of Treopnema pallidum, the disease they cause and the three phases of the disease

A

Flexible, helical bacteria; syphilis; Primary lesion, secondary (spread) and latent phase

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14
Q

Name the 4 steps of Koch’s Postulates (and what this actually means)

A

Way to prove that a particular microbe causes a particular disease:
1. Organism found in lesion
2. Grow organism outside the body in lab
3. Organism must reproduce the disease
4. Re-isolate from test animal

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15
Q

Name three examples of problems with carrying out Koch’s Postulates

A
  1. Cannot grow cultures in lab media for some microbes (e.g., Mycbacterium leprae)
  2. Ethical problems (e.g., AIDS, Ebola)
  3. No suitable animal model, e.g., gonorrhoea)
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16
Q

What are the two metrics by which virulence can be measured?

A

Minimum infectious dose and LD50

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17
Q

Name two examples of virulence determinants in some bacteria

A

Capsule (often poly-D-glutamic acid) to inhibit phagocytosis
Toxins (suppress initially, then lethal)

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18
Q

Name the 4 stages of the infection process

A

Exposure - Adherence - Invasion - Multiplication

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19
Q

Name the 2(3?) stages of the disease process

A

Toxicity//Invasiveness -> Tissue or Systemic Damage

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20
Q

What is the difference between how commensal and pathogenic E. coli adhere to the host?

A

Commensal: attach by Type 1 peritrichous fimbriae (carrying a protein H tip adhesin) to mannose receptors on epithelial cells

Pathogenic: use CFA (colonisation factor antigen) fimbriae to attach to duodenal mucosa and release toxins

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21
Q

Give an example of non-fimbrial adhesion (species and mechanism)

A

S. pyogenes -> binds to respiratory tract epithelial cells using M PROTEIN (causes sore throat + rheumatic fever)

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22
Q

What is the difference between localised and systemic infection?

A

Systemic - gets into bloodstream
Localised - only affects one organ or body part

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23
Q

What are toxins (basic defintion)?

A

Simple soluble proteins (often enzymes) which are extracellular, rapidly transported in the body, and cause damage to the host

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24
Q

Name and give one example of the 3 main types of exotoxins

A

Enterotoxin (e.g., cholera toxin)
Cytotoxin (e.g., haemolysin of C. perfringens)
Neurotoxin (e.g., botulinium toxin)

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25
Q

What do enterotoxins do?

A

Stimulate GI tract cells in an abnormal way, eliciting profuse fluid secretion (dehydration)

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26
Q

What do Cytotoxins do?

A

Kill cells by enzymatic attack

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27
Q

What are the two main types of cytotoxins?

A

1 - Those that bind to cholestrol in membranes of host cells, forming pores -> ß-haemolysis
2 - Phospholipase enzymes

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28
Q

What do neurotoxins do?

A

Interfere with normal transmission of nerve impulses

29
Q

What is the structure and function of the botulinum toxin?

A

A-B toxin (heavy and a light chain linked by disulphide bond) -> heavy chain binds to glycoprotein receptor on neurons, so light chain (A) can enter nerve cell

30
Q

How does botulinum toxin cause flaccid paralysis?

A

Light chain Zinc Metalloprotease inhibits release of neurotransmitter Acetylcholine, preventing muscle contraction

31
Q

What enzyme does the cholera toxin activate inside the cell (and how does this lead to fluid loss)?

A

Epithelial adenylate cyclase, blocks Na+ movement -> water movement into lumen

32
Q

What are Endotoxins (and what is the main example)?

A

Heat-stable lipopolysaccharides embedded in the outer membrane of Gram-negative bacteria (LIPID A)

33
Q

What are the three main effects of Lipid A (and what symptoms do these cause)?

A
  1. Activates Monocytes -> fever
  2. Activates Complement Cascade -> permeabilisiation of blood vessels
  3. Activates coagulation cascade -> vascular coagulation
34
Q

What structural element of Lipid A can vary (and how does this affect its toxicity)?

A

The length and number of fatty acyl chains (more and shorter = higher toxicity)

35
Q

How does Lipid A actually spread in the host?

A

Vesicles containing Lipid A “bleb” off from bacteria into host tissue and shed into bloodstream

36
Q

Name 4 modes of transmission for viral diseases (and most common one?)

A

Inhalation (MOST COMMON); ingestion; inoculation; congenital

37
Q

Name 4 modes of laboratory diagnosis of viral diseases (and least viable for population-wide)

A

Whole virus (least viable); viral antigen, viral nucleic acid; specific antibody response

38
Q

State the structure and genome type of the Picornavirus family (e.g. HepA)

A

Small, ssRNA, icosahedral, naked viruses

39
Q

Name the 4 genuses of Picornavirus (and the most common syndrome of each)

A

Enterovirus (CNS e.g., polio)
Hepatovirus (HepA)
Rhinovirus (Colds)
Aphthovirus (Foot and Mouth)

40
Q

State how Polio is spread + symptoms

A

Faecal-oral route; generic symptoms (BUT 5% flaccid paralysis)

41
Q

State the structure and genotype of Orthomyxoviruses (and most significant example)

A

ssRNA, enveloped (influenza)

42
Q

Name two examples of antiflu drugs that block virus exit from cells

A

Tamiflu and Relenza

43
Q

State the structure and genome type of Herpesviridae Family (and name 3 subfamilies)

A

Icosahedral, Enveloped, dsDNA viruses (Alphaherpesviridae, Betaherpesviridae, Gammaherpesviridae)

44
Q

What is the common distinguishing feature of Alphaherpesviridae (and what molecule has been implicated in this feature)?

A

Latency and Reactivation (cortisol/stress)

45
Q

What drug can be used to treat HSV1/Herpes Simplex Virus 1 (and what stage of the viral life cycle does it inhibit)?

A

Acyclovir (ACV) - blocks viral DNA synthesis

46
Q

Name the structure + genome type of Paramyxoviruses (and two main examples)

A

Helical, Enveloped, ssRNA (Measles and Mumps)

47
Q

State structure + genome type of Togaviridae (and main example)

A

Enveloped, ssRNA (Rubella -> Congenital)

48
Q

State structure and genome type of Papovaviridae (Papilloma viruses), and main symptom

A

Icosahedral, dsDNA (cause warts which can be oncogenic)

49
Q

What family does Ebola belong to (and structure + genome type)?

A

Filoviridae (ssRNA)

50
Q

Name the three factors in the disease triangle

A

Pathogen/Susceptible Host/Favourable Environment for Pathogen

51
Q

Name the fungus that caused the potato blight in 1840s Ireland

A

Phytophthera infestans

52
Q

Name the 5 stages of causing disease in plants

A
  1. Pathogen must recognise the host
  2. Penetrate host barriers
  3. Suppress host defence systems
  4. Move (invade) through host tissues
  5. Utilise host components for growth and reproduction (nutrition)
53
Q

Name 3 virulence factors produced by plant pathogens

A

Enzymes (penetration, movement within host, breakdown of large molecules), Toxins (interfere with host cell functions in advance of pathogen), Growth Regulators

54
Q

Why can the influenza virus mutate so quickly?

A

It can undergo ANTIGENIC SHIFT when the RNA segments of two different strains undergo reassortment in the host

55
Q

What is the structure + genome type of Adenoviruses?

A

Icosahedral, dsDNA viruses (diameter 80nm)

56
Q

Full name, Structure + Genome of CTV?

A

Citrus Tristeza Virus -> +ssRNA; flexous rod, helical symmetry

57
Q

Name the vector that spreads CTV, and how it spreads in the plant

A

Brown citrus aphid, phloem

58
Q

Full name, structure + Genome of TMV

A

Tobacco mosaic virus; +ssRNA, helical

59
Q

Symptoms of CTV in plants?

A

Clear veins which turn corky, chlorosis followed by leaf cupping, die back

60
Q

Symptoms of TMV?

A

Chlorosis; Mosaic-like Mottling on Leaves; Rugosity -> stunted growth, lower yields

61
Q

Which virulence factors can cause soft rots in plants?

A

Enzymes such as Pectinases, proteases, cellulases (which degrade cell walls)

62
Q

Name the genus of bacteria which causes Crown Gall Tumours

A

Agrobacterium (tumifacens)

63
Q

How does Agrobacterium cause Crown Gall Tumours?

A

Enters the plant through wounds -> transfers its own DNA (T-DNA) into plant genome -> upregulates plant hormones auxin and cytokinin

64
Q

Name the bacterium which has been used as a biocontrol agent against insects (also its Gram ID and the toxin it produces)

A

Bacillus thuringiensis (Gram +ve rod) -> Bt toxin

65
Q

Why is the Bt toxin insect-specific?

A

It is highly insoluble in normal conditions - only soluble in high pH (alkaline) conditions of insect gut, where it forms pores in gut wall

66
Q

Name the fungal species which is known as Greenguard and used as a biocontrol agent

A

Metarhizium sp.

67
Q

Name two other fungal species besides Greenguard which are used as biopesticides

A

Entomophthorales (Zygomycetes) and Beuvaria bassiana (thrips, mealy bugs, weevils, white fly aphids)

68
Q

Name a species of Nematode-trapping fungi

A

Arthrobotrys

Microbes (7 decks)

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