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Theme 4 > Microorganisms and Infections > Flashcards

Microorganisms and Infections Flashcards

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1
Q

Mycoplasma -

Important feature and disease

A

Important feature: Lacks cell wall

Disease - Pneumonia

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2
Q

Virus - living cell or not ?

A

Not a living cell - cant replicate unless present in a living cell

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3
Q

List 2 types of Fungi with 3 points

A
  1. Candida albicans
    - A yeast
    - Unicellular
    - Reproduce by budding
  2. Aspergillus fumigatus
    - A mould
    - multicellular
    - Reproduce by spores
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4
Q

What is Plasmodium falciparium

A

Protozoa

is a malaria parasite

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5
Q

What are Helminths and give 2 examples

A

Eukaryotic cells like Protozoa and Fungi.

Example

  1. African eye worms
  2. beef Tape worm
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6
Q

What is taxonomy

A

Classification of organism

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7
Q

How are organisms named

A

Binomial nomenclature:-
Genus (like surname) first
Species (like given name) second
In italics or underlined

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8
Q

Are bacteria prokaryotes of Eukaryotes

A

Prokaryotes

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9
Q

List 5 differences between a Prokaryotic cell and a Eukaryotic cell

A

Prokaryotes vs Eukaryotes
No nucleus/membrane bound organelles vs membrane bound nucleus

Haploid vs Diploid

single circular DNA vs chromosome in nucleus

70S ribosome (30S and 50S subunits) vs 80S ribosome (40S and 60S subunits)

Peptidoglycan cell wall vs No cell wall (except plant and fungi)

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10
Q

Bacteria morphology

List 2 ways bacteria are classified

A
  1. by their Shape

2. Staining

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11
Q

List 5 bacteria morphology shapes

A
  1. Round - Coccus
  2. Long - Bacilli
  3. Branched - filamentous
  4. Spiral- spirillum/spirochete
  5. Comma- Vibro
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12
Q

Staining depends on

A

How much peptidoglycan is present in the cell wall

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13
Q

List the 5 stages of staining and the end results

A
  1. Fixation
  2. Crystal violet
  3. Iodine
  4. Ethanol (Decolorization)
  5. Safranin

If Pink = Gram negative
if Purple = Gram positive

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14
Q

Match the following

Clusters, Chain, Strepto-, Staphylo-

A 
Clusters = Staphylo-
Chains = Strepto-
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15
Q

3 types of bacteria based on atmosphere

A
  1. Anaerobes
  2. Anaerobes
  3. Facultative anaerobes- (can switch between aerobic and anaerobic metabolism)
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16
Q

List 3 bacterial growth requirements

A
  1. Temperature
  2. Salt content
  3. pH
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17
Q

Name 2 examples of Gram positive cocci bacteria

A
  1. Staphylococcus aureus

2. Streptococcus pyogenes

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18
Q

Name and example of Gram negative bacilli bacteria

A

Clostridium difficile

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19
Q

Name an example of Gram negative cocci bacteria

A

Neisseria meningitidis

Neisseria gonorrhoea

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20
Q

Name 3 examples of Gram negative bacilli

A

Enterobacteriacie

  • Salmonella & shigella
  • E. Coli
  • Klebsiella & Enterobacter
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21
Q

Name 2 bacteria without cell walls

A
  1. Mycoplasmas-Mycoplasma Pnuemoniae

2. Chlamydia- Chlamydia trachomatis

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22
Q

Name a bacteria that has a cell wall but does not stain well with Gram stains

A

Mycobacteria

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23
Q

List 3 structures present in Gram positive bacteria

A
  1. Thick peptidoglycan cell wall
  2. Teichoic acid
  3. Lipoteichoic acid
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24
Q

List 5 structures present in a Gram negative bacteria

A
  1. Lipopolysaccharide (on the outer membrane)
  2. Porin
  3. O specific chains
  4. Thin peptidoglycan wall (between the membranes)
  5. Integral proteins (between the bilayer)
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25
Q

What is the main job of lipopolysaccharide

A

Endotoxin

Endo means ‘part of’

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26
Q

List 3 features of a Peptidoglycan cell wall

A
  1. N-acetylated sugars
    - glucosamine(NAG) and muramic acid (NAM)
  2. 3-5 amino acid peptides
  3. Transpeptidase enzymes (involved in cell wall synthesis)
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27
Q

list 3 steps involved in the synthesis of peptidoglycan

A
  1. Polymerisation of sugar (NAM and NAG)
  2. Elongation of aa (add peptides)
  3. Cross link transpeptidase
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28
Q

Why cant Mycobacteria be stained and what other feature enables its survival

A

Its peptidoglycan is protected by an outer membrane called Myco-membrane/mycolic membrane. Prevents crystal violet from going into the bacteria. It also allows mycobacteria to be anti-phagocytic.

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29
Q

List 2 disease caused by Mycobacteria

A
  1. Tuberculosis

2. Leprosy

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30
Q

List 6 important features of bacteria

A
  1. Capsule
  2. Spores
  3. Ribosomes
  4. Peptidoglycan cell wall
  5. Lipopolysaccharides (in Gram negatives)
  6. Mobile genetic elements (Plasmids and transposons-move location in genome)
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31
Q

Plasmids and transposons are mobile genetic elements that codes for toxins and antibiotic resistance genes. True or False

A

True

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32
Q

Endo spores in some bacteria enables it to develop resistance to…
List 4 processes

A
  1. Drying
  2. Temperature
  3. Disinfection
  4. Digestion
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33
Q

List the 4 stages in bacterial growth

A
  1. The lag phase (bacteria adapting to new environment)
  2. The Exponential phase
  3. The Stationary phase (nutrients in cells become depleted, division stops)
  4. Death phase (exhaustion of resources)
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34
Q

List the 5/6 main mechanisms of viral pathogenesis

A 
1. Implantation at site of entry (normally sterile sites)
Survive after entry
2. Local replication
3. Spread to target organs
4. Multiplication at target organ
5. Shedding of virus into atmosphere
35
Q

Describe types of viral infections

A
  1. Acute infection

2. Chronic infection (Continuous replication + latency)

36
Q

What is Latency

A

Persistence of Viral DNA after infection. Can either be extrachromosomal element (herpesviruses) or integrated within the host genome (retroviruses) and is also replicated when cell replicates.
Reactivation(HV) as blisters, cold sores or shingles from chicken pox/Transformation(RS) of cell leading to cancer

37
Q

Explain methods of acquiring viral infection

A
  1. Endogenous - Latency Reactivation

2. Exogenous

38
Q

What is Virulence

A

Virulence is how likely an organism is to cause an infection or a disease. It is how likely how organism is a pathogen or a commensal

39
Q

What is Cell tropism

A

An organism has a predilection(liking) for particular cell types/tissues/organs

40
Q

What is susceptibility

A

A cell posses a surface molecule that acts as a virus receptor.
Which makes the cell susceptible to the virus

41
Q

What is permissivity

A

When a cell has appropriate transcription factors/enzyme pathways that allows it to switch on viral genes to produce viral proteins.

The cell is permissive to the production of viral proteins

42
Q

List different methods of viral diagnosis

A
  1. Microscopy
  2. Culture
  3. Detection of antibody mounted against the virus
  4. Detection of viral protein
  5. Detection of viral nuclei acid (Using PCR- Polymerase Chain Reaction)
43
Q

Explain concepts of viral prevention and treatment

A

Prevention - General measures such as masks, gloves + Specific measures such as vaccines

Treatment - Antiviral medicines

44
Q

What is a virion + Nucleocapsid

A

Virion = Complete virus particle

Nucleocapsid = Nuclei acid + protein coat (like a capsule)

45
Q

What immune system controls Latent viruses

A

Immuno-surveillance

46
Q

List 2 factors that can increase the likelihood of virus reactivation

A
  1. Aging

2. Immunosuppression

47
Q

What is a commensalisation ?

A

An association between two organisms in which one benefits and the other derives neither benefit or harm.

A commensal is an organism that lives on us but does not cause an infection.

E.g normal microbial flora

48
Q

What is symbiosis

A

It involves mutual benefit. E.g a mitochondria, takes in nutrients, but produces/releases energy

49
Q

What is a pathogen

A

An organism which can evade the immune defences of human to cause and infection.

50
Q

What is infection

A

When an organism gains entry to the body, increase in number and damages its host (invasion, replication and damage)

51
Q

List 3 examples of non-sterile site

A

Skin,
Mucosal surfaces of upper respiratory tract, alimentary canal
Female genital tract

52
Q

List 3 examples of sterile site

A

Blood, C.S.F, Bone & joints, muscle, sub-cutaneous tissue, Urine -bladder or renal tract

53
Q

List 2 routes of organisms transmission in the body

A
  1. Through the lymphatics

2. Through the blood

54
Q

List 2 reasons why some people get infected and others do not

A
  1. Increased genetic susceptibility, e.g presences of SCD gene in malaria, CFTR gene for C.F (apparently shows resilient to cholera)
  2. Inadequate immune response (immunocompromised)
55
Q

Why do some people get sicker than others after an infection

A
  1. Inappropriate or excessive immune response e.g septic shock
56
Q

List 2 ways people can become immunocompromised

A
  1. Primary immunodeficiency syndromes - from birth

2. Acquired immunodeficiency- from disease e.g AIDS

57
Q

What is a professional pathogen

A

A pathogen that almost always causes disease

58
Q

What is an opportunistic pathogen

A

A pathogen that only causes disease in immunocompromised patient

59
Q

List 3 examples of an opportunistic pathogen

A
  1. Candida albicans
  2. staphylococcus epidermidis
  3. Staphylococcus aureus
60
Q

List 3 examples of a professional pathogen

A
  1. Neisseria meningitidis
  2. Malaria
  3. HIV
61
Q

Is staphylococcus aureus a commensal ?

A

Yes

Lives in the anterior nares

62
Q

Function of Adhesin molecules in S. aureus virulence

A

Adhesin molecules -

  1. allows it to bind to collagen/elastin on host proteins
  2. Immune evasion- as immune system think they are part of the tissue they are bounded to
63
Q

Function of Protein A in S. aureus virulence

A

Binds to the Fc region of igG antibody. Prevent the Fab region from binding to it.

64
Q

Function of Coagulase in S. aureus virulence

A

Coagulase on S. aureus stimulates blood clotting. This reduces locomotion of immune cells. Aiding S. aureus in immune evasion.

65
Q

Function of Toxins in S. aureus virulence

A

Lyse host cells
Exfoliative toxins contain protease that breaks down epidermal structural proteins
Enterotoxins - causes vomiting

66
Q

Function of Capsule in S. aureus virulence

A

Prevents opsonisation by
1. Preventing FAb region from binding onto the peptidoglycan
2. Even if it does, it prevents Antibody and Complement receptor from binding to their respective antibody/complement.
Hence preventing opsoniosation

67
Q

List 5 features of S. aureus that enables its virulence

A
  1. Adhesins molecule
  2. Protein A
  3. Coagulase
  4. Toxins
  5. Capsule
68
Q

Name 2 skin infections caused by S. Aureus

A
  1. Impetigo

2. Staph abscess

69
Q

Name a vascular line infection caused by S. aureus

A

S aureus line sepsis

70
Q

S. aureus causes vomiting as a result of food poisoning with enterotoxins. True or False

A

True

71
Q

LPS interaction with TLR-4 on macrophage/endothelium causes

A

Sepsis

  1. Inflammatory pathways
  2. Coagulation and clotting pathways
  3. Change in endothelial integrity
72
Q

TLR 4 recognises LPS

TLR 2- recognises Lipoteichoic acid/peptidoglycan. True or False

A

True

73
Q

Non-blanching means

A

When pressed with glass, the spots remain red

74
Q

List 2 features of Clostridium difficile that aids pathogenicity/virulence

A
  1. Makes toxins that causes diarrhoea

2. Production of spores (remember they are rod shaped)

75
Q

Bacteria that can make ATP with or without oxygen are called

A

Facultative Anaerobe

76
Q

Endotoxin is a feature of the Gram _______ cell wall

A

Gram Negative cell wall

77
Q

List 2 advantages of Culture-based diagnosis

A
  1. Good for detecting bacteria you can grow/stain

2. Reliable identification and resistance testing

78
Q

List 2 disadvantage of culture-based diagnosis

A
  1. Very slow

2. Labour intensive

79
Q

Main method used in Microscopy for diagnosis is

A

Gram staining

80
Q

What is Serology?

A

Use of serum (blood) to test for immune count. E.g Antibody count

81
Q

Disadvantage of serology

A

Might need two test. Antibodies can take time to develop (weeks)

82
Q

2 Disadvantage of PCR

A

Can pick up latent infection in DNA

Has a poor positive predictive value

83
Q

Advantages of PCR

A

Good negative predictive value

84
Q

2 Advantages of Whole genome sequencing

A
  1. Rapid

2. Cheap

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