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BioMed S2 > 16. Infectious Diseases > Flashcards

16. Infectious Diseases Flashcards

1
Q

In what ways can an infectious disease be transmitted?

A

Human to human
Animal to human
Direct contact
Indirect contact

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2
Q

What may diseases be caused by?

A

Micro-organisms (microbes)
Multi-cellular organisms

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3
Q

Examples of micro-organisms

A

Bacteria
Fungi
Protozoa
Viruses

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4
Q

What are the characteristics of non-pathogenic micro-organisms?

A

Not disease causing
Many are symbiotic/commensal
Can become pathogenic

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5
Q

What is the ratio of bacterial cells to human cells ?

A

10:1

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6
Q

Examples of microbe relationships

A

Commensal
Mutualistic
Parasitic
Opportunistic

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7
Q

What is a commensal microbial relationship?

A

Symbiotic relationship between organisms
One benefits; the other is unaffected

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8
Q

Examples of commensal microbial relationships

A

Microbes on skin
Microbes in large intestine

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9
Q

What is a mutualistic microbial relationship?

A

Symbiotic relationship between organisms
Both benefit

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10
Q

Example of a mutualistic microbial relationship

A

E. coli make vit K for humans

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11
Q

What is a parasitic microbial relationship?

A

Symbiotic relationship between organisms
One benefits but at the other’s expense

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12
Q

Example of a parasitic microbial relationship

A

Head lice

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13
Q

What is an opportunistic microbial relationship?

A

Symbiotic relationship between organisms
Initially commensal/mutualistic that becomes parasitic (pathogenic)

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14
Q

Example of an opportunistic microbial relationship

A

Candida
Flourishes when environment is suitable

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15
Q

What was Pasteur’s theory of microbes?

A

‘Germ theory of disease’
All germs are bad and cause disease

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16
Q

What was Bechamp’s theory of microbes?

A

Germs are opportunistic in nature and live with us symbiotically
Terrain theory - the terrain provides the environment for bacteria to grow
Promote health through diet and exercise to promote healthy bacteria

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17
Q

How can microbes be identified and characterised?

A

Cultured in lab
Light microscope
Electron microscope

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18
Q

Which microbes can be seen under a light microscope?

A

Whole micro-organisms
Bacteria/fungus

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19
Q

Which microbes can be seen under an electron microscope?

A

Viruses

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20
Q

What are the characteristics of bacteria?

A

Prokaryotic
No nucleus
No membrane-bound organelles

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21
Q

What is the control centre of bacteria?

A

Single loop of DNA

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22
Q

What two types of cell wall can bacteria have?

A

Gram positive
Gram negative

From Gram staining

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23
Q

What is a gram positive cell wall?

A

Thick cell wall
Mesh like
Made from peptidoglycan (proteins/carbs)
Purple stain

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24
Q

What is a gram negative cell wall?

A

Thin cell wall
Additional outer lipid-rich membrane (fats/carbs)*
Pink stain

*lipopolysacchrides (LPS) which cause effets on death of bacteria

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25
Q

What does the Gram staining method do?

A

Helps to understand category type of bacteria

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26
Q

What does the Gram staining method show?

A

Purple stain = gram positive
Pink stain = gram negative

After washing in ethanol

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27
Q

What shape is bacilli bacteria?

A

Rod-shaped

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28
Q

Example of bacilli bacteria

A

E. coli

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29
Q

What shape is cocci bacteria?

A

Spherical

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30
Q

Example of cocci bacteria

A

Streptococci
Staphylococci

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31
Q

What shape is spirochetes bacteria?

A

Spiral-shaped

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32
Q

How do bacteria reproduce?

A

Binary fission

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33
Q

What is binary fission?

A

Asexual, simple mitosis
Enables bacteria to reproduce in high numbers at a rapid rate (exponentially)

eg E coli reproduces in 20mins

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34
Q

What is a spore formation?

A

Structure extremely resistant to hostile physical and chemical conditions e.g. heat and disinfections
Spores are dormant (hide when environment is harsh)
Part of the life cycle of bacteria, fungi and protozoans

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35
Q

What are invasive enzymes?

A

Enzymes produced by some bacteria to help them break down a host

eg in Scarlet Fever enzymes produced by haemolytic streptococci

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36
Q

What are the characteristics of exotoxins?

A

Gram positive and negative bacteria
Released by a living microbe (eg E coli)
Very toxic
Protein toxins (eg botox)

eg diptheria bind to pharynx cells and inhibit protein sythesis

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37
Q

What are the characteristics of endotoxins?

A

Only Gram negative
Released after organism death from cell wall (LPS molecules)
Stimulates inflammatory cascade leading to fever, malaise
Usually less toxic

eg Salmonella

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38
Q

Examples of an exotoxin

A

Diphtheria
E. coli
C. tetani

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39
Q

Example of an endotoxin

A

Salmonella

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40
Q

Where can microflora be found?

A

Skin
Nasal cavity
Mouth
Small/large intestine
Vagina
Perineum

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41
Q

Where is microflora absent?

i.e should be sterile

A

Blood
CSF
Lungs
Stomach
Bladder/kidneys
Uterus/fallopian tubes/ovaries

if even commensal bacteria enters it can cause disease eg cystitis

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42
Q

What can make organisms within microflora become pathogenic?

A

If local environment changes
If immune system becomes compromised

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43
Q

What are antibiotics?

A

Conventional drugs that destroy bacteria

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44
Q

What are the two groups of antibiotics?

A

Broad spectrum*
Narrow spectrum

Commonly used to avoid cost of detecting the specific bacteria

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45
Q

What do broad spectrum antibiotics target?

A

Target any bacteria (including body’s healthy microflora)

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46
Q

What do narrow spectrum antibiotics target?

A

Only a small group of bacteria

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47
Q

What are the issues with antibiotics?

A

Often overprescribed
Adverse effects
Antibiotic resistance

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48
Q

What is higher antibiotic use linked to?

A

Higher risk of disease e.g. asthma, IBD

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49
Q

What don’t antibiotics help with?

A

Viruses e.g. cold, flu, cold sores

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50
Q

What are some of the adverse effects associated with antibiotic use?

A

Impaired immunity
Candida overgrowth
Diarrhoea

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51
Q

What are viruses?

A

Intracellular parasites that need a living host for survival and replication

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52
Q

How is a virus structured?

A

Strand of DNA or RNA
Capsid (hard protein coat)
Envelope
Spikes (for attaching to specific cell surfaces)

53
Q

What is special about the capsid?

A

It’s unique for each virus

54
Q

Which are the smallest microbes?

55
Q

How many virus microbes are said to fit on the head of a pin?

A

500 million

56
Q

What are the two types of viruses?

A

DNA virus
RNA virus

57
Q

Examples of DNA viruses

A

Varicella zoster*
Herpes zoster
Smallpox

*chickenpox/shingles

58
Q

Examples of RNA viruses

A

Measles
Mumps
HIV

59
Q

How do viruses reproduce?

A

By injecting their DNA/RNA strand into a living host cell
Using the host cell’s apparatus for reproduction

60
Q

Can viruses infect any host cells?

A

No, they infect specific host cells due to surface spike proteins

61
Q

What happens when a virus binds with a cell?

A

It only allows entry of the genetic (DNA/RNA) material
Capsid remains outside

62
Q

What happens to the host cell once the virus leaves it?

A

It bursts (viral lysis)

63
Q

Why are viruses hard for the body and anti-viral drugs to identify and destroy?

A
  1. They hide inside host cells*
  2. They don’t have a metabolism of their own
  3. They don’t have many structures of their own
  4. They are able to mutate (change their surface antigens)

*can be latent for years/decades

64
Q

In what ways can viruses replicate?

A

Viral lysis
Viral budding
Latent stage

65
Q

What happens during viral lysis?

A

Virus particles burst out of the host cell into the extracellular space, killing the host cell

66
Q

What happens during viral budding?

A

Virus exits a cell by acquiring an envelope (outer membrane) of its own from the host cell membrane
Protects from body’s immune system
Usually leads to host cell death

eg HIV

67
Q

What happens during the latent stage?

A

Disease is present but hidden and inactive
Can remain latent for years

68
Q

What are fungi?

A

Eukaryotic organisms*

Have a nucleus

69
Q

What are the different ways fungi are structured?

A

Single-celled or
Complex multicellular organisms
With cell walls

70
Q

What is found in the cell wall of fungi?

71
Q

Where can fungi be found?

A

EVERYWHERE!
Soil
Mouldy bread
Medicine
Food

72
Q

What are filaments of fungi called?

73
Q

What is a mass of fungi filaments called?

74
Q

What are the characteristics of fungal infections?

A

Often opportunistic
Occur in immune-compromised patients e.g. HIV, diabetes mellitus
Usually kept in check by CD4 T helper cells

75
Q

What is a fungal infection also known as?

76
Q

What are the three types of fungi that usually cause infection?

A

Yeasts
Moulds
Dermatophytes

77
Q

What are yeasts?

A

Single-celled fungus
Reproduces through budding

78
Q

Example of a yeast

A

Candida albicans

79
Q

What are moulds?

A

Multi-cellular fungi
Some cause disease
Some are involved in the production of foods/antibiotics

80
Q

Examples of moulds

A

Aspergillus (causes lung disease)
Penicillium (antibiotic)

81
Q

What are dermatophytes?

A

Fungi causing skin disease

82
Q

How do dermatophytes exist?

A

They obtain nutrients from keratin in skin and colonise the stratum corneum

83
Q

Examples of dermatophytes

A

Ringworm
Tinea (head/foot)

84
Q

What do fungi need to grow?

A

Warmth
Acidity
Rich nutrition
Moisture

85
Q

How do fungi reproduce?

A

Asexual reproduction
Sexual reproduction

86
Q

How does asexual reproduction occur among fungi?

A

Via budding
Hyphae extends containing chromatin and eventually detaches and develops into an independent organism

87
Q

How does sexual reproduction occur among fungi?

A

By forming fungal spores

88
Q

What are protozoa?

A

Single cell
Eukaryotic organisms

eg Plasmodium (malaria)

89
Q

What are the characteristics of protozoa?

A

Single-celled
No cell wall
Just a membrane

90
Q

Where can you find protozoa?

A

Moist environments such as:
Fresh water
Soils
Ocean

91
Q

How can protozoa move?

A

Flagella
Cilia
Vector*

*intermediate carrier eg mosquito in maleria

92
Q

How do protozoa reproduce?

A

Binary fission
Budding
Sexual reproduction*
Cysts

*only in unfavourable conditions

93
Q

What are helminths?

A

Parasitic worms

94
Q

What are the characteristics of helminths?

A

Eukaryotic
Macroscopic
Multi-cellular

95
Q

What is the lifecycle of a helminth?

A

Egg
Larva
Adult

96
Q

Where can helminths live?

A

Blood
Intestines
Tissue

97
Q

Examples of helminths

A

Pinworm
Roundworm
Tapeworm

98
Q

What are most helminths?

A

Intestinal parasites

99
Q

Definition of ‘infection’

A

Invasion of a host by a pathogen-causing disease

100
Q

What are the categories of where infections may occur?

A

Single individuals
Large groups
Worldwide
Restricted to an area

101
Q

What is an infection in large groups called?

102
Q

What is an infection worldwide called?

103
Q

What is an infection restricted to an area called?

104
Q

What is a reservoir?

A

Location where the pathogen exists, reproduces and spreads to new hosts

105
Q

What is a carrier?

A

Infected individuals who are asymptomatic

106
Q

What is a vector?

A

Intermediate carrier, transporting pathogens from reservoir to host e.g. mosquito with malaria

107
Q

What is a host?

A

Infected person or animal e.g. mosquito

108
Q

How can infections be transmitted?

A

Droplets
Direct contact
Indirect contact
Vectors
Nosocomia

109
Q

Examples of droplet transmission

A

Coughing with flu, COVID, scarlet fever

110
Q

Examples of direct contact

A

Faeces
Another individual

111
Q

Examples of indirect contact

A

Food
Public transport
Toys

112
Q

Examples of nosocomial

A

Hospital setting
Care facility
eg UTI, ulcers, pneumonia, surgical site infections

113
Q

How can infections be acquired?

A

Ingestion
Direct to blood stream e.g. injection, open wound
Sexual intercourse
Inhalation
Touch
Placental

114
Q

What are the four stages of infection?

A
  1. Incubation period
  2. Prodromal period
  3. Acute period
  4. Chronic infection
115
Q

What is the incubation period?

A

Time interval between initial exposure to the infecting organism and the appearance of the first signs or symptoms

116
Q

What is the prodromal period?

A

Interval between non-specific symptoms (malaise, fever, fatigue) to more specific acute symptoms

117
Q

What is the acute period?

A

Pathogen peaks in population
Very pronounced symptoms specific to the disease

118
Q

What is a chronic infection?

A

Infection with insidious or slow onset of long duration

119
Q

How does a host resist an infection?

A

Intact skin and mucous membranes
Body secretions - stomach acid, tears, saliva
Phagocytosis
Interferon production
Effective inflammatory response
Effective immune system

120
Q

How does a microbe infect a host?

A

Production of invasive enzymes
Production of endo- or exo- toxins
Spore formation
Forming colonies (CFU)
Presence of bacterial capsule and pili
Mutation

CFU - colony forming units

121
Q

What ways can be used to control infection?

A

Reduce the reservoir
Stop droplet transmission - cover mouth
Block the method of transmission - wash hands, gloves
Kill the organism
Sterilisation

122
Q

What are the best forms of reducing the number of organisms?

A

Sterilisation
Disinfectants
Antiseptics
Pasteurisation

123
Q

What is sterilisation and what does it do?

A

All micro-organisms and spores are destroyed
Hot air: 30 mins at 180C
Steam: 20 mins at 120C*

*Autoclaving

124
Q

What does disinfectant do?

A

Chemicals that destroy pathogenic microbes
Not spores

125
Q

What does antiseptic do?

A

Reduces number of organisms on the skin
Not spores

eg alcohol

126
Q

What is pasteurisation and what does it do?

A

Kills most pathogenic microbes
Not spores
71.7C for 15-25 secs

127
Q

What are natural forms of infection control?

A

Tea tree oil
Eucalyptus oil
Neem oil
Calendula
Colloidal silver

128
Q

What diseases are transmitted via protozoa ?

A

Malaria
Dysentry

129
Q

What is a protozoa ?

A

Single-celled organism

BioMed S2 (34 decks)

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