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BioMed S2 > 16. Infectious Diseases > Flashcards

16. Infectious Diseases Flashcards

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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
What does the Gram staining method do?
Helps to understand category type of bacteria
26
What does the Gram staining method show?
Purple stain = gram positive Pink stain = gram negative | After washing in ethanol
27
What shape is bacilli bacteria?
Rod-shaped
28
Example of bacilli bacteria
E. coli
29
What shape is cocci bacteria?
Spherical
30
Example of cocci bacteria
Streptococci Staphylococci
31
What shape is spirochetes bacteria?
Spiral-shaped
32
How do bacteria reproduce?
Binary fission
33
What is binary fission?
Asexual, simple mitosis Enables bacteria to reproduce in high numbers at a rapid rate (exponentially) | eg E coli reproduces in 20mins
34
What is a spore formation?
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
35
What are invasive enzymes?
Enzymes produced by some bacteria to help them break down a host | eg in Scarlet Fever enzymes produced by haemolytic streptococci
36
What are the characteristics of exotoxins?
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
37
What are the characteristics of endotoxins?
Only Gram negative Released after organism death from cell wall (LPS molecules) Stimulates inflammatory cascade leading to fever, malaise Usually less toxic | eg Salmonella
38
Examples of an exotoxin
Diphtheria E. coli C. tetani
39
Example of an endotoxin
Salmonella
40
Where can microflora be found?
Skin Nasal cavity Mouth Small/large intestine Vagina Perineum
41
Where is microflora absent? | i.e should be sterile
Blood CSF Lungs Stomach Bladder/kidneys Uterus/fallopian tubes/ovaries | if even commensal bacteria enters it can cause disease eg cystitis
42
What can make organisms within microflora become pathogenic?
If local environment changes If immune system becomes compromised
43
What are antibiotics?
Conventional drugs that destroy bacteria
44
What are the two groups of antibiotics?
Broad spectrum* Narrow spectrum | Commonly used to avoid cost of detecting the specific bacteria
45
What do broad spectrum antibiotics target?
Target any bacteria (including body's healthy microflora)
46
What do narrow spectrum antibiotics target?
Only a small group of bacteria
47
What are the issues with antibiotics?
Often overprescribed Adverse effects Antibiotic resistance
48
What is higher antibiotic use linked to?
Higher risk of disease e.g. asthma, IBD
49
What don't antibiotics help with?
Viruses e.g. cold, flu, cold sores
50
What are some of the adverse effects associated with antibiotic use?
Impaired immunity Candida overgrowth Diarrhoea
51
What are viruses?
Intracellular parasites that need a living host for survival and replication
52
How is a virus structured?
Strand of DNA or RNA Capsid (hard protein coat) Envelope Spikes (for attaching to specific cell surfaces)
53
What is special about the capsid?
It's unique for each virus
54
Which are the smallest microbes?
Viruses
55
How many virus microbes are said to fit on the head of a pin?
500 million
56
What are the two types of viruses?
DNA virus RNA virus
57
Examples of DNA viruses
Varicella zoster* Herpes zoster Smallpox | *chickenpox/shingles
58
Examples of RNA viruses
Measles Mumps HIV
59
How do viruses reproduce?
By injecting their DNA/RNA strand into a living host cell Using the host cell's apparatus for reproduction
60
Can viruses infect any host cells?
No, they infect specific host cells due to surface spike proteins
61
What happens when a virus binds with a cell?
It only allows entry of the genetic (DNA/RNA) material Capsid remains outside
62
What happens to the host cell once the virus leaves it?
It bursts (viral lysis)
63
Why are viruses hard for the body and anti-viral drugs to identify and destroy?
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
In what ways can viruses replicate?
Viral lysis Viral budding Latent stage
65
What happens during viral lysis?
Virus particles burst out of the host cell into the extracellular space, killing the host cell
66
What happens during viral budding?
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
What happens during the latent stage?
Disease is present but hidden and inactive Can remain latent for years
68
What are fungi?
Eukaryotic organisms* | Have a nucleus
69
What are the different ways fungi are structured?
Single-celled or Complex multicellular organisms With cell walls
70
What is found in the cell wall of fungi?
Melanin
71
Where can fungi be found?
EVERYWHERE! Soil Mouldy bread Medicine Food
72
What are filaments of fungi called?
Hyphae
73
What is a mass of fungi filaments called?
Mycelium
74
What are the characteristics of fungal infections?
Often opportunistic Occur in immune-compromised patients e.g. HIV, diabetes mellitus Usually kept in check by CD4 T helper cells
75
What is a fungal infection also known as?
Mycosis
76
What are the three types of fungi that usually cause infection?
Yeasts Moulds Dermatophytes
77
What are yeasts?
Single-celled fungus Reproduces through budding
78
Example of a yeast
Candida albicans
79
What are moulds?
Multi-cellular fungi Some cause disease Some are involved in the production of foods/antibiotics
80
Examples of moulds
Aspergillus (causes lung disease) Penicillium (antibiotic)
81
What are dermatophytes?
Fungi causing skin disease
82
How do dermatophytes exist?
They obtain nutrients from keratin in skin and colonise the stratum corneum
83
Examples of dermatophytes
Ringworm Tinea (head/foot)
84
What do fungi need to grow?
Warmth Acidity Rich nutrition Moisture
85
How do fungi reproduce?
Asexual reproduction Sexual reproduction
86
How does asexual reproduction occur among fungi?
Via budding Hyphae extends containing chromatin and eventually detaches and develops into an independent organism
87
How does sexual reproduction occur among fungi?
By forming fungal spores
88
What are protozoa?
Single cell Eukaryotic organisms | eg Plasmodium (malaria)
89
What are the characteristics of protozoa?
Single-celled No cell wall Just a membrane
90
Where can you find protozoa?
Moist environments such as: Fresh water Soils Ocean
91
How can protozoa move?
Flagella Cilia Vector* | *intermediate carrier eg mosquito in maleria
92
How do protozoa reproduce?
Binary fission Budding Sexual reproduction* Cysts | *only in unfavourable conditions
93
What are helminths?
Parasitic worms
94
What are the characteristics of helminths?
Eukaryotic Macroscopic Multi-cellular
95
What is the lifecycle of a helminth?
Egg Larva Adult
96
Where can helminths live?
Blood Intestines Tissue
97
Examples of helminths
Pinworm Roundworm Tapeworm
98
What are most helminths?
Intestinal parasites
99
Definition of 'infection'
Invasion of a host by a pathogen-causing disease
100
What are the categories of where infections may occur?
Single individuals Large groups Worldwide Restricted to an area
101
What is an infection in large groups called?
Epidemic
102
What is an infection worldwide called?
Pandemic
103
What is an infection restricted to an area called?
Endemic
104
What is a reservoir?
Location where the pathogen exists, reproduces and spreads to new hosts
105
What is a carrier?
Infected individuals who are asymptomatic
106
What is a vector?
Intermediate carrier, transporting pathogens from reservoir to host e.g. mosquito with malaria
107
What is a host?
Infected person or animal e.g. mosquito
108
How can infections be transmitted?
Droplets Direct contact Indirect contact Vectors Nosocomia
109
Examples of droplet transmission
Coughing with flu, COVID, scarlet fever
110
Examples of direct contact
Faeces Another individual
111
Examples of indirect contact
Food Public transport Toys
112
Examples of nosocomial
Hospital setting Care facility eg UTI, ulcers, pneumonia, surgical site infections
113
How can infections be acquired?
Ingestion Direct to blood stream e.g. injection, open wound Sexual intercourse Inhalation Touch Placental
114
What are the four stages of infection?
1. Incubation period 2. Prodromal period 3. Acute period 4. Chronic infection
115
What is the incubation period?
Time interval between initial exposure to the infecting organism and the appearance of the first signs or symptoms
116
What is the prodromal period?
Interval between non-specific symptoms (malaise, fever, fatigue) to more specific acute symptoms
117
What is the acute period?
Pathogen peaks in population Very pronounced symptoms specific to the disease
118
What is a chronic infection?
Infection with insidious or slow onset of long duration
119
How does a host resist an infection?
Intact skin and mucous membranes Body secretions - stomach acid, tears, saliva Phagocytosis Interferon production Effective inflammatory response Effective immune system
120
How does a microbe infect a host?
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
What ways can be used to control infection?
Reduce the reservoir Stop droplet transmission - cover mouth Block the method of transmission - wash hands, gloves Kill the organism Sterilisation
122
What are the best forms of reducing the number of organisms?
Sterilisation Disinfectants Antiseptics Pasteurisation
123
What is sterilisation and what does it do?
All micro-organisms and spores are destroyed Hot air: 30 mins at 180C Steam: 20 mins at 120C* | *Autoclaving
124
What does disinfectant do?
Chemicals that destroy pathogenic microbes Not spores
125
What does antiseptic do?
Reduces number of organisms on the skin Not spores | eg alcohol
126
What is pasteurisation and what does it do?
Kills most pathogenic microbes Not spores 71.7C for 15-25 secs
127
What are natural forms of infection control?
Tea tree oil Eucalyptus oil Neem oil Calendula Colloidal silver
128
What diseases are transmitted via protozoa ?
Malaria Dysentry
129
What is a protozoa ?
Single-celled organism

BioMed S2 (34 decks)

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