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
2
Q
What may diseases be caused by?
A
Micro-organisms (microbes)
Multi-cellular organisms
3
Q
Examples of micro-organisms
A
Bacteria
Fungi
Protozoa
Viruses
4
Q
What are the characteristics of micro-organisms?
A
Non-pathogenic
Pathogenic
5
Q
What are the characteristics of non-pathogenic micro-organisms?
A
Not disease causing
Many are symbiotic
6
Q
What is the ratio of bacterial cells to human cells
A
10:1
7
Q
Examples of microbe relationships
A
Commensal
Mutualistic
Parasitic
Opportunistic
8
Q
What is a commensal microbial relationship?
A
Symbiotic relationship between organisms
One benefits; the other is unaffected
9
Q
Examples of commensal microbial relationships
A
Microbes on skin
Microbes in large intestine
10
Q
What is a mutualistic microbial relationship?
A
Symbiotic relationship between organisms
Both benefit
11
Q
Example of a mutualistic microbial relationship
A
E. coli make vit K for humans
12
Q
What is a parasitic microbial relationship?
A
Symbiotic relationship between organisms
One benefits but at the other’s expense
13
Q
Example of a parasitic microbial relationship
A
Head lice
14
Q
What is an opportunistic microbial relationship?
A
Symbiotic relationship between organisms
Initially commensal/mutualistic that becomes parasitic
15
Q
Example of an opportunistic microbial relationship
A
Candida
16
Q
What was Pasteur’s theory of microbes?
A
‘Germ theory of disease’
All germs are bad and cause disease
17
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
18
Q
How can microbes be identified and characterised?
A
Cultured in lab
Light microscope
Electron microscope
19
Q
Which microbes can be seen under a light microscope?
A
Whole micro-organisms
20
Q
Which microbes can be seen under an electron microscope?
A
Viruses
21
Q
What are the characteristics of bacteria?
A
Prokaryotic
No nucleus
No membrane-bound organelles
22
Q
What is the control centre of bacteria?
A
Single loop of DNA
23
Q
What two types of cell wall can bacteria have?
A
Gram positive
Gram negative
24
Q
What is a gram positive cell wall?
A
Thick
Mesh like
Made from peptidoglycan (proteins/carbs)
25
What is a gram negative cell wall?
Thin
| Additional outer lipid-rich membrane (fats/carbs)
26
What does the Gram staining method do?
Helps to understand category type of bacteria
27
What does the Gram staining method show?
Purple stain = gram positive
| Pink stain = gram negative
28
What shape is bacilli bacteria?
Rod-shaped
29
Example of bacilli bacteria
E. coli
30
What shape is cocci bacteria?
Spherical
31
Example of cocci bacteria
Streptococci
| Staphylococci
32
What shape is spirochetes bacteria?
Spiral-shaped
33
How do bacteria reproduce?
Binary fission
34
What is binary fission?
Enables bacteria to reproduce in high numbers at a rapid rate
35
What is spore formation?
Structure extremely resistant to hostile physical and chemical conditions e.g. heat and disinfections
36
What are invasive enzymes?
Enzymes produced by some bacteria to help them break down a host
37
What are the characteristics of exotoxins?
Gram positive and negative
Released by a living microbe
Very toxic
38
What are the characteristics of endotoxins?
Gram negative
Released after organism death from cell wall
Stimulates inflammatory cascade leading to fever, malaise
Usually less toxic
39
Examples of an exotoxin
Diphtheria
E. coli
C. tetani
40
Example of an endotoxin
Salmonella
41
Where can microflora be found?
```
Skin
Nasal cavity
Mouth
Small/large intestine
Vagina
Perineum
```
42
Where is microflora absent?
```
Blood
CSF
Lungs
Stomach
Bladder/kidneys
Uterus/fallopian tubes/ovaries
```
43
What can make organisms within microflora become pathogenic?
If local environment changes
| If immune system becomes compromised
44
What are antibiotics?
Conventional drugs that destroy bacteria
45
What are the two groups of antibiotics?
Broad spectrum
| Narrow spectrum
46
What do broad spectrum antibiotics target?
Target any bacteria (including body's healthy microflora)
47
What do narrow spectrum antibiotics target?
Only a small group of bacteria
48
What are the issues with antibiotics?
Often overprescribed
Adverse effects
Antibiotic resistance
49
What is higher antibiotic use linked to?
Higher risk of disease e.g. asthma, IBD
50
What don't antibiotics help with?
Viruses e.g. cold, flu, cold sores
51
What are some of the adverse effects associated with antibiotic use?
Impaired immunity
Candida overgrowth
Diarrhoea
52
What are viruses?
Intracellular parasites that need a living host for survival and replication
53
How is a virus structured?
Strand of DNA or RNA
Capsid (hard protein coat)
Envelope
Spikes (for attaching to specific cell surfaces)
54
What is special about the capsid?
It's unique for each virus
55
Which are the smallest microbes?
Viruses
56
How many virus microbes are said to fit on the head of a pin?
500 million
57
What are the two types of viruses?
DNA virus
| RNA virus
58
Examples of DNA viruses
Varicella zoster
Herpes zoster
Smallpox
59
Examples of RNA viruses
Measles
Mumps
HIV
60
How do viruses reproduce?
By injecting their DNA/RNA strand into a living host cell and using the host cell's apparatus for reproduction
61
Can viruses infect any host cells?
No, they infect specific host cells due to surface spike proteins
62
What happens when a virus binds with a cell?
It only allows entry of the genetic (DNA/RNA) material
| Capsid remains outside
63
What happens to the host cell once the virus leaves it?
It bursts (viral lysis)
64
Why are viruses hard for the body and anti-viral drugs to identify and destroy?
They hide inside host cells
They don't have a metabolism of their own
They don't have many structures of their own
They are able to mutate (change their surface antigens)
65
In what ways can viruses replicate?
Viral lysis
Viral budding
Latent stage
66
What happens during viral lysis?
Virus particles burst out of the host cell into the extracellular space, killing the host cell
67
What happens during viral budding?
Virus exits a cell by acquiring an envelope (outer membrane) of its own from the host cell membrane
Usually leads to host cell death
68
What happens during the latent stage?
Disease is present but hidden and inactive
| Can remain latent for years
69
What are fungi?
Eukaryotic organisms
70
What are the different ways fungi are structured?
Single-celled
| Complex multicellular organisms
71
What is found in the cell wall of fungi?
Melanin
72
Where can fungi be found?
Soil
Mouldy bread
Medicine
Food
73
What are filaments of fungi called?
Hyphae
74
What is a mass of fungi filaments called?
Mycelium
75
What are the characteristics of fungal infections?
Often opportunistic
| Occur in immune-compromised patients e.g. HIV, diabetes mellitus
76
What is a fungal infection also known as?
Mycosis
77
What are the three types of fungi that usually cause infection?
Yeasts
Moulds
Dermatophytes
78
What are yeasts?
Single-celled fungus
| Reproduces through budding
79
Example of a yeast
Candida albicans
80
What are moulds?
Multi-cellular fungi
Some cause disease
Some are involved in the production of foods/antibiotics
81
Examples of moulds
Aspergillus
| Penicillium
82
What are dermatophytes?
Fungi causing skin disease
83
How do dermatophytes exist?
They obtain nutrients from keratin in skin and colonise the stratum corneum
84
Examples of dermatophytes
Ringworm
| Tinea
85
What do fungi need to grow?
Warmth
Acidity
Rich nutrition
Moisture
86
How do fungi reproduce?
Asexual reproduction
| Sexual reproduction
87
How does asexual reproduction occur among fungi?
Via budding
| Hyphae extends containing chromatin and eventually detaches and develops into an independent organism
88
How does sexual reproduction occur among fungi?
By forming fungal spores
89
What are protozoa?
Single cell
| Eukaryotic organisms
90
What are the characteristics of protozoa?
Single-celled
No cell wall
Just a membrane
91
Where can you find protozoa?
Moist environments such as:
Fresh water
Soils
Ocean
92
How can protozoa move?
Flagella
Cilia
Vector
93
How do protozoa reproduce?
Binary fission
Budding
Sexual reproduction
Cysts
94
What are helminths?
Parasitic worms
95
What are the characteristics of helminths?
Eukaryotic
Macroscopic
Multi-cellular
96
What is the lifecycle of a helminth?
Egg
Larva
Adult
97
Where can helminths live?
Blood
Intestines
Tissue
98
Examples of helminths
Pinworm
Roundworm
Tapeworm
99
What are most helminths?
Intestinal parasites
100
Definition of 'infection'
Invasion of a host by a pathogen causing disease
101
What are the categories of where infections may occur?
Single individuals
Large groups
Worldwide
Restricted to an area
102
What is an infection in large groups called?
Epidemic
103
What is an infection worldwide called?
Pandemic
104
What is an infection restricted to an area called?
Endemic
105
What is a reservoir?
Location where the pathogen exists, reproduces and spreads to new hosts
106
What is a carrier?
Infected individuals who are asymptomatic
107
What is a vector?
Intermediate carrier, transporting pathogens from reservoir to host e.g. mosquito with malaria
108
What is a host?
Infected person or animal e.g. mosquito
109
How can infections be transmitted?
```
Droplets
Direct contact
Indirect contact
Vectors
Nosocomial
```
110
Examples of droplet transmission
Coughing with flu, COVID, scarlet fever
111
Examples of direct contact
Faeces
| Another individual
112
Examples of indirect contact
Food
Public transport
Toys
113
Examples of nosocomial
Hospital setting
| Care facility
114
How can infections be acquired?
```
Ingestion
Direct to blood stream e.g. injection, open wound
Sexual intercourse
Inhalation
Touch
Placental
```
115
What are the four stages of infection?
Incubation period
Prodromal period
Acute period
Chronic infection
116
What is the incubation period?
Time interval between initial exposure to the infecting organism and the appearance of the first signs or symptoms
117
What is the prodromal period?
Interval between non-specific symptoms (malaise, fever, fatigue) to more specific acute symptoms
118
What is the acute period?
Pathogen peaks in population
| Very pronounced symptoms specific to the disease
119
What is a chronic infection?
Infection with insidious or slow onset of long duration
120
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
```
121
How does a microbe infect a host?
```
Production of invasive enzymes
Production of endo- or exo- toxins
Spore formation
Forming colonies
Presence of bacterial capsule and pili
Mutation
```
122
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
```
123
What are the best forms of reducing the number of organisms?
Sterilisation
Disinfectants
Antiseptics
Pasteurisation
124
What is sterilisation and what does it do?
All micro-organisms and spores are destroyed
| Hot air: 30 mins at 180C
125
What does disinfectant do?
Destroys pathogenic microbes
| Not spores
126
What does antiseptic do?
Reduces number of organisms on the skin
| Not spores
127
What is pasteurisation and what does it do?
Kills most pathogenic microbes
Not spores
71.7C for 15-20 secs
128
What are natural forms of infection control?
```
Tea tree oil
Eucalyptus oil
Neem oil
Calendula
Colloidal silver
```
