Public: The microbiota of a few organ systems Flashcards

1
Q

What does the gastrointestinal tract consist of?

A

stomach, small intestine, and large intestine

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2
Q

What are the functions of the gastrointestinal tract?

A

digestion of food, absorption of nutrients, and production of nutrients by the indigenous microbial flora

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3
Q

How many microbial cells are in the GIT?

A

10^13 to 10^14 microbial cells

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4
Q

Where in the respiratory tract do microbial organisms colonise? Where are they less likely to colonise?

A

Upper respiratory tract

The lower respiratory tract lacks microflora in healthy individuals

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5
Q

Give examples of some microbiota in the upper respiratory tract

A

staphylococci, streptococci, diphtheroid bacilli, and gram-negative cocci and others

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6
Q

Name the organs in the upper respiratory tract

A

sinuses, nasopharynx, pharynx, oral cavity, larynx

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7
Q

Name the organs in the lower respiratory tract

A

trachea, bronchi, lungs

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8
Q

Altered pH can cause what to happen in the urogenital tract?

A

can cause potential pathogens in the urethra (such as Escherichia coli and Proteus mirabilis) to multiply and become pathogenic

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9
Q

Which organisms commonly cause urinary tract infections in women?

A

E. coli and P. mirabilis

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10
Q

What is the pH of the vagina like?

A

Slightly acidic (maintained by lactic acid), contains significant amounts of glycogen

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11
Q

Name a resident organism of the vagina. What does it do?

A

Lactobacillus acidophilus

Ferments the glycogen in the vagina, forming lactic acid to maintain the acid environment of the vagina

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12
Q

Define virulence

A

the relative ability of a pathogen to cause disease

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13
Q

How can virulence by measured?

A

Virulence can be estimated from experimental studies of the LD50 (lethal dose50)
= The amount of an agent that kills 50% of the animals in a test group
Highly virulent pathogens show little difference in the number of cells required to kill 100% of the population as compared to 50% of the population

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14
Q

Define attenuation

A

The decrease or loss of virulence

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15
Q

Define invasiveness

A

Ability of a pathogen to grow in host tissue at densities that inhibit host function
Can cause damage without producing a toxin

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16
Q

What is the causative agent of diphtheria?

A

Corynebacterium diphtheriae

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17
Q

Describe Corynebacterium diphtheria using the following points:

1) Gram positive/negative
2) Motile/non-motile
3) Morphology

A

1) Gram positive
2) Motile
3) Clubbed morphology

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18
Q

Clinical presentation of diphtheria

A

Pseudomembrane formation (in throat)
Difficulty swallowing
Systemic effects – heart complications, coma, death

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19
Q

Describe the pathogenesis of diphtheria

A

Inhalation of aerosols
Colonisation of throat
Produces single chained A-B toxin (DT)

Pseudomembrane formation in throat

AB toxin inhibits EF2 in eukaryotic cells
Inhibits protein synthesis

Death in 3 to 5% children

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20
Q

What is the causative agent of whooping cough? (pertussis)

A

Bordetella pertussis

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21
Q

Describe Bordetella pertussis using these points:

1) Gram positive/negative
2) Aerobic/anaerobic
3) humans/animals
4) Shape

A

1) Gram negative
2) Aerobic
3) Humans only
4) cocco-bacillus

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22
Q

Clinical presentation of whooping cough (pertussis)

A

Paroxysms of cough (whoop)
CNS effects
Secondary pneumonia

23
Q

Describe the pathogenesis of whooping cough (pertussis)

A

Attachment and replication on ciliated URT mucosa

Toxin production
Pertussis (exo)toxin
Tracheal cytotoxin (TCT)
Invasive adenylate cyclase toxin

Loss of mucociliary clearance
Violent coughing fits
Secondary pneumonia

24
Q

What are the 3 stages of pertussis disease progression?

A

Stage 1 - Catarrhal stage
Stage 2 - Paroxysmal stage
Stage 3 - Convalescent stage

25
Q

Describe the catarrhal stage of pertussis

A

May last 1-2 weeks
Symptoms: runny nose, low-grade fever, mild, occasional cough
Highly contagious

26
Q

Describe the paroxysmal stage of pertussis

A

Lasts 1-6 weeks, may last up to 12 weeks
Symptoms: fits of numerous, rapid cough characterised by “whoop” sound, vomiting and exhaustion after coughing fits (called paroxysmals)

27
Q

Describe the convalescent stage of pertussis

A

Lasts about 2-3 weeks
Susceptible to other respiratory infections for many
Recovery is gradual. Coughing lessens but fits of coughing may return.

28
Q

What is the causative agent of Cholera?

A

Vibrio cholera

29
Q

Wat is the shape of Vibrio cholera? Is it gram negative or gram positive?

A

comma shaped

gram negative

30
Q

Clinical presentation of severe cholera

A

Severe = rice water stools

31
Q

Pathogenesis of cholera

A

An acute infection of the GI tract (small intestine)

Production of cholera toxin

Adenylate cyclase upregulation

Massive fluid loss to GIT

Death through dehydration

Mortality
Up to 60% (untreated)
<1% electrolyte replacement

Short term carriage in up to 20% cases

Traveller vaccination?

32
Q

Name some non-invasive pathogens

A

Corynebacterium diphtheriae
Bordetella pertussis
Vibrio cholera

33
Q

Name some partially invasive pathogens

A

Shigella sonnei – mild infections
Shigella flexneri – severe infections
Shigella dysenteriae – very severe

34
Q

Possible causative agents of Shigellosis?

A

Shigella sonnei – mild infections
Shigella flexneri – severe infections
Shigella dysenteriae – very severe

35
Q

Describe Shigella organisms using the following questions:

1) Gram positive or negative?
2) Shape?
3) Aerobic/anaerobic
4) Spore forming/non spore forming?

A

1) Gram-negative
2) Rods
3) Facultative anaerobes
4) non spore forming

36
Q

Clinical presentation of shigellosis

A

Blood and puss in diarrhoea

37
Q

Pathogenesis of shigellosis

A

Attachment and invasion of distal ileum and colonic epithelia

Shiga toxin (an A-B toxin) 
Not excreted!! 

Partial invasion – no deeper than lamina propria

1.1 million deaths p.a.

38
Q

Name some primary invasive pathogens/diseses

A

typhoid (enteric fever)
rubella, chickenpox, measles - URT
polio, hepatitis -GIT

39
Q

Causative agent of enteric fever (typhoid)

A

Salmonella enterica serovar Typhi

Primary invasive pathogen

40
Q

Clinical presentation of typhoid (enteric fever)

A

Systemic infection
Constipation/diarrhoea
Fever
3 week symptom duration

3% become chronic carriers

41
Q

Transmission of enteric fever (typhoid)

A

No animal reservoir

Person to person spread or consumption of contaminated foods

No animal reservoir

Primary infection via jejunum or distal ileum (i.e. small intestine)

42
Q

pathogenesis of enteric fever (typhoid)

A

Bacteria induced uptake by M cells of epithelia
exocytosis of macrophage containing viable bacteria
systemic dissemination

43
Q

Give an example of a disease without bacterial colonisation

A

food poisoning

44
Q

true food poisoning (toxinoses) is

A

Consumption of food containing toxins (chemical or bacterial origin

45
Q

Causative agent of botulism

A

Clostridium botulinum

46
Q

Clostridium botulinum

1) Aerobic/anaerobic
2) spore forming/non spore forming
3) LD50
4) heat stable or not? How to inactivate the toxin?

A

1) obligately anaerobic
2) spore forming
3) Botulinum toxin (LD50 <0.01ng)
Highly potent neurotoxin
4)Heat stable
15 minutes boiling to inactivate

47
Q

Toxinoses of Staphylococcus aureus food poisoning

A

creamy foods, custards etc

48
Q

Cause of Staphylococcus aureus food poisoning

A

enterotoxins

49
Q

Symptoms of Staphylococcus aureus food poisoning

A

Rapid (1 – 6 h) symptoms- nausea, vomiting, abdominal pain, diarrhoea

50
Q

Bacillus cereus food poisoning

1) Aerobic/anaerobic?
2) spore forming/non spore forming?

A

1) obligately aerobic

2) spore forming

51
Q

What are the two disease forms of Bacillus cereus?

A

1) emetic toxin

2) enterotoxins Nhe and HBL

52
Q

Describe the emetic toxin disease form of Bacillus cereus

A

Heat stable

Short incubation

53
Q

Describe the enterotoxins (Nhe and HBL) of Bacillus cereus

A

Heat liable
Diarrhoea form
Longer incubation