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Flashcards in Public: The microbiota of a few organ systems Deck (53):
1

What does the gastrointestinal tract consist of?

stomach, small intestine, and large intestine

2

What are the functions of the gastrointestinal tract?

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

3

How many microbial cells are in the GIT?

10^13 to 10^14 microbial cells

4

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

Upper respiratory tract

The lower respiratory tract lacks microflora in healthy individuals

5

Give examples of some microbiota in the upper respiratory tract

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

6

Name the organs in the upper respiratory tract

sinuses, nasopharynx, pharynx, oral cavity, larynx

7

Name the organs in the lower respiratory tract

trachea, bronchi, lungs

8

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

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

9

Which organisms commonly cause urinary tract infections in women?

E. coli and P. mirabilis

10

What is the pH of the vagina like?

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

11

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

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

12

Define virulence

the relative ability of a pathogen to cause disease

13

How can virulence by measured?

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

14

Define attenuation

The decrease or loss of virulence

15

Define invasiveness

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

16

What is the causative agent of diphtheria?

Corynebacterium diphtheriae

17

Describe Corynebacterium diphtheria using the following points:
1) Gram positive/negative
2)Motile/non-motile
3)Morphology

1) Gram positive
2) Motile
3) Clubbed morphology

18

Clinical presentation of diphtheria

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

19

Describe the pathogenesis of diphtheria

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

20

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

Bordetella pertussis

21

Describe Bordetella pertussis using these points:
1) Gram positive/negative
2)Aerobic/anaerobic
3)humans/animals
4) Shape

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

22

Clinical presentation of whooping cough (pertussis)

Paroxysms of cough (whoop)
CNS effects
Secondary pneumonia

23

Describe the pathogenesis of whooping cough (pertussis)

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

What are the 3 stages of pertussis disease progression?

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

25

Describe the catarrhal stage of pertussis

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

26

Describe the paroxysmal stage of pertussis

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

Describe the convalescent stage of pertussis

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

28

What is the causative agent of Cholera?

Vibrio cholera

29

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

comma shaped
gram negative

30

Clinical presentation of severe cholera

Severe = rice water stools

31

Pathogenesis of cholera

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

Name some non-invasive pathogens

Corynebacterium diphtheriae
Bordetella pertussis
Vibrio cholera

33

Name some partially invasive pathogens

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

34

Possible causative agents of Shigellosis?

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

35

Describe Shigella organisms using the following questions:
1) Gram positive or negative?
2) Shape?
3) Aerobic/anaerobic
4) Spore forming/non spore forming?

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

36

Clinical presentation of shigellosis

Blood and puss in diarrhoea

37

Pathogenesis of shigellosis

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

Name some primary invasive pathogens/diseses

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

39

Causative agent of enteric fever (typhoid)

Salmonella enterica serovar Typhi
Primary invasive pathogen

40

Clinical presentation of typhoid (enteric fever)

Systemic infection
Constipation/diarrhoea
Fever
3 week symptom duration

3% become chronic carriers

41

Transmission of enteric fever (typhoid)

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

pathogenesis of enteric fever (typhoid)

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

43

Give an example of a disease without bacterial colonisation

food poisoning

44

true food poisoning (toxinoses) is

Consumption of food containing toxins (chemical or bacterial origin

45

Causative agent of botulism

Clostridium botulinum

46

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

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

47

Toxinoses of Staphylococcus aureus food poisoning

creamy foods, custards etc

48

Cause of Staphylococcus aureus food poisoning

enterotoxins

49

Symptoms of Staphylococcus aureus food poisoning

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

50

Bacillus cereus food poisoning
1) Aerobic/anaerobic?
2) spore forming/non spore forming?

1) obligately aerobic
2) spore forming

51

What are the two disease forms of Bacillus cereus?

1) emetic toxin
2) enterotoxins Nhe and HBL

52

Describe the emetic toxin disease form of Bacillus cereus

Heat stable
Short incubation

53

Describe the enterotoxins (Nhe and HBL) of Bacillus cereus

Heat liable
Diarrhoea form
Longer incubation