Public: The microbiota of a few organ systems

Question 1

What does the gastrointestinal tract consist of?

Answer 1

stomach, small intestine, and large intestine

Question 2

What are the functions of the gastrointestinal tract?

Answer 2

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

Question 3

How many microbial cells are in the GIT?

Answer 3

10^13 to 10^14 microbial cells

Question 4

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

Answer 4

Upper respiratory tract

The lower respiratory tract lacks microflora in healthy individuals

Question 5

Give examples of some microbiota in the upper respiratory tract

Answer 5

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

Question 6

Name the organs in the upper respiratory tract

Answer 6

sinuses, nasopharynx, pharynx, oral cavity, larynx

Question 7

Name the organs in the lower respiratory tract

Answer 7

trachea, bronchi, lungs

Question 8

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

Answer 8

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

Question 9

Which organisms commonly cause urinary tract infections in women?

Answer 9

E. coli and P. mirabilis

Question 10

What is the pH of the vagina like?

Answer 10

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

Question 11

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

Answer 11

Lactobacillus acidophilus

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

Question 12

Define virulence

Answer 12

the relative ability of a pathogen to cause disease

Question 13

How can virulence by measured?

Answer 13

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

Question 14

Define attenuation

Answer 14

The decrease or loss of virulence

Question 15

Define invasiveness

Answer 15

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

Question 16

What is the causative agent of diphtheria?

Answer 16

Corynebacterium diphtheriae

Question 17

Describe Corynebacterium diphtheria using the following points:

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

Answer 17

1) Gram positive
2) Motile
3) Clubbed morphology

Question 18

Clinical presentation of diphtheria

Answer 18

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

Question 19

Describe the pathogenesis of diphtheria

Answer 19

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

Question 20

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

Answer 20

Bordetella pertussis

Question 21

Describe Bordetella pertussis using these points:

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

Answer 21

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

Question 22

Clinical presentation of whooping cough (pertussis)

Answer 22

Paroxysms of cough (whoop)
CNS effects
Secondary pneumonia

Question 23

Describe the pathogenesis of whooping cough (pertussis)

Answer 23

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

Question 24

What are the 3 stages of pertussis disease progression?

Answer 24

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

Question 25

Describe the catarrhal stage of pertussis

Answer 25

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

Question 26

Describe the paroxysmal stage of pertussis

Answer 26

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)

Question 27

Describe the convalescent stage of pertussis

Answer 27

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

Question 28

What is the causative agent of Cholera?

Answer 28

Vibrio cholera

Question 29

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

Answer 29

comma shaped | gram negative

Question 30

Clinical presentation of severe cholera

Answer 30

Severe = rice water stools

Question 31

Pathogenesis of cholera

Answer 31

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?

Question 32

Name some non-invasive pathogens

Answer 32

Corynebacterium diphtheriae Bordetella pertussis Vibrio cholera

Question 33

Name some partially invasive pathogens

Answer 33

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

Question 34

Possible causative agents of Shigellosis?

Answer 34

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

Question 35

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

Answer 35

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

Question 36

Clinical presentation of shigellosis

Answer 36

Blood and puss in diarrhoea

Question 37

Pathogenesis of shigellosis

Answer 37

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.

Question 38

Name some primary invasive pathogens/diseses

Answer 38

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

Question 39

Causative agent of enteric fever (typhoid)

Answer 39

Salmonella enterica serovar Typhi | Primary invasive pathogen

Question 40

Clinical presentation of typhoid (enteric fever)

Answer 40

Systemic infection Constipation/diarrhoea Fever 3 week symptom duration 3% become chronic carriers

Question 41

Transmission of enteric fever (typhoid)

Answer 41

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)

Question 42

pathogenesis of enteric fever (typhoid)

Answer 42

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

Question 43

Give an example of a disease without bacterial colonisation

Answer 43

food poisoning

Question 44

true food poisoning (toxinoses) is

Answer 44

Consumption of food containing toxins (chemical or bacterial origin

Question 45

Causative agent of botulism

Answer 45

Clostridium botulinum

Question 46

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

Answer 46

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

Question 47

Toxinoses of Staphylococcus aureus food poisoning

Answer 47

creamy foods, custards etc

Question 48

Cause of Staphylococcus aureus food poisoning

Answer 48

enterotoxins

Question 49

Symptoms of Staphylococcus aureus food poisoning

Answer 49

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

Question 50

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

Answer 50

1) obligately aerobic | 2) spore forming

Question 51

What are the two disease forms of Bacillus cereus?

Answer 51

1) emetic toxin | 2) enterotoxins Nhe and HBL

Question 52

Describe the emetic toxin disease form of Bacillus cereus

Answer 52

Heat stable | Short incubation

Question 53

Describe the enterotoxins (Nhe and HBL) of Bacillus cereus

Answer 53

Heat liable Diarrhoea form Longer incubation