Introduction To Infection

Question 1

What is an infection?

Answer 1

Invasion of a host's tissue by microorganism 
AND
Disease caused by:
-microbial multiplication
-toxins
-host response

Question 2

What are the different ways in which someone can get infected? And give examples (4)

Answer 2

• From their own microbiota (UTI)
• physical contact, person to person (pneumonia)
• vectors, animals (malaria, swine flu)
• environment (water, food, air, surfaces)

Question 3

What are the 2 types of transmission and give some examples

Answer 3

Horizontal
-contact 
-inhalation
-ingestion (faecal-oral route)
Vertical
-mother to child
-before or at birth

Question 4

What are the two ways in which someone can inhale a pathogen?

Answer 4

Droplet

Aerosols

Question 5

What are the symptoms of infection? (5)

Answer 5

Rubor (redness)
Calor (heat)
Dolor (pain)
Tumor (swelling) 
Functio laesa (loss/disturbance of function)

Question 6

How do microroganisms cause disease?

Answer 6

Virulence factors; endo and exotoxins (cytolytic, AB toxins, superantigens, enzymes)
Host cellular damage; direct and consequent to host immune response

Question 7

How do we know if someone has an infection?

Answer 7

History -symptoms and potential exposures
Examination- organ dysfunction
Investigations- specific and supportive

Question 8

What are some examples of supportive investigations which help us know if someone have an infection?

Answer 8

• full blood count- neutrophils and lymphocytes
• CRP
• blood chemistry- liver and kidney function tests (UandEs)
• imaging-x-ray, ultrasound, mri
• Histopathology

**can repeat these tests throughout the management of the patient to check for improvement and worsening of symptoms

Question 9

What are some examples of bacteriological investigations that can be done to help determine whether someone has an infection?

Answer 9

• specimen types- swabs, fluids and tissues
• culture anything!!! - gram stains
• antigen detection
• nucleic acid detection

Question 10

How can we detect viruses?

Answer 10

Antigen detection (finding virus) - ELISA 
Antibody detection (patients repsonse)
Detecting viral nucleic acid (DNA/RNA)

Question 11

Give examples of disease determinants?

Answer 11

Pathogen: virulence factors, inoculum size, antimicrobial resistance

Patient; site of infection and co-morbidities (if you’re elderly/young/ diabetic etc)

Question 12

How would you prove that a disease is due to a microorganism?

Answer 12

1) the microorganism mist be found in abundance in all organisms suffering with the disease but should not be found in healthy organisms
2) the microorganisms must be isolated form a diseased organism and grown in pure culture
3) the cultured microorganism should cause disease when introduced into a healthy organism
4) the microorganism must be re-isolated from the inoculated diseased experimental host and identified as being identical to the original specific causative agent