Microbiology 2 - Bacterial Diseases

Question 1

What are the two sources of bacteria?

Answer 1

Intrinsic - non-sterile sites inside the body, and extrinsic - outside the body.

Question 2

List the main intrinsic sources of bacteria

Answer 2

• Nasal cavity and sinuses
• Mouth
• Stomach
• Skin
• Lower genital tract
• SI/LI

Question 3

Define the term normal microbiota

Answer 3

The bacteria that are normally present inside the body.

Question 4

What are the two types of routes of entry of pathogens?

Answer 4

Expected - normal microbiota enter by an expected route (eg. From mother to baby)

Unexpected - normal microbiota entering at an unusual site/pathogens entering

Question 5

What is the pathway of bacteria acquired via the upper respiratory tract?

Answer 5

Infection in the upper respiratory tract (eg. Tonsillitis) to the adjacent tissues (brain, middle ear) to the bloodstream (or to the lower respiratory tract)

Question 6

Describe the pathway taken by bacteria that enter through the urogenital tract

Answer 6

UTI, genital tract infection, pregnancy related infection, and may spread to bloodstream

Question 7

What is an example of an extrinsic source of entry to the urogenital tract?

Answer 7

Bacteria entering through a catheter in hospital.

Question 8

What are the possible ways of a pathogen entering the skin?

Answer 8

• Wounds/surgery
• Skin diseases
• Injecting drugs
• Insect bites
• Cannulae

Question 9

What is the name for the route of entry through the gastrointestinal tract?

Answer 9

Faeco-oral route

Question 10

What are the possible consequences of infection acquired by the GI tract?

Answer 10

• Diarrhoeal illnesses
• Bacteremic infections
• Toxin mediated disease

Question 11

What are pathogens and what are their two types?

Answer 11

Pathogens are bacteria that cause disease - true pathogens always cause disease, opportunistic pathogens need specific conditions.

Question 12

What are commensals?

Answer 12

Bacteria that don’t cause disease

Question 13

Define infectivity

Answer 13

The general features favouring infection - infectious dose is the amount of a pathogen needed to cause a disease

Question 14

What factors contribute to pathogenicity?

Answer 14

• Transmission to a host
• Ability to colonise
• Motility
• Ability to replication speed
• Ability to avoid the immune system

Question 15

Define virulence.

Answer 15

Features that enhance disease causation

Question 16

What are the factors that affect virulence?

Answer 16

• Production of toxins
• Complete immune evasion
• Enzymes that degrade host molecules, or interrupt normal host processes

Question 17

List the main gram negative bacteria

Answer 17

• Neisseria
• Haemophilus influenzas
• Eschericha coli
• Salmonella
• Shingella
• Vibrio cholerae

Question 18

List the main gram positive bacteria

Answer 18

• Staphylococcus aureus
• Streptococcus
• Colostridum
• Listeria

Question 19

Give an example of some pathogens that infect by droplet transmission and what disease they cause

Answer 19

• Tonsilltis is caused by streptococcus pyogrnes

- Meningococcal septicaemia is caused by neisseria meningitidis

Question 20

Give some examples of bacteria that transmit to upper respiratory tract and what disease they cause.

Answer 20

• Strep pneumoniae causes pneumonia

- Also travels to the brain alongside strep milleri and haemophilus influenzae

Question 21

Give an example of a pathogen transmitted by faeco-oral transmission

Answer 21

Cholera - transmitted to Hati following hurricanes due to American soldiers.

Question 22

Give an example of transmission to the urogenital tract

Answer 22

• Group B steep infects neonates, from the GI tract of the mother
• Causes meningitis, septicaemia and death.

Question 23

Give some examples of pathogens that enter through the skin

Answer 23

S. aureus produces toxins that destroy neutrophils, leading in pus formation

Question 24

Define the infectious dose

Answer 24

The average number of organisms required to initiate infection.

Question 25

Define pathogenicity

Answer 25

Ability to cause disease

Question 26

List the main intrinsic routes of infection

Answer 26

• Broken skin
• Migration from naso-pharynx to lungs
• Gut to urinary tract

Question 27

List the main extrinsic routes of infection

Answer 27

• Water and food
• Coughs (droplet)
• Sexual transmission
• Nosocomial transmission (in hospitals)