Systematic Bacteriology II

Question 1

Virulence definition:

Answer 1

The risk of a microbe to cause damage to its host

Question 2

Pathogen definition:

Answer 2

A harmful organism that produces a pathology

Question 3

Commensal definition:

Answer 3

An organism that is part of the normal flora
Often a mutualistic relationship
Endogenous

Question 4

Opportunistic pathogen:

Answer 4

An organism that causes infection when opportunity/change in natural immunity arises

Question 5

What are coagulate tests used for?

Answer 5

To differentiate between Staph. aureus and coagulase negative Staph. (including Staph epidermis)

Question 6

What is haemolysis used for?

Answer 6

To identify and differentiate between ONLY streptococci

Question 7

2 types of Gram-negative cocci:

Answer 7

Neisseria meningitidis: most common cause of bacterial meningitis

Neisseria gonorrhoeae: gonorrhea

Question 8

Features of gut commensal coliforms:

Answer 8

Gram-negative cocci associated with GI tract

Many are part of normal bowl flora

Any coliform that gets into a normally sterile environment can cause infection e.g. UTI

Question 9

What is gentamicin?

Answer 9

First line antibiotic for the treatment of infections by coliforms

Question 10

What occurs during sepsis?

Answer 10

Small blood vessels become ‘leaky’ and lose fluid into tissues causing decreased blood volume so heart has to work harder

Poor tissue perfusion means blood supply to less essential organs is shut down

Question 11

How does sepsis increase the risk of haemorrhage?

Answer 11

Blood clotting system is activated
All clotting factors are used increasing haemorrhage risk

Question 12

What causes patients with gram negative sepsis to get very unwell?

Answer 12

Due to endotoxin released when Gram-negative bacteria die

Question 13

Gram positive pathogens (4):

Answer 13

Streptococcus
Enterococcus
Staphylococcus
Clostridia

Question 14

What does GAS stand for?

Answer 14

Group A Streptococci

Question 15

GAS associated diseases:

Answer 15

Scarlet fever
Impetigo

Question 16

Disease associated with streptococcus pneumoniae:

Answer 16

Pneumonia

Question 17

Staphylococcus epidermis:

Answer 17

Nosocomial
Coagulase negative

Question 18

Nosocomial definition:

Answer 18

Associated with foreign devices
E.g. catheters

Question 19

Staphylococcus aureus and what it
can cause:

Answer 19

Nosocomial and community
Coagulase positive (appears gold)
Clump forming (like grapes)

Causes:
- Skin, soft tissue and wound infection
- Sepsis

Question 20

Enterococcus:

Answer 20

Enteric infections

Part of normal bowel flora, can cause problems if they get into a normally sterile area

𝛾-haemolytic

Question 21

Clostridium spp:

Answer 21

Part of normal bowel flora

Produce endotoxins that can cause severe tissue damage

Question 22

Clostridium difficile:

Answer 22

Causes antibiotic-associated diarrhoea, especially in the elderly

Proliferates in the absence of normal flora

Question 23

Fever:

Answer 23

1. Antigen/LPS interacts with macrophages
2. Macrophages release cytokines into bloodstream
3. Cytokines travel to anterior hypothalamus
4. Prostaglandin E released - increases body’s thermal set point
5. Body perceives it as cold - starts to ‘shiver’
6. FEVER