Systemic Bacteriology pt.2

Question 1

Define:

• Endogenous microorganisms

- Exogenous microorganisms

Answer 1

Endogenous - Internal

Exogenous - External

Question 2

Define virulence

Answer 2

The capacity of a microbe to cause damage to the host

Question 3

Define a pathogen

Answer 3

• Harmful microbe
• Produces a pathology
• Is virulent

Question 4

Define commensal

Answer 4

• Microbe is part of the normal flora

- Microbe benefits, host is unaffected

Question 5

Define mutualistic

Answer 5

• Microbe is part of the normal flora

- Microbe and host both benefits

Question 6

Define an opportunistic pathogen

Answer 6

A pathogen that causes an infection when an opportunity (change in the normal) arises

Question 7

Give an example of a change that can allow for an opportunistic pathogen to cause damage

Answer 7

Broad spectrum antibiotics wipe out gut flora
–>
The competition no longer keeps a microbe under check
–>
It proliferates becoming a pathogen

Question 8

Give examples of infectious agents

Answer 8

Bacteria, Viruses, Fungi, Protozoa, Parasites, Prions

Question 9

Describe the basic pathogenesis of an infectious disease

Answer 9

Pathogen transmitted from reservoir to host
-->
Colonises
-->
Evades host defences
-->
Multiplies & Completes its life cycle
--> 
Exits the host

Question 10

Give an example of pathogenic fungi

When can it easily precipitate

Answer 10

Candida spp.

Can precipitate if competitor microorganisms are killed e.g. after antibiotics

Question 11

Give an example of a protozoan disease

Answer 11

Malaria, toxoplasma

Question 12

Give examples of common gram -ve pathogens

Answer 12

• Neisseria spp. (cocci)

- Escherichia spp. (bacilli)

Question 13

Give examples of common gram +ve pathogens

Answer 13

• Streptococcus spp. (cocci)
• Staphylococcus spp. (cocci)
• Enterococcus spp. (cocci)
• Clostridium (bacilli)

Question 14

Give examples of gram -ve cocci

Answer 14

• Neisseria meningitidis

- Neisseria gonorrhoeae

Question 15

Define coliforms

Answer 15

• Gram -ve bacilli
• Part of normal bowel flora
• Grow best aerobically

Question 16

Under what circumstance are coliform bacteria dangerous?

Answer 16

If they infect a normally sterile environment e.g.

• Peritonitis
• Biliary tract infection

Question 17

Why is gram -ve sepsis sepsis particularly bad?

Answer 17

The endotoxin (lipopolysaccharide) released from the gram -ve cell wall when the bacteria dies can cause Systemic Inflammatory Response Syndrome (SIRS)

Question 18

Describe the cause of Systemic Inflammatory Response Syndrome (SIRS) by gram -ve bacteria

Answer 18

The lipopolysaccharides and peptidoglycan stimulate macrophages, B cells, and others
–>
They release inflammatory cytokines

Question 19

What happens to capillaries during sepsis?

Answer 19

They become “leaky” and lose fluid into tissues

Question 20

Describe the impact of capillaries “leaking” during sepsis on organs

Answer 20

Lower blood volume
–>
Heart rate increased to maintain tissue perfusion
–>
Poor tissue perfusion causes less essential organs to shut down

Question 21

Describe the impact of capillaries “leaking” during sepsis on haemorrhage risk

Answer 21

Blood clotting system activated
-->
Clotting in capillaries
-->
Uses up all of the clotting factors
--> 
Increased risk of haemorrhage

Question 22

State the progression of infection to septic shock

Answer 22

Infection
-->
Sepsis
-->
Severe Sepsis
-->
Septic Shock

Question 23

Define fever?

What is normal core temp?

Answer 23

Fever is a core temp >38 degrees celsius

Normal body temp is 37

Question 24

Describe the purpose of a fever

Answer 24

Raising the core temp is beneficial for fighting infection

Question 25

Describe the mechanism of fever production

Answer 25

Antigens interact with macrophages --> Macrophages release cytokines into the blood --> Cytokines go to anterior hypothalamus --> Prostaglandin E is released which increases the bodies thermal set point

Question 26

For which species of bacteria in haemolysis important in its identification?

Answer 26

Streptococcal Haemolysis is only important for the classification of streptococci

Question 27

Describe group A streptococci (GAS)

Answer 27

Gram -ve Cocci β Haemolytic Lancefield Grouping - A *Called Group A Streptococcus (GAS)

Question 28

Give examples of streptococcal bacteria

Answer 28

GAS - Streptococcus pyogenes Streptococcus pneumoniae

Question 29

Describe streptococcus pneumoniae

Answer 29

Gram +ve Cocci α-haemolytic Causes pneumonia

Question 30

Give an example of a non-haemolytic streptococci

Answer 30

Enterococci

Question 31

Describe staphylococci

Answer 31

Gram +ve Cocci Appear in clusters Can be coagulase -ve or +ve

Question 32

Give 2 examples of staphylococci and state their coagulase status

Answer 32

S. aureus: coagulase +ve S. epidermidis: coagulase -ve

Question 33

What does MRSA stand for? Describe it

Answer 33

Methicillin-resistant Staphylococcus aureus Gram +ve Cocci Appear in clusters Coagulase +ve

Question 34

Give an example of an anaerobic gram positive bacteria

Answer 34

Clostridium spp. e.g. Clostridium difficile

Question 35

Describe clostridium spp.

Answer 35

Gram +ve Bacilli Produce spores

Question 36

When do clostridium difficile infections usually occur?

Answer 36

In the absence of normal gut flora e.g. After antibiotics have wiped out normal flora