Lecture 1 Gram Positive

Question 1

Why do Gram Positive bacteria retain dye?

Answer 1

Thick peptidoglycan cell wall

Question 2

Why do Gram Negative bacteria not retain dye?

Answer 2

Thinner peptidoglycan cell wall layer

Question 3

What do Gram Positive Bacteria mainly comprise of?

Answer 3

Cocci, Bacilli or branching filaments

Question 4

Where are Staphylococcus found?

Answer 4

All over the skin, part of human’s natural flora

Question 5

How is Staphylococcus transmitted

Answer 5

Direct contact, fomites and medical instruments

Question 6

Are Staphylococcus opportunistic?

Answer 6

Yes

Question 7

Is Staphylococcus anaerobic or aerobic?

Answer 7

Anaerobic

Question 8

Describe the appearance of Staphylococcus

Answer 8

Spherical cells, grape like

Question 9

Why does Staphylococcus look like the way it is?

Answer 9

Due to cell division occurring successively on different planes, the daughter cells can remain attached

Question 10

What two Staphs cause disease?

Answer 10

S.aureus and S.epidermidis

Question 11

Which is more virulent, aureus or epidermidis?

Answer 11

Aureus

Question 12

What are the 4 features of Staphylococcus?

Answer 12

Non-motile
Salt tolerant
Tolerant to desiccation, radiation and 60 degrees on environment surfaces.
Produces catalase

Question 13

How does Protein A help S.aureus against the immune system?

Answer 13

Staph aureus is coated in Protein A. This binds to IgG stems and inhibits the complement cascade. By neutralising antibodies, this allows the bacteria to continue to persist and grow within the host body.

Question 14

How does coagulase help S.aureus against the immune system?

Answer 14

Produces coagulase that converts the fibrinogen into fibrin. Can then use this fibrin to form blood clots where it can hide inside. The blood clot provides a source of protection and a source of nutrients as it can break down the clot to access it’s amino acids.

Question 15

Which strain is opportunistic, aureus or epidermidis?

Answer 15

Both

Question 16

Stats on Staph epidermidis

Answer 16

Relies heavily on slime
Opportunistic- attached to urinary catheters (made of plastic), intravascular catheters - form biofilms

Question 17

What are the 4 enzymes that Staph Aureus can produce?

Answer 17

Hyaluronidase
Staphylokinase
Lipases
Beta lactamase

Question 18

What does hyaluronidase do?

Answer 18

Breaks down the hyaluronic acid. This is important to human cells as this acid is responsible in maintaining the hydration of the skin

Question 19

What does staphylokinase do?

Answer 19

Dissolves fibrin threads

Question 20

What does lipase do?

Answer 20

Digests lipids, giving staph aureus the ability to grow on skin and in cutaneous oil glands (acne).

Question 21

What does beta lactamase do?

Answer 21

Breaks down antibiotics and can stop them from working. This mutation can be passed to other staph aureus to increase antibiotic resistance

Question 22

What are the 4 types of toxins produced by Staphylococcus?

Answer 22

Cytolytic toxins
Exfoliative toxins
TSS toxins
Enterotoxins

Question 23

What do cytolytic toxins do?

Answer 23

Coded by genes, they disrupt the cytoplasmic membranes of cells including leukocytes

Question 24

What do exfoliative toxins do?

Answer 24

Dissolve intercellular bridge proteins causing skin sloughing

Question 25

What does the TSS toxin cause?

Answer 25

Toxic shock syndrome. Tampons are a common cause of this syndrome as they can both grow the staphylococcus and store the toxin

Question 26

What do enterotoxins do?

Answer 26

Causes vomiting associated with Staphylococcal food poisoning

Question 27

What status effects does Staph cause?

Answer 27

Systemic diseases
TSS: Fever, rash, low blood pressure and loss of skin
Bacteremia: Blood infection
Endocarditis
Pneumonia and empyema
Osteomyelitis

Question 28

Name 7 other Gram Positive Bacteria

Answer 28

Streptococci
Bacillus
Clostridium
Listeria
Corynebacteria
Mycobacteria
Propionibacteria