Gram Positive Bacteria

Question 1

What is the Structure of the Gram Positive Bacteria Wall?

Answer 1

A thick peptidoglycan wall which stains purple on gram staining as it retains the dye very well.
Only 1 membrane: Cytoplasmic Membrane
Also contains Polysaccharides.

Question 2

What is the Structure of the Gram Negative Bacteria Wall?

Answer 2

A thin Peptidoglycan wall which stains pink as it does not retain the dye as well in gram staining.
Has 2 Membranes: Outer Membrane and Inner Cytoplasmic Membrane.
Also contains Lipopolysaccharides and Porins.

Question 3

What do you call Gram Positive Circular Bacteria in Bunches?

Answer 3

Staphylococci

Question 4

What do you call Gram Positive Circular Bacteria in Chains?

Answer 4

Streptococci

Question 5

Give examples of Staphylococci

Answer 5

Staph. Epidermis

Staph. Aureus

Question 6

How do you differentiate between Staph. Epidermis and Staph. Aureus?

Answer 6

Staph. Aureus is Coagulase Positive

Staph. Epidermis is Coagulase Negative

Question 7

Give Examples of Streptococci

Answer 7

Strep. Viridans (Many strains, not a single bacteria)
Strep. Pneumoniae
Strep. Pyogenes (Group A)
Strep. Agalactaiae (Group B)
Enterococcus Species e.g. Enterococcus Faecalis

Question 8

Which Streptococci are Alpha Haemolytic?

Answer 8

Strep. Viridans (Many strains, not a single bacteria)

Strep. Pneumoniae

Question 9

Which Streptococci are Beta Haemolytic?

Answer 9

Strep. Pyogenes (Group A)

Strep. Agalactaiae (Group B)

Question 10

Which Streptococci are Gamma Haemolytic?

Answer 10

Enterococcus Species e.g. Enterococcus Faecalis

Question 11

What do you call Rod-Shaped Bacteria?

Answer 11

Bacilli

Question 12

How are the Bacilli Bacteria categorised?

Answer 12

Small and Large Bacilli

Question 13

Give examples of Small Bacilli

Answer 13

Corynebacterium Diphtheriae
Diphtheroids (also part of the Corynebacterium Species)
Listeria Monocytogenes

Question 14

Give examples of Large Bacilli

Answer 14

Bacillus Species e.g. Bacillus Cereus and Bacillus Anthracis

Question 15

How are Spiral-Shaped Bacteria Categorised?

Answer 15

Spirochete (longer and more flexible due to flagellum component)
Spirilla (shorter and more rigid)

Question 16

Give examples of Anaerobic Cocci

Answer 16

Anaerobic Strep.

Question 17

Give examples of Anaerobic Bacilli

Answer 17

Clostridium species

Question 18

What agar is used to grow Streptococci?

Answer 18

Blood Agar - think Haemolysis!

Question 19

What is the Classification System used to group Strep. Group A and B bacteria?

Answer 19

Lancefield Grouping

Note that there is NO Lancefield Group for Strep. Pneumoniae and Viridans

Question 20

Which Strep. Species is associated with Endocarditis?

Answer 20

Strep. Bovis/Gallollyticus

Needs to be investigated with colonoscopy as it has carcinoma links.

Question 21

What is MRSA?

Answer 21

Methicillin-Resistant Staph. Aureus (can also be sometimes resistant to Gentamicin)
Therefore, treated with Vancomycin

Question 22

What is MSSA?

Answer 22

Methicillin-Susceptible Staph. Aureus

Repeat Blood Cultures after 2-3 days if found

Question 23

Which Clostridium Species is associated with Wound Infections?

Answer 23

Clostridium Perfringens

Question 24

Which Gram Positive bacteria is heavily associated with Gastroenteritis from reheated rice left on the counter?

Answer 24

Bacillus Cereus

Question 25

What should you consider if you find Staph. Epidermis in a Blood Culture?

Answer 25

Possible contamination when taking blood culture (is a skin commensal)
Only truly worrisome for Endocarditis