Week 2 - Gram Positive cocci

Question 1

Gram positive cocci that is present on most human skin?

Answer 1

Staphylococcus epidermidis

Question 2

Organism causing sore throats and severe skin infections?

Answer 2

Streptococcus pyogenes

Question 3

Another name for Streptococcus pyogenes

Answer 3

Group A Streptococcus

Question 4

Gram positive cocci that is present on 30% of human skin, causes some infections

Answer 4

Staphylococcus aureus

Question 5

Gram positive cocci that is pathogenic to newborn babies

Answer 5

Streptococcus agalactiae

Question 6

Streptococcus-like organism that is an environmental pathogen

Answer 6

Enterococcus spp

Question 7

Gram positive cocci that causes urinary tract infections

Answer 7

Staphylococcus saprophyticus

Question 8

Lancefield group for Enterococcus faecalis

Answer 8

Group D

Question 9

Gram positive cocci responsible for pneumonia, meningitis and inner ear infections

Answer 9

Streptococcus pneumoniae

Question 10

What diseases can Enterococcus faecalis cause?

Answer 10

• Urinary Tract Infections
• Surgical Wound infections
• Endocarditis

Question 11

What medical problems can Staphylococcus epidermidis cause?

Answer 11

• Sepsis (esp preterm infants)
• Osteomyelitis
• Biofilms in catheters/surgical implants

Question 12

What type of haemolysis does Staphylococcus epidermidis have?

Answer 12

None (Gamma)

Question 13

I am a Gram positive bacterium who is catalase positive and coagulase negative. Who am I and what identifying antibiotic am I sensitive to?

Answer 13

• Staphylococcus epidermidis

- Novabiacin Sensitive

Question 14

I am a Beta-haemolytic, Gram positive cocci who is catalase positive and coagulase positive. Who am I and what colour would my colonies be seen on Mannitol Salt Agar?

Answer 14

• Staphylococcus aureus
• YELLOW colonies on MSA because I utilise Mannitol (halophile) creating acid that causes a pH change in the agar - changing the colour indicator from red to yellow.

Question 15

I am a Gamma-haemolytic, Gram positive cocci who is catalase positive and coagulase negative. I am Novobiacin resistant. Who am I and what colour would my colonies be on CLED agar and MSA agar?

Answer 15

• Staphylococcus saprophyticus
• Yellow on CLED - fermentation of lactose creates acid that causes pH change and colour indicator goes from blue to yellow
• Red on MSA - I will grow on MSA but I won’t utilise the mannitol salt, meaning there will be no pH change, no acid production and colour indicator will stay red.

Question 16

What diseases can Streptococcus pyogenes cause?

Answer 16

• Strep Throat
• Scarlet Fever
• Guttate psoriasis
• Necrotising Fasciitis
• Rhematic Fever
• TSS
• Peurperal sepsis
• Osteomyelitis
• Septicaemia
• Arthritis…

Question 17

What toxins does Strep A produces?

Answer 17

Erythrogenic toxin - scarlet fever

Pyrogenic toxins - Fever and TSS

Question 18

I am an Alpha-haemolytic, Gram positive cocci who is catalase negative and Optochin sensitive. Who am I, what Lancefield group am I and what diseases can I cause?

Answer 18

Streptococcus pneumoniae:

• NO LANCEFIELD GROUPING
• otitis media
• wet pneumonia
• meningitis

Question 19

What virulence factors does Streptococcus pyogenes have?

Answer 19

• Cell envelope proteinase (degrades some cytokines and reduces neutrophil activation)
• Hyaluronidase - breaks down connective tissue
• Immunoglobulin protease
• Collagenases