Classification of Pathogenic Bacteria 1

Question 1

What are the two types of Gram positive cocci?

Answer 1

• Streptococci (chains)

- Staphylococci (clusters)

Question 2

What test is used to further distinguish Staph. spp?

Answer 2

Coagulase test

Question 3

Staph. aureus shows what result in a coagulase test?

Answer 3

Positive

Question 4

Coagulase negative staph may be pathogenic in what circumstances?

Answer 4

In the presence of foreign bodies e.g. prosthetic heart valves, hip joints, pacemaker wires or in immunologically compromised patients

Question 5

How do we further distinguish Strep. spp? What are the three results of this test?

Answer 5

Haemolysis test -

alpha-haemolysis (partial) turns blood agar green

beta-haemolysis (complete) turns blood agar clear

Non haemolytic

Question 6

What are the examples of alpha-haemolytic gram positive bacteria?

Answer 6

Strep. pneumoniae - causes pneumonia, meningitis and septicaemia

Viridians strep. - causes infective endocarditis

Question 7

How are beta-haemolytic strep further classified?

Answer 7

Lancefield Groups A-G

Question 8

How are the Lancefield groupings determined? What are the most important groups?

Answer 8

Based on surface antigens - A, B and D are the most important clinically

Question 9

Give an example of Group A Strep

Answer 9

Strep. pyogenes - causes sore throats, cellulitis and necrotising fasciitis

Question 10

Give an example of Group B Strep

Answer 10

Strep. agalactiae - causes neonatal septic meningitis and bacteraemia and Genital tract carriage common

Question 11

Group D Strep is now classified as what?

Answer 11

Enterococcus spp

Question 12

How are Gram positive bacilli categorised?

Answer 12

Aerobic/Anaerobic

Question 13

What is an example of a Gram positive bacilli genus?

Answer 13

Clostridium spp