classification of bacteria mw% +++++++

Question 1

What are the components of Aerobic Gram Positive cocci?

Answer 1

• Staphylococci (clusters)
• Streptococci and Enterococci (chains)

Question 2

What is the result of coagulase test in differentiating Staphlococci?

Answer 2

Coagulase-positive=Staphylococcus aureus which can be either MRSAor MSSA.

Coagulase negative=nothing

Question 3

Descibe the characteristics of Staphylococcus aureus?

Answer 3

• Commensal organism carried in nose, axilla, perineum.
• Wide range of disease from boils/abscesses and soa issue infections to septecaemia and osteomyelits.
• Commonly penicillin resistant due to production of penicillinase.
  *

Question 4

What are the coagulase-negative staphylococci?

Answer 4

• Many different species e.g. S. epidemidis
• Mainly skin commensals.
• Form biofilms and may be significant pathogens in the presence of foreign bodies/prostheses e.g. prosthe@c heart

Question 5

What are the properties of Streptococci?

Answer 5

• α- haemolytic (partial haemolysis)

-> turn blood agar green

• β-haemolytic (complete haemolysis)

-> turn blood agar clear

• Non haemolytic

Question 6

Give an example of α-haemolytic streptococci?

Answer 6

Streptococcus pneumoniae

-> pneumonia, meningitis, septecaemia

Question 7

What are the feutures of β-haemolytic streptococci?

Answer 7

• Further identified by carbohydrate surface antigens.
• further identified by Groups A-G.

• A, B, F and D clinically most important.

Question 8

What are the constituents of Gram positive bacilli?

Answer 8

• Aerobic
• Anaerobic:Clostridium tetani,Clostridium perfringens and Clostridium difficile.

Question 9

What are the feutures of Clostridium difficile?

Answer 9

• “Difficult” to culture.
• Asymptomaticc gut carriage in healthy people

. • Important cause of diarrhoea, associated with toxin production and potentially fatal

Question 10

What are the feutures of Clostridium perfringens?

Answer 10

• Found in soil and normal commensal in human and animal gut/faeces.
• Can contaminate food

Question 11

What are the feutures of Clostridium tetani?

Answer 11

• Toxin production by C. tetani cause tetanus.

• Uncontrolled muscle spasm due to loss of inhibition at neuromuscular junction.

Question 12

Gram negative flow chart

Answer 12

Question 13

Gram postive flow chart

Answer 13