Micro Bio Quiz 5

Mannitol Salt Agar

Purpose: To presumptively identify Stapyhlococcus aureus and select for the growth of salt-tolerant bacteria

What is folliculitis? (1st level of staph infection)

Infected hair follicle (pimple)

What is an abscess? (2nd level of staph infection)

Localized region of pus surrounded by inflamed tissue

What is a furuncle? (3rd level of staph infection)

Multiple local focal points of infection (boils)

What is a carbuncle? (4th level of staph infection)

Deep in the tissue (causes fever)

What does yellow growth on the agar in the MSA test mean?

(+) result, acidic, fermented mannitol & produced acids

Growth = osmotolerant

Possible S. aureus (confirmed w/ coagulase test)

What does red/pink growth on the agar in the MSA test mean?

(-) result, alkaline, did NOT ferment mannitol

Growth = Osmotolerant

Not S. aureus, possible S. epidermis

What does no growth on the agar in the MSA test mean?

No osmotolerant bacteria

What is the pH indicator in the MSA test?

Phenol red:
Yellow = acidic

Orange = neutral

Red = alkaline

What are the selective & differential ingredients in MSA?

Mannitol = differential

NaCl = selective for osmotolerant bacteria

What are the three virulence factors of Staph?

1) Coagulase - forms clot (97% of Staph)

2) B-hemolysin - digests red blood cells

3) Staphylokinase - dissolves clot

What is Beta-hemolysis? (throat culture)

Complete destruction of RBC

Group A & Group B Strep

What is Alpha-hemolysis? (Throat culture)

Partial destruction of RBC (S. pneumoniae)

What is Gamma-hemolysis? (Throat culture)

No damage to RBC (S. mutans & Group D strep)

What is purpose of CAMP test?

To identify & confirm the presence of Group B Strep

Streptococcus pyogenes (CAMP)

Sensitive to bacitracin, Beta hemolysis

Streptococcus pneumoniae (CAMP)

Sensitive to optochin, Alpha hemolysis

Streptococcus agalactiae (CAMP)

CAMP (+), Beta hemolysis

Streptococcus mutans (CAMP)

Gamma hemolysis

Enterococcus faecalis (CAMP)

Bile Esculin (+), Gamma hemolysis

What is the purpose of the coagulase test?

To determine if bacteria can produce coagulase (confirmatory test)

Is coagulase and endoenzyme or exoenzyme?

Exoenzyme

What does fibrinogen do? (Coagulase test)

clotting factor in liquid part of blood

What does a (+) coagulase test look like?

(+) = solid, coagulase present, S. aureus

What does a (-) coagulase test look like?

(-) = liquid, coagulase absent

What is the purpose of the catalase test?

To test bacteria for the catalase enzyme

What is a (+) result in catalase test?

(+) = bubbles

Catalase broke down H2O2 (O2 produced

What is a (-) result in catalase test?

(-) = no bubbles

Catalase did NOT break down H2O2 (NO O2 produced)