Question

Lab Practical #1 On-line Determination of Bacteria.

In this lab exercise you will be given the bacteria and you will need to explain what it would look like on the different medias (NG is suitable for No growth).

BA=blood agar, CNA = Columbia nutrient agar, MA=MacConkey agar, MSA=mannitol salt agar, HE=Hektoen enteric Agar

Staphylococcus Aureus: Gram stain __________________. Growth on Media: BA _________ CNA__________ MA__________MSA_________HE__________ One place where the bacteria causes infection ________.

Streptococcus pneumoniae: Gram stain __________________. Growth on Media: BA _________ CNA__________ MA__________MSA_________HE__________ One place where the bacteria causes infection ________.

Escherichia coli: Gram stain __________________. Growth on Media: BA _________ CNA__________ MA__________MSA_________HE__________ One place where the bacteria causes infection ________.

Proteus mirabilis: Gram stain __________________. Growth on Media: BA _________ CNA__________ MA__________MSA_________HE__________ One place where the bacteria causes infection ________.

Salmonella enterica: Gram stain __________________. Growth on Media: BA _________ CNA__________ MA__________MSA_________HE__________ One place where the bacteria causes infection ________.

PLEASE TYPE. No handwritting.

Answer 1

Answer:

1) Staphylococcus aureus:

a) Gram Stain :- Gram positive

b) BA :- Beta Hemolysis with Round, yellow colonies

c) CNA :- Growth with large, yellow-cream colonies

d) MA :- No Growth

e) MSA :- Growth with large colonies and turn media Yellow

f) HE :- No Growth

g) One place of infection :- Heart valves

2) Streptococcus pneumoniae:

a) Gram stain :- Gram positive

b) BA :- Small colonies with green sheen (Alpha hemolysis)

c) CNA :- Small greenish colonies

d) MA :- No growth

e) MSA :- No growth

f) HE :- No growth

g) Place of infection :- Ear

3) Escherichia coli:

a) Gram stain :- Gram negative

b) BA :- Growth White colonies without hemolysis.

c) CNA :- No growth

d) MA :- Heavy growth with Dark pink colonies

e) MSA :- No growth

f) HE :- Growth with Yellow-orange colonies

g) Place of infection :- Urinary tract

4) Proteus mirabilis:

a) Gram stain :- Gram negative

b) BA :- Growth in a concentric circles form (wave like) and beta hemolysis

c) CNA :- No growth

d) MA :- Smooth pale, colourless colonies with no wave formation

e) MSA :- No Growth

f) HA :- Small, dark centered and greenish colonies

g) One place of infection :- Urinary tract

5) Salmonella enterica:

a) Gram stain :- Gram negative

b) BA :- Growth with Beta Hemolysis

c) CNA :- No Growth

d) MA :- Growth with pale Yellow colonies

e) MSA :- No Growth

f) HE :- Growth with blue-greeblue-green colonies

g) Place of infection :- Intestine

Explanation :-

Blood agar :-

• Blood agar is supplemented with sheep blood.
• Ability of bacteria to lyse RBCs is checked by this method.
• Bacteria which have an enzyme called Hemolysin can do Hemolysis while those who do not have it, are unable to do so.

CNA agar :-

• CNA agar is also like blood agar but it inhibits the growth of Gram negative bacteria.
• It is supplemented with Nalidixic acid and Colistin which inhibits the growth of Gram negative bacteria.

Macconkey Agar:-

• Macconkey Agar is a Selective, differential media too.
• It selects for only Gram negative and enteric bacilli, all other type of bacteria can not grow in this.
• The Colour changes is due to ability of lactose fermentation. A pH indicator is used.

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