Microbiology

Question 1

Antibiotic

Answer 1

Treat infections caused by bacteria

Question 2

Antiseptic

Answer 2

A substance used to stop or slow down the growth of microorganisms

Question 3

Disinfectant

Answer 3

A chemical liquid that destroys bacteria

Question 4

Aseptic

Answer 4

Aiming at the complete exclusion of harmful microorganisms

Question 5

Bactericidal

Answer 5

Agent that kills bacteria

Question 6

BacterIOSTATIC

Answer 6

Agent that prevents growth of bacteria

Question 7

incubation

Answer 7

Time it takes for an infection to develope after a person has been exposed to disease-causing organism.

Question 8

Normal flora

Answer 8

Microorganisms living on a surface (living or not) that do not cause disease and can even help prevent it.

Question 9

Nosocomial

Answer 9

Disease originating in a hospital

Question 10

H.A.I.

Answer 10

Infections associated infections from devices used during medical procedures.
- Catheters
- Ventilators
- Central lines

Question 11

Ubiquity of microorganisms

Answer 11

Microorganisms are ubiquitous in all kinds of micro- and macro-ecology environments on earth.

Question 12

Enteric

Answer 12

Bacteria that live in the digestive system of animals

Question 13

Aerobic

Answer 13

Bacteria that requires oxygen to grow

Question 14

Anaerobic

Answer 14

Bacteria that can grow in the absence of oxygen

Question 15

Pathogenic

Answer 15

Microorganisms that cause disease

Question 16

No colonies visible on BAP means?

Answer 16

No bacteria present in sample, bacteria killed during plate streaking process.

• blood agar is nutrient rich, should be able to grow anything… i think.

Question 17

Colonies grow on BAP. Media surrounding colonies still appears red. What does this mean?

Answer 17

• Microbe capable of using blood as a source of nutrition
• Incapable of damaging/lysis RBCs (gamma hemolysis/non hemolytic)

Question 18

Colonies present and surrounded by a green zone.

Answer 18

• microbe capable of using blood as a source of nutrition
• Capable of apathy-hemolysis/ partially hemolytic

Question 19

Colonies present and surrounded by a transparent, clear zone.

Answer 19

• microbe capable of using blood as a source of nutrition
• Capable of beat-hemolysis/complete hemolytic

Question 20

What does it mean if no colonies grow on an MAC plate?

Answer 20

Bacteria cannot grow in the presence of crystal violet and bile salts.
- bacteria GM+ and or non-enteric.

Question 21

What does it mean if bacteria grows on an MAC plate?

Answer 21

Bacteria is GM- and enteric

Question 22

What does it mean if colonies appear white on a MAC plate?

Answer 22

Bacteria are lac- (unable to ferment lactose) and metabolize the peptone in the media instead, forming ammonia, increase pH.

• salmonella
• shigella

Question 23

What does it mean id colonies appear pink/red on MAC plate?

Answer 23

Lac+, ferment lactose, producing acid, decreasing pH, activating neutral red dye.

• E. coli
• Klebsiella

Question 24

Function of crystal violet during GM stain?

Answer 24

Stains peptidoglycan in the bacterial cell wall, especially the thick later found in GM + cells.

Question 25

Function of Gram’s iodine during GM stain?

Answer 25

Involves application of a mordant, forms a insoluble complex with crystal violet, fixing the stain to the cell wall.

Question 26

Function of acetone-alcohol during GM stain?

Answer 26

Dehydrates the cell trapping the crystal violet/iodine complex.

In Gm- cells, this dissolves that lipopolysaccharide in the outermost membrane, washing away excess stain from the surface of the Gm- cells.

Question 27

Function of safranin during GM stains?

Answer 27

Stains the thinner peptidoglycan coat of Gm- cells pink.

Question 28

What does permissive formulated agar mean?

What does restrictive/selective agar mean?

Answer 28

Has the intent of allowing the growths of wearer organisms are present.

Only allows the growths of specific organisms. Ex. Including lactose so only enteric microorganisms can grow

Question 29

What do indicator plates do and how?

Answer 29

organisms are not selected on the basis of growth, but a compound in the agar is altered by the bacteria so as to change the colour of the colonies or the agar. Dyes can be used.

Question 30

Blood agar plates (BAP)

Answer 30

• contain mammalian blood (usually sheep), typically at a concentration of 5–10%.
• enriched media, used to isolate organisms which may require more nutrients than are provided in a regular nutrient agar plate
• differential media, as it is also used to detect hemolytic activity
• This type of agar is useful for the identification and culture of Streptococcus and Staphylococcus bacteria.

Question 31

MacConkey agar (MAC)

Answer 31

• culture medium designed to grow Gram-negative bacteria and stain them for lactose fermentation. (enteric bacteria)
• contains bile salts (to inhibit nonenteric bacteria), crystal violet dye (to inhibit Gram-positive bacteria), neutral red dye (which stains microbes fermenting lactose), lactose and peptone.
• Lac+ bacteria such as Escherichia coli and Klebsiella will produce acid, which lowers the pH of the agar below 6.8 and results in the appearance of red/pink colonies.
• Non-lactose fermenting bacteria such as Salmonella and Shigella cannot utilize lactose, and will use peptone instead. This forms ammonia, which raises the pH of the agar, and leads to the formation of white/colourless colonies.

Question 32

What are the steps to making a Gram stain?

Answer 32

1. Crystal violet (30 sec)
2. Rinse w/ distilled water (30 sec)
3. Grams iodine (60 sec)
4. Decolourize w/ acetone-alcohol
5. Rinse w/ distilled water (30 sec)
6. Counterstain w/ safranin (30 sec)
7. Decolourize w/ distilled water
8. Blot w/ bibulous paper