Lab 6: Microbiology Part 2

Question 1

What is the purpose of HEAT FIXING while preparing a Gram stain?

Answer 1

Kills BACTERIA and cause BACTERIAL CELLS to adhere to the slide

Question 2

What is the purpose of CRYSTAL VIOLET while preparing a Gram stain?

Answer 2

Stains PEPTIDOGLYCAN in BACTERIAL CELL WALL, especially thick layer in GRAM POSITIVE CELLS

Question 3

What is the purpose of GRAM’S IODINE while preparing a Gram stain?

Answer 3

Involves application of a MORDANT, which forms an insoluble complex with the CRYSTAL VIOLET, fixing the stain in the CELL WALL

Question 4

What is the purpose of ACETONE-ALCOHOL while preparing a Gram stain?

Answer 4

In GRAM POSITIVE CELLS, this will dehydrate the CELL, further trapping the CRYSTAL VIOLET-IODINE complex. In GRAM NEGATIVE CELLS this step dissolves the LIPOPOLYSACCHARIDE in the outer membrane and washes away excess stain from the surface of CELLS

Question 5

What is the purpose of SAFRANIN while preparing a Gram stain?

Answer 5

Stains the thinner PEPTIDOGLYCAN coat of GRAM NEGATIVE CELLS pink

Question 6

What general shape is seen in COCCI BACTERIA?

Answer 6

Round BACTERIA

Question 7

What general shape is seen in BACILLI BACTERIA?

Answer 7

Rod BACTERIA

Question 8

Define: ENTERIC

Answer 8

BACTERIA that live in the DIGESTIVE SYSTEM

Question 9

Define: AEROBIC

Answer 9

BACTERIA that require O2

Question 10

Define: ANAEROBIC

Answer 10

BACTERIA that don’t require O2

Question 11

Define: PATHOGENIC

Answer 11

BACTERIA that cause disease

Question 12

What could be concluded from a BAP (BLOOD AGAR PLATE) that has no visible colonies?

Answer 12

There is no BACTERIA present in the sample, or BACTERIA in the sample were killed

Question 13

What could be concluded from a BAP that has colonies on it, no change to the media surrounding it?

Answer 13

y-hemolytic, non-hemolytic

Question 14

What could be concluded from a BAP that has colonies on it, surrounding are has turned green?

Answer 14

a-hemolytic activity, partially hemolytic

Question 15

What could be concluded from a BAP that has colonies on it, surrounding area has become transparent?

Answer 15

b-hemolytic activity, completely hemolytic

Question 16

What could be concluded from a MAC (MACCONKEY AGAR PLATE) that has no colonies visible?

Answer 16

BACTERIA cannot grow in the presence of CRYSTAL VIOLET and bile salts; therefore BACTERIA are likely GRAM POSITIVE or NON-ENTERIC

Question 17

What could be concluded from a MAC (MACCONKEY AGAR PLATE) that has colonies visible?

Answer 17

BACTERIAL growth not affected by CRYSTAL VIOLET and bile salts; therefore BACTERIA are GRAM NEGATIVE and ENTERIC

Question 18

What could be concluded from a MAC (MACCONKEY AGAR PLATE) that has white colonies visible?

Answer 18

These GRAM NEGATIVE BACTERIA are also LACTOSE NEGATIVE. They cannot use LACTOSE and instead metabolize the PEPTONE in the media, forming ammonia and raising pH. Likely SALMONELLA or SHIGELLA

Question 19

What could be concluded from a MAC (MACCONKEY AGAR PLATE) that has pink colonies visible?

Answer 19

These GRAM NEGATIVE BACTERIA are also LACTOSE POSITIVE. They use LACTOSE, produce acid, and activate the neutral red dye. Likely E COLI or KLEBSIELLA

Question 20

True or false:

When interpreting a KIRBY-BAUER results table, the most effective ANTIBIOTIC will be the least sensitive

Answer 20

FALSE, other way around

Note: Sensitivity can be deducted by measuring the diameter of the clear zone around the ANTIBIOTIC

Question 21

List 3 factors that should be considered when determining an ANTIBIOTIC to treat BACTERIAL INFECTIONS

Answer 21

1. Allergies
2. Other meds
3. Cost

Question 22

What is a BROAD SPECTRUM ANTIBIOTIC?

Answer 22

An ANTIBIOTIC that treats a wide range of BACTERIAL INFECTIONS

Question 23

What is a NARROW SPECTRUM ANTIBIOTIC?

Answer 23

A specialized ANTIBIOTIC to treat a specific BACTERIA

Question 24

If there is only a small zone of inhibition around the ANTIBIOTIC DISC, the BACTERIA is ________ to the ANTIBIOTIC.

Answer 24

Resistant

Question 25

If there is a large zone of inhibition around the ANTIBIOTIC DISC, the BACTERIA is ________ to the ANTIBIOTIC.

Answer 25

Sensitive

Question 26

The prefix STREPTO indicates what?

Answer 26

That the BACTERIA are arranged in a line

Question 27

The prefix STAPHYLO indicates what?

Answer 27

That the BACTERIA are in a cluster