Bacteria Agars and visual identification

Question 1

What medium / media can be used to isolate 0157, Shiga toxin producing E. coli (STEC) strain?

Answer 1

Sorbitol MacConkey agar

Question 2

Doing campylobacter plates your manager forgets to order more plates. What alternative can you use instead of campylobacter blood agar?

Answer 2

Hektoen enteric (HE) agar or HEA

Question 3

What media is used to isolate vibrio cholerae?

Answer 3

Bile salt agar or TCBS, thiosulphate citrate bile salts sucrose agar

Question 4

What media is selective for enterococcus species?

Answer 4

Bile esculin agar - contains 40% bile

Question 5

What media allows bacteria to demonstrate their hemolytic properties?

Answer 5

Blood agar
Staphylococcus aureus: ß-Hemolytic;
Streptococcus pneumonia and S viridans: a-Hemolytic;
Enterococcus: Non-Hemolytic

Question 6

What media is used to isolate bordetella pertussis?

Answer 6

Bordet - Gengou Agar
Charcoal Blood Agar
Regan - Lowe Medium
Note: Charcoal important in these agars to neutralize fatty acids and peroxide which are toxic to bordetella

Question 7

What media is used to isolate Legionella?

Answer 7

Buffered charcoal yeast agar (BCYA)

Question 8

What media is used for isolate of clostridium difficile?

Answer 8

Cefoxitin cycloserine Fructose agar (CCFA) or Cefoxitin cycloserine Egg Yolk Agar

Question 9

What media is used to isolate Yersinia?

Answer 9

CIN, Cefsulodin - Irgasan - Novobiocin medium
Note: It can be used to isolate Aeromonas too!

Question 10

CNA, Columbia - Colistin Nalidixic acid agar will isolate what kind of bacterias?

Answer 10

Gram positive cocci

Question 11

What media isolates streptococcus pyogenes?

Answer 11

Crystal violet blood agar

Question 12

What media is used to detect lipase and lecithinase activity in a bacterias from the clostridium genus?

Answer 12

Egg yolk agar

Question 13

Chocolate agar is useful for what kind of bacterias?

Answer 13

fastidious organisms such as hemophilus (X/V factor requirements), Neisseria gonorrhoeae, and S. pneumoniae

Question 14

What media is used to grow corynebacterium?

Answer 14

Loeffler slant. It stimulates metachromatic granules in Corynebacterium diphtheriae

Question 15

What two medias are selective for mycobacterium?

Answer 15

Lowenstein-Jensen medium, middlebrook 7H10 agar, and Petragnani agar

Question 16

What media is useful for differentiating enterobacteriaceae?

Answer 16

MacConkey Agar -> Lactose fermenters and non-lactose fermenters. All members of the family ferment glucose.

Question 17

List media that are useful for differentiating Salmonella and Shigella from stool specimens?

Answer 17

MacConkey Bile Salt Lactose Agar (Not sure if we need to know)
Hektoen Enteric (HE) agar -> (Shigella flexneri are green / transparent colonies. Salmonella will be black colonies)
Salmonella - Shigella (SS) agar

Question 18

What media is selective and indicator for S. aureus?

Answer 18

Mannitol salt agar

Question 19

What is the agar of choice for antimicrobial susceptibility for bacteria?

Answer 19

Mueller - Hinton Agar

Question 20

What is the media of choice for isolating campylobacter?

Answer 20

Skirrow’s Campylobacter medium
Campy Blood Agar
HE agar (alternative)

Question 21

Selenite F broth is useful for isolating what kind of bacterias from stool samples?

Answer 21

Shigella and Salmonella

Question 22

What media is useful for isolating Neisseria gonorrhoeae and Neisseria meningitidis?

Answer 22

Thayer - Martin Medium. It contains vancomycin, colistin, and nystatin

Question 23

What would vibrio cholerae colonies look like on TCBS agar?

Answer 23

Yellow colonies would be vibrio cholerae. Vibrio parahaemolyticus would be green colonies. V. cholerae is able to ferment sucrose turning bromthymol (dye) from blue to yellow.

Question 24

What would lactose fermenters and nonfermenters look like on MacConkey agar?

Answer 24

Lactose fermenters would be pink while non lactose fermenters would be clear or yellow.

Question 25

On Hektoen enteric agar, what would salmonella and shigella look like?

Answer 25

Salmonella - black colonies (made so by production of H2S) Shigella - Green colonies b/c of peptone metabolism increasing the pH (media color turns blue) Other bacterias will be orange colonies (not shigella or salmonella) due to lactose fermentation. These orange colonies could be E. coli, K. pneumonia, and yersinia enterocolitica.

Question 26

What does calcofluor stain target in fungi?

Answer 26

Chitin and cellulose.

Question 27

What media is used to grow Francisella tularensis?

Answer 27

Cystine - Glucose Agar

Question 28

What bacteria is isolated with skirrow agar?

Answer 28

Helicobacter pylori

Question 29

What bacteria is isolated with cystine tellurite blood (tinsdale) agar and loeffler's medium?

Answer 29

Corynebacterium diphtheriae

Question 30

What is the difference in bacteria culture between cystine tellurite blood (tinsdale) and loeffler's medium?

Answer 30

Loeffler's medium enhances metachromatic granule formation. On Cystine tellurite blood agar the C. diphtheriae colonies will be black. Not sure what colony growth is like on tinsdale agar.

Question 31

What kind of bacteria is isolated from BBE agar?

Answer 31

Bacteroides fragilis group -> black colonies

Question 32

KVLB agar is used to isolate what bacteria?

Answer 32

Bacteroides species. The agar enhances pigment production.

Question 33

CCFA agar or cycloserine - cefoxitin fructose agar is used to isolate what bacteria?

Answer 33

Clostridium difficle

Question 34

CDC anaerobic blood agar is enriched with what kind of nutrients for anaerobes?

Answer 34

Hemin, cystine, and vitamin K