Microbiology: Lab 1

Question 1

Enterobacteriaceae are facultative anaerobes, ferment glucose, have peritrichous or no flagella oxidase-negative, nitrate to nitrite, Which ones are lactose fermenters?

Answer 1

E. coli
Klebsiella pneumoniae
Enterobacter
Serratia
Citrobacter

Question 2

Name the non-lactose fermenting Enterobacteriaceae?

Answer 2

Salmonella typhi
Salmonella typhimurium
Shigella
Proteus
Morganella
Yersinia pestis/enterolitica
Edswardsiella, Hafnia (opportunists)

Question 3

Curved rods, Facultative anaerobes, ferment sugars, have polar flagella, oxidase-positive, Name the species?

Answer 3

Vibrio Cholerae/parahemolyticus
Campylobacter
Aeromonas
Plesiomonas

Non-fermenter = Pseudomonadaceae

Question 4

How can the IMViC reactions be used to differentiate fecal coliforms?

Answer 4

E. coli = Indole+, Methyl red+,

Enterobacter and Klebsiella = Voges-Proskauer+, Citrate+

Question 5

What is McConkey agar?

Answer 5

Agar that has bile salts and crystal violet to kill gram+ species. It has Lactose and a pH indicator to differentiate between lactose and non-lactose fermenting organisms.

Question 6

Name 3 anaerobes that cause GI tract disease?

Answer 6

C. perfringens
C. difficile
C. botulinum

Question 7

What is Eosin Methylene Blue agar?

Answer 7

EMB is a semi-selective and differential medium for preliminary identification of enteric gram- rods.

Stong lactose fermenting E. coli produce
Weaker acid forming Kelbsiella produce purple colonies.
Non-lactose fermenting Salmonella produce

Question 8

What is Salmonella-Shigella agar?

Answer 8

Highly selective agar for Salmonella-shigella.

Non-lactose fermenters form
Uninhibited Lac+ species form pink colonies
Salmonella = pink with black center.

Question 9

Describe the results of a gram stain?

Answer 9

Gram negative colonies will be pink

Gram positive colonies will be purple

Question 10

What is the Kligler’s Iron Agar (KIA) test?

Answer 10

KIA detects fermentation of glucose and lactose. Red slant = only glucose fermentation
Yellow slant = Lactose fermentation

Detects H2S which occurs with metabolism of cysteine, cystine, and methionine.

Salmonella =
Shigella =
E. coli =
Non-fermenter =

Question 11

KIA with alkaline red slant and alkaline red but?

Answer 11

No carbohydrate fermentation = Non-fermentive bacteria P. aeruginosa

Question 12

KIA with Alkaline red slant, acid yellow butt, no gas?

Answer 12

Glucose is fermented but lactose is not fermented.

Shigella

Question 13

KIA with Alkaline red slant, acid H2S butt (black) butt and gas?

Answer 13

Glucose is fermented but lactose is not fermented. H2S usually formed.

Salmonella, Citrobacter, Proteus

Question 14

KIA with acid yellow slant, Acid yellow butt and gas?

Answer 14

Lactose is fermented

E.coli, Klebsiella, Enterobacter.

Question 15

What is the Indole test?

Answer 15

Detects the conversion of tryptophan into indole.
Kovacs reagent reacts with indole to produce red product.

Positive = Shigella
Negative = Salmonella

Question 16

What is the urease test and which genus is it significant for?

Answer 16

Detects the hydrolysis of urea to ammonia. Positive reaction = red color on slant of agar

Strongly positive for proteus

Question 17

Which species are non-motile and which is only motile at room temperature?

Answer 17

Klebsiella and _______ are non motile
Yersinia are only motile at room temperature
Pseudomonas only shows motility near top of agar where oxygen is plentiful (strict aerobe)

Question 18

Which enteric exhibits characteristic swarming?

Answer 18

_____________

Question 19

What is the Kirby-Bauer method?

Answer 19

Tests antibiotic sensitivity