Laboratory Part, Exam # 2 Flashcards
What characteristic differentiates genus Proteus from all the other Enterobacteriaceae?
urease positive
When a bacteria is said to be positive for gelatin test, it contains gelatinase. What does gelatinase do?
hydrolyzes gelatin
A TSI tube was inoculated with isolated culture from MAC. It yielded K/A. What does this mean?
only glucose was fermented
A SIM tube was inoculated with isolated culture from MAC. The said tube was incubated. After incubation, it became turbid, with black color & it turned red during indole test. What does this mean?
motile
H2S producing
indole positive
In Indole test, what reagent is involved?
Ehrlich’s reagent
Citrobacter often tests positive for Simmons citrate agar. What color does it yield?
blue
Which is false?
A. To isolate Salmonella, selenite F broth is used.
B. To isolate Salmonella, MacConkey agar is used.
C. Both are false.
D. Both are true.
A
False about Salmonella A.Most are non-motile B. Non-lactose fermenter C. Most produce H2S (slight production only) D. Form acid in glucose and mannose
A
What sort of colony growth is observed in Salmonella-Shigella agar, when Salmonella is inoculated?
colorless colonies with black centers
XLD is one of the media used in Salmonella culture. What does XLD stand for?
Xylose Lysine Desoxycholate
To isolate Salmonella, what specimen is usually obtained?
feces or rectal swab
False about Shigella
a. non-lactose fermenting
b. non-motile
c. able to produce gas from glucose
d. none of the above
C
EMB may be used to culture Salmonella and Shigella. What does EMB stand for?
Eosin Methylene Blue
False about E.coli A. positive for indole, MR and VP B. negative for H2S, urease and citrate C. may be motile or non-motile D. ferments mannitol, glucose and lactose
A
negative for VP
Since E.coli ferments lactose, what sort of colonies does one expect to see on MAC?
dry, pink colonies
Which biotype of V.cholerae 01 serogroup can hemolyze sheep RBC?
El Tor
Which will test positive for Voges-Proskauer, El Tor or Classical V.cholerae?
El Tor
Which is sensitive to Polymyxin B, El Tor or Classical V.cholerae?
Classical
Which is false about Klebsiella-Enterobacter-Serratia group?
A. non-motile
B. do not produce gas from glucose
C. positive for VP
C
A. All Enterobacteriaceae produce gas from glucose.
B. All Enterobacteriacea ferment glucose.
C. All Enterobacteriaceae are facultative anaerobes.
D. All Enterobacteriaceae are oxidase negative.
Which is false?
A
Purpose of MR-VP tests
determine which metabolic pathway is utilized by the Enterobacteriaceae species in question
A. Proteus species produce urease.
B. An Enterobacteriaceae species can be both MR+ and VP+
C. Proteus species are motile.
D. An Enterobacteriaceae species can be both MR- and VP-
Which is false?
B
action of gelatinase
hydrolyzes gelatin
reagents added to Voges-Proskauer test
alpha-naphthol
potassium hydroxide
False about Proteus
a. Positive in urease
b. Produces H2S
c. Negative in Phenylalanine deaminase
C
Reagents added to Nitrate Reduction Test
sulfanilic acid and α-naphthylamine
Which is false about Nitrate Reduction Test?
A. If the medium turns red after the addition of the nitrate reagents, it is considered a positive result for nitrate reduction.
B. If the medium does not turn red after the addition of the reagents, it only means that the organism was unable to reduce the nitrate.
C. If the tube turns red after the addition of the zinc, it means that unreduced nitrate was present. Therefore, a red color on the second step is a negative result.
B
If the medium does not turn red after the addition of the reagents, it can mean that the organism was unable to reduce the nitrate, or it could mean that the organism was able to denitrify the nitrate or nitrite to produce ammonia or molecular nitrogen. This is why Zn is added.
False about Enterobacter species
a. non-motile
b. rapid lactose fermenters
c. form pigmented colonies
d. has ornithine decarboxylase
A
