Enterobacteriaceae Flashcards
Reactions and Growth Patterns
What does the Vitek system measure? What organisms does it measure?
microbial identification and antibiotic susceptibility testing
a suspension of the test organism is prepared in saline, test cards are then utilized based on testing needs
Strep, Staph, GNB, enterococci, and yeast
What kinds of organisms does API 20E measure?
Gram negative, oxidase NEG bacteria
How does the Maldi-ToF work?
mass spectrometry: chemical compounds are ionized into charged particles and the ratio of their mass to charge is measured.
MALDI-TOF stands for matrix-assisted laser desorption ionization and Time of Flight, where the time for required for ions to travel the length of the flight tube is measured and can be used to generate a characteristic spectrum based on the mass to charge ratios of proteins and peptide fragments.
How does MicroScan work?
Automated program for IDing bacteria by use of simultaneous inoculation of all 96 wells of the panel
What 4 enterobacteriaceae are H2S producers?
some Provedencia spp.
Edwardsiella tarta
Salmonella spp.
Proteus spp.
What two things make up lactose, and what two things are needed for utilization?
Glucose and galactose
needs permease and beta-galactosidase
ONPG is similar to lactose, except it’s made from galactose and what other thing? Does it require permease?
What is a positive color, and what’s a negative one?
made from galactose and orthonitrophemol
Only uses beta-galactosidase
Pos: yellow
Neg: no color change
What 8 media have a H2S system?
Salmonella-Shigella
XLD
Hektoen Enteric
BS
KIA
LIA
TSI
SIM
KIA detects for the fermentation of what two sugars? What do K and A stand for, what are the colors associated with each, and what do K/A, A/A, and K/K mean?
looks for glucose and lactose only
K = alkaline (red)
A = acid (yellow)
K/A = glucose fermented (yellow butt) and lactose did not (red slant)
A/A = both glucose and lactose fermented (yellow slant and butt)
K/K or K/NC = no glucose or lactose fermentation
(What are the A/A organisms on KIA?)
E. coli, Klebsiella spp., Enterobacter spp., (and some Citrobacter)
(What are the K/A organisms on KIA?)
Shigella, Salmonella, Serratia, Proteus, Providencia, Morganella, Edwardsiella, Y. enterocolitica and some Citrobacter spp.
How is the TSI agar different than the KIA agar? What does this mean for the K/A KIA reactions, and which 3 organisms rxns will now be A/A on TSI?
TSI looks for glucose, lactose, and also sucrose
Some glucose fermenters/non-lactose fermenters on KIA (K/A) will now be A/A in TSI due to being sucrose fermenters
S. marcescens
Y. entercolitica
P. vulgaris
What enzyme do some organisms possess to make an indole positive reaction?
They have tryptophanase (which breaks down tryptophan into indole)
There are two indole methods: tube test and spot test. What is the reagent for each?
Tube: p-dimethylaminoBENZaldehyde
spot: p-dimethylaminoCINNAmaldehyde
What does the methyl red (MR) and Voges-Proskaur (VP) tests analyze? What are the two pathways?
looks for the way Enterobacteriaceae metabolize pyruvate
two pathways to do this:
- mixed acid pathway
- acetoin / butylene glycol
MR: looks for mixed acid
VP: looks for acetoin
(Enterobacteriaceae are usually pos for one or the other, but not both)
What does the citrate test look for? What does a positive result look like?
If an organism can use citrate as its only source of carbon
Growth and blue-colored slant is pos
(No growth and green slant is neg)
What does lysine iron agar (slant) look for? What do A, K, and R mean? What does H2S look like?
Determines if an enteric decarboxylates or deaminases lysine
A = Acid (yellow)
K = alkaline (purple)
R = deamination (red)
H2S production = black
What are the biochemical results of a LIA slant look like/mean? (K/K, R/A, K/A)
So glucose ferments and turns the butt yellow (acid).
Then if lysine is decarboxylated: the whole tube is alkaline aka purple (K/K)
If lysine is deaminated: only the slant turns red and the butt remains acidic aka yellow (R/A)
If lysine is neither decarboxylated or deaminated, the slant is alkaline and butt is acidic (K/A)
What is looked for in the urease test? Pos and neg colors?
Looks for enzyme urease that is able to turn urea to ammonia
Pos: pink/red color
Neg: yellow
What is a strong urease producer ion Stuart’s urea broth?
Proteus spp.
what does the oxidase test look for, and what two spp. of stool bacteria are oxidase positive?
determines whether an organism possesses the cytochrome c oxidase enzyme
Aeromonas spp.
Campy spp.
