Differential again

1
Differential again!

• 5-17 5-18 5-19 5-20

2
FROM LAST WEEK

• Dont forget that yellow in the sugar tubes
  (phenol red sucrose and dextrose) was positive
  for fermentation, they produced acid and a gas
  bubble in the Durham tube was CO2
• ALSO the nitrate broths were red if positive for
  nitrate reduction, BUT red after ZINC was
  negative for nitrate reduction. What chemicals
  were added initially for results?
• MR/VP-both tubes turned red if positive. What
  chemicals were added? Look it up!

3
Also from last week.

• Citrate test (ex. 5-7). IF the bacteria can use
  citrate as its sole carbon source the tube will
  turn Prussian blue. (this is an alkaline
  reaction)
• Starch hydrolysis (ex. 5-11). Youll add iodine
  to the plates and look for clearing around the
  bacterial growth. If it is clear, it is positive
  for starch hydrolysis.
• Urea broth- (ex. 5-12). The bacteria may produce
  an enzyme called urease which breaks down urea.
  IF this is present, an alkaline reaction occurs
  and the broth turns pink.

4
NEW

• SIM (sulfide, indole, motility) ex. 5-17
• after inoculation, youll look for a black
  precipitate indicating sulfur reduction.
• You will also add Kovacs reagent after
  incubation and look for a red ring on top of the
  culture, indicating the presence of INDOLE.
• Kliger Iron Agar (ex. 5-18)-determines ability to
  ferment glucose, lactose, and reduce sulfur. See
  figure 5-59 for possible results after incubation

5
Bacitracin Susceptibility Test ex. 5-19

• Place bacitracin disc on a thoroughly inoculated
  plate and incubate
• A 10 mm or greater zone of inhibition may form
  around the disc, indicating that bacteria were
  susceptible to the antibiotic

6
Blood Agar (ex. 5-20)

• 3 major types of hemolysis are gamma or non
  hemolytic (no change), alpha hemolytic (partial
  use), and beta hemolytic (completely used the
  blood)
• Inoculate plate thoroughly then incubate. Next
  week read the results to determine which type of
  hemolysis your cultures have.