1What does HEA stand for?
Hektoen enteric agar
2What type of agar is Hektoen enteric agar?
*selective and differential agar (contains indicators for lactose fermentation and hydrogen sulfide production)
*contains inhibitors to prevent gorwth of gram positive bacteria
*contains peptone (carbon source)
3Why is HEA used?
*used to recover salmonella and shigella from patient specimens
4What sources of sugar are within HEA?
*lactose, sucrose, salicin
5When does the HEA media turn yellowed? Why?
*Bacteria other than shigella and salmonella will acidy the medium (because they use the sugars instead of peptone) turning it yellowed
6Why does HEA media turn blue?
*peptone metabolism (carbon source) by Shigella and Salmonella alkalises the medium (turning it blue)
7What component in HEA media produces black precipitate, when does this happen?
*thiosulfate or ferric ammonium citrate
*when there is H2S present
8What does Shigella look like on HEA media? why?
Shigella colonies looks green because it does not produce H2S (doesn't react with Thiosulfate or ammonium citrate to produce black precipitate)
9What does Salmonella look like on HEA media? Why?
Salmonella colonies look black (they produce hydrogen sulfide in response to the thiosulfate or ferric ammonium citrate in the HEA media)
10What sulfur-reducing bacteria do you need to know? Where can it be found?
*Salmonella, found in intestines
11What is a catalase test? What does pos mean? neg?
Detects the presence of the catalase enzyme
*positive (has catalase-presence of bubbles)
*negative (no catalase-non bubbles)
12What does catalase enzyme do to H2O2?
*splits H2O2 into oxygen and water
13Catalase test rx for Staphylococus genus?
Positive catalase rx
14Catalase test rx for Streptococcus genus?
Negative catalase rx
15Briefly describe genus of Staphylococcus genus:
*gram positive
*non-spore forming cocci