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What are the sources of fecal contamination?
water source stars at mountain picks to revers that mixed with washes. All of these sources are exposed to human/animal fecal contamination and other pollutants.
- All enterobacterceaeAll ferment lactose
- All gram negative rods
- All anaerobe facultatives
- All produce gas
What does coliforms and non-coliforms of fecal contamination have in common?
- They all cause GI tract infections
- diarrhea, dysentery, and vomiting.
Why the media we used in lab 8 is selective media
Because it inhibit the growth of gram positive bacteria and select the growth of gram negative
Why is the media we used in lab 8 is deferential media
It differentiate between lactose fermenting coliforms from other gram negative that do not ferment lactose.
Water screening test
- A quick test of coliforms in 100 mL of water.
- The water will change color blue/green and participials will glow under 360 nm UV light if coliforms are present
Why is Eosin methylene blue (EMB) is a deferential media?
Lactose frequenters produce acid:
- E. coli produce a lot of acid turn media color green shean
- Other lactose fermenters produce less acid turn the media pink to red/purple
Why is Eosin methylene blue (EMB) is a selective media?
- Because it selects gram negative growth only
- Some dyes in this media inhibit gram +
EHA Media (Hektoen Enteric agar)
- Selective: Contains bile salt that inhibits G+
- E. coli turn agar color to pink, yellow or orange
- Shigella: blue green
- Salmonella produce H2S black
MCA (MacConkey agar)
- Selective: Bile salt & crystal violet inhibit G+
- Lactose frementer turn media pink.
Define and list characteristics of coliforms. Why is water tested for coliforms?
- Members of enterobactriaceae, facultative anaerobes, produce gas, ferment lactose.
- Because they can cause GI tract infections
Name three diseases spread through water.
Dysentery, diarrhea, and vomiting, cholera
- Grow form: cluster
- Colony color: Golden yellow
- Catalase test: positive
- Infection: MRSA (Methicillin resistance staphylococcus aureus)
- Growth form: Chains
- Colony color: white
- Catalase test: negative
- Infection: VRE (vancomycin resistance enterococcus)
Enzyme produced by Staphylococcus that break down oxygen radicals
Staphylococcus in general
- normal residents of the body
- opportunists can become pathogenic under certain conditions
Mannitol salt plate
Mannitol is used as sugar
- Differential media : Because it will turn yellow if mannitol is fermented (S. saprophyticus & S. aureus)
- Selective media: because it selects for only halotolorant bacteria
What are S aureus, S. saprophyticus and S. epidermis have in common?
What differentiate between them?
- All are halotolorant
- S. epidermis; cause (endocarditis inflammation of the heart lining), Cannot ferment mannitol
- S. saprophyticus cause UT infection,
- S, aureus: cause MRSA,
(BAP) Blood agar plate
- S.epidermis: gamma hemolysis (non hemolysis)
- S. saprophyticus : gamma hemolysis
- S. aureus: Beta hemolysis (complete hemolysis)
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