skills 11 Flashcards
selective property
only certain bacteria can grow
differential property
metabolic differences between the bacteria are easily seen
MacConkey agar test
{purpose}
- tests water for presence of coliforms (gram negative, lactose fermentation)
- selective ingredients (crystal violet & bile salts) interfere w/ growth of gram-positive bacteria
MacConkey agar test results
- positive= pink/red color to media/bacteria
- negative= tan/colorless to media/bacteria
MacConkey agar test products
gram-negative rods; enteric (intestinal tract) bacilli
MacConkey agar test media
MacConkey agar; pH indicator dye (neutral red) {indicates if bacteria ferments lactose to an acid}
Eosin Methylene Blue (EMB) agar test
{purpose}
- tests water for presence of coliforms (gram negative , lactose fermentation)
- selective ingredients (eosin & methylene blue) interfere w/ growth of gram-positive bacteria
Eosin Methylene Blue (EMB) agar test results
- positive= very dark and/or metallic green sheen color to colonies (especially E. coli); sometimes fisheye colonies appear; darker purple center w/ lighter pink outer area (Enterobacter)
- negative= bacteria are the color of the media & appear to blend in w/ the media; bacteria / media are the wrong color
Eosin Methylene Blue (EMB) agar test products
gram negative bacteria that ferment lactose
Eosin Methylene Blue (EMB) agar test media
eosin methylene blue agar = eosin + methylene blue
Mannitol salt agar (MSA) test
{purpose}
- used to isolate and identify Staphylococcus aureus
- detection of coagulase positive staphylococci
Mannitol salt agar (MSA) test results
- positive= media is yellow
- negative= media remains pink in color
Mannitol salt agar (MSA) test products
fermented mannitol
Mannitol salt agar (MSA) test media
sodium chloride; mannitol; phenol red pH indicator
what are the selective and differential ingredients of MSA?
- selective= salt
- differential= mannitol (ability to ferment it)
