media and reagents Flashcards
TSI ingredients
Triple sugar iron slant: glucose, lactose sucrose, sodium thiosulfate, peptone. phenol red is pH indicator
TSI K/A H2S+ gas+ biochemical reaction indicates
K=glucose fermentation (occurs rapidly) turning slant yellow. Organism catabolizes aa producing NH3 making slant alkaline and red. Alkalinity will not overcome butt which remains yellow.
A=only glucose fermented
H2S thiosulfate reduced to H2S
3 infamous lactose fermenting organisms
E. coli, K. pneumoniae, Enterobacter aerogenes
3 common non lactose fermenting enterics
Salmonella, Shigella, Citrobacter, Proteus
TSI A/A gas
A/A=glucose and lactose fermenter. Gas is a result of fermentation.
TSI K/K
peptones catabolized aerobically and anaerobically.
MIO:Motility indole ornithine
Motility: turbidity
Indole: James reagent (dimethylaminobenzealdehyde in HCl and amyl alcohol-alchohol concentrates color as ring at surface) detect indole (reacts with aldehyde to form red/pink) , a byproduct of tryptophan methabolism
Ornithine: ornithine decarboxylation – formation of a highly alkaline product, over-neutralizing the acid produced from glucose fermentation in bottom 3/4 of tube see faded purple.
LIA: Lysine Iron Agar describe biochemical reaction
Ingredients: peptone, yeast, glucose, lysine bromcresol purple, thiosulfate
Lysine: lysine decarboxylation requires an anaerobic env & results in purple butt. deamination of lysine in slant results in redish color.
Iron: thiosulfate in electron receptor and if reduced becomes hydrogen sulfide.
citrate
determines ability to use citrate as sole carbon source brought about by the enzyme citrase. AMmonium ion in sole nitrogen souce. Bromthymol blue is pH indicator. pH>7.6, BMB turns blue. Citrate utilization is an aerobic process, as Na2 CO3 accumulates and is an aerobic compound, the media is basic and truns BMB Prussian blue..
enteric screen biochemicals
citrate, LIA, TSI, urea, MIO
Urea test media
determines organisms ability to hydrolyze urea with urease. it contains phenol red, yellow,8.4 and red>8.4. Determines ability to convert urea to ammonia which is alkaline, raises pH and turns phenol red yellow to pink.
urea test media useful in differentiating microbial causes of which pathogens
UTI pathogens from genus proteus and other enteric bacteria by rapid urease activity.
3 organisms with rapid urease activity
proteus, morganella, providencia
organisms with delayed urease positive organism
citrobacter, enterobacter, klebsiella. pink color in slant only indicateds delayed urease positive organism.
imvic tests
four reactions to identify enterobacteriaceae: indole, methyl red, voges proskauer, citrate (I for rhymying)
methyl red test in imvic reaction
detects an organisms ability to detect and maintain stable acid end products from glucose fermentation. methyl red is a ph indicator and is red at a ph of 4.4 or less. when added to broth with e. coli it turns red
VP in IMViC tests
detects butylene glycol producers. KOH added to broth containing acetoin producinmg diacetyl which reacts with guanidine components of peptone to react with alpha-naphthol to produce red color. alpha is a catalyst and color intensifier
citrate
detects organisms ability utilitize citrate as sole source of carbon. pH indicator is bromothymole blue. production of oxaloacetate and acetate as byproducts of citrate utilization results in alkaline pH changing media from blue to green
positive and negative controls for IMViC tests
E. coli positive for I & , MR but negative for VP and citrate. K. pneumonia negative: indole, MR, but pos VP and citrate
