BIOCHEMICAL TESTS FOR IDENTIFICATION OF ENTEROBACTERIACEAE Flashcards
memorization
Good test to differentiate Enterobacteriaceae from non-fermenters
Cytochrome oxidase test
Cytochrome oxidase positive result:
Maroon-violet color within 30 seconds
Enumerate cytochrome oxidase-positive organisms:
- Campylobacter
- Aeromonas
- Neisseria
- Pseudomonas
- Pasteurella
Mnemonic: “CAN PP”
Positive result in Nitrate reduction test:
Red, or no color after addition of zinc dust
Positive result in Carbohydrate Fermentation test:
With phenol red indicator, change from RED to YELLOW.
A test for slow lactose fermentation (late). Helpful in differentiating Citrobacter (+) from most Salmonella (-)
ONPG test
Positive result in ONPG:
Yellow color
Enzymes present in rapid lactose fermenters:
B-galactosidase
Permease
Enzymes present in late lactose fermenters:
B-galactosidase only
Non-lactose fermenters does not possess B-galactosidase and Permease
Good test to differentiate Salmonella from Shigella:
H2S production test
H2S production test positive result:
Black precipitate
Ratio of sugars present in Triple Sugar Iron (TSI) Agar:”
Glu : Lac: Suc
1:10:10
Growth in the slant is _____ (Aerobic/Anaerobic)
Slant = Aerobic
Growth in the Butt is _____ (Aerobic/Anaerobic)
Butt = Anaerobic
In Butt/Slant (TSI), fermentation happens in:
Butt
In TSI Agar
Yellow =
Pink =
Pink Butt =
Yellow Butt =
Yellow = Acid (A)
Pink = Alkaline (K)
Pink Butt = glucose not fermented
Yellow Butt = glucose fermented
In TSI
If only glucose were fermented, the TSI result is:
Glucose only = K/A (Pink/Yellow) or (Alkaline/Acid)
In TSI
If glucose and another sugar (lactose/sucrose) were fermented, the TSI result is:
Glucose + Lactose/Sucrose = A/A (Yellow/Yellow) or (Acid/Acid)
In TSI
Non-fermenters TSI result would be:
Non-fermenters = K/K (Pink/Pink) or (Alkaline/Alkaline)
Difference between Proteus vulgaris and Proteus mirabilis:
Proteus vulgaris = Sucrose fermenter (A/A)
Proteus mirabilis = Non-sucrose fermenter (K/A)
Citrobacter TSI:
K/A or A/A
Citrobacter is a Late-Lactose-Fermenter. Initially, it’s TSI is K/A . In prolonged incubation, it’s TSI will turn into A/A
Salmonella and Shigella TSI:
Salmonella & Shigella = K/A
Salmonella = K/A with black precipitate (H2S +)
Shigella = K/A; no black precipitate
one way to differentiate Salmonella and Shigella is the H2S production test;
Salmonella (H2S+)
Shigella (H2S-)
Indole positive organisms:
- Escherichia coli
- P. vulgaris
- Klebsiella oxytoca
Klebsiella oxytoca is the ONLY Indole(+) Klebsiella
another way to differentiate P. vulgaris and P. mirabilis: P. vulgaris is indole (+) while P. mirabilis is indole (-)
P. vulgaris = A/A; indole (+)
P. mirabilis = K/A; indole (-)
Enzyme that is produced in indole test:
Tryptophanase
Test to diffrentiate lactose-fermenting Enterobacteriaceae:
Methyl-Red - Vogues Proskauer
Test for the identification of lactose-fermenting Enterobacteriaceae:
Citrate
Positive result in Citrate test:
Growth with an intense BLUE COLOR on the slant.
E. coli IMVIC reaction:
E. coli = (+) (+) (-) (-)
K. pneumoniae IMVIC reaction:
K. pneumoniae = (-) (-) (+) (+)
E. aerogenes & E. cloacae IMVIC reaction:
E. aerogenes & E. cloacae = (-) (-) (+) (+)
K. oxytoca IMVIC reaction:
K. oxytoca = (+) (-) (+) (+)
K. ozanae IMVIC reaction:
K. ozanae = (-) (+) (-) (-)
E. agglomerans IMVIC reaction:
E. agglomerans = (-) (-) (-) (-)
Rapid Urease Producers:
Proteus
Morganella
Positive result in Urease test:
Yellow to PINK
Urease-positive organisms:
- Proteus
- Providencia rettgeri
- Morganella
- Cryptococcus (Fungi)
- H. pylori
- Ureaplasma
- Nocardia
- Klebsiella
- S. epidermidis
- S. saprophyticus
mnemonic: “PP Mo CHUNKSS”
Phenylalanine deaminase (PD) positive result:
GREEN COLOR after the addition of ferric chloride
PD-positive organisms:
- Proteus
- Providencia
- Morganella
- Klebsiella (SLOW)
mnemonic: “PD PP Mo, K?” / “PD PP Mo GREEN, K?”
Decarboxylase reaction positive result:
yellow to PURPLE
In Decarboxylase reactions
Klebsiella =
Enterobacter =
Klebsiella = LDC (+) (Lysine Decarboxylase)
Enterobacter = ODC (+) (Ornithine Decarboxylase)
Motility of bacteria is determined using a ______ media
motility: SEMISOLID media
Non-motile Enterobacteriaceae:
- Shigella
- Klebsiella
- Yersinia enterocolitica (Non-motile @37C) (Motile @ 22C)
Mnemonic: “SKY”
This test is used to determine the ability of an organism to use acetamide as the sole source of carbon
Acetamide Utilization Test
Organism positive for Acetamide utilization test:
Pseudomonas aeruginosa (+)
Positive result of acetamide utilization test:
BLUE COLOR
This test is used to determine if an organism can use acetate as the sole source of carbon:
Acetate utilization test
Positive result of acetate utilization test:
BLUE COLOR
Organism positive for acetate utilization test:
E. coli (+)
H2S positive organisms:
- Proteus
- Edwardsiella
- Citrobacter
- Salmonella
Mnemonic: “PECS”
VP positive organisms:
- Klebsiella
- Enterobacter
- Serratia
- Hafnia
Mnemonic: “KESH”
Lactose-Fermenter organisms:
- Escherichia
- Klebsiella
- Enterobacter
Mnemonic: “EKE”
Late-Lactose-Fermenter organisms:
- Citrobacter
- Salmonella arizona
- Shigella sonnei
- Serratia
- Hafnia
- Yersinia
Mnemonic: “CSSSHY”
Non-Lactose Fermenter organisms:
- Proteus
- Providencia
- Morganella
- Salmonella
- Erwinia
- Shigella
- Edwardsiella
Mnemonic: “PP Mo SESE”
