Laboratory Diagnosis of Enterobacteriaceae Flashcards
identify
- BAP: shiny, opaque, smooth, nonhemolytic
- MAC: NLF/LF
Plesiomonas shigelloides
identify
produces flat colonies with jagged edges on MAC
Shigella sonnei
identify
TSI contains 10 parts (?) : 10 parts (?) : 1 part (?) and (?)
- lactose
- sucrose
- glucose
- peptone
identify
This test is used to determine the ability of an organism to utilize sodium citrate as its only carbon source and inorganic ammonium salts as its only nitrogen source
citrate utilization
identify
- MAC: NLF
- HE: colorless
- XLD: red or yellow
Hafnia alvei
identify
Christensen’s citrate medium incorporates phenol red (as the Ph indicator) and organic nitrogen.
At an alkaline pH, the indicator turns from yellow to (?)
citrate utilization
pink
identify
- Production of hydrogen sulfide (H2S)
- Salmonella spp. appear as brown to black precipitate
isolation of Salmonella spp. & Shigella spp.
Bismuth sulfite agar
identify
- H2S (TSI agar): (-)
- urease: (-)
- indole: (+/-)
- methyl red: (+)
- voges-proskauer: (-)
- citrate (simmons): (-)
- KCN: (-)
- phenylalanine deaminase: (-)
- mucate: (d)
- mannitol: (+/-)
Escherichieae
identify
- Shigella spp. appear colorless
- Salmonella spp. colorless with a black center
isolation of Salmonella spp. & Shigella spp.
Salmonella-Shigella agar (SS)
identify
used to differentiate sorbitolnegative E. coli O157:H7 from other strains of E. coli
MacConkeysorbitol agar (MAC-SOR)
identify
reagents
rapid spot indole test
- kovac’s reagent
- p-dimethylaminobenzaldehyde Bio Merieux (or equivalent)
identify
This test is helpful in initial differentiation of Proteus, Morganella, and Providencia organisms, which are positive
phenylalanine deaminase (PAD)
identify
may be red pigmented, especially if plate is left at 25°C on MAC
Serratia marcescens
identify
Bacteria that can grow on this medium turn the bromthymol blue indicator from green to (?)
citrate utilization
blue
identify
methyl red test positive:
(?) color at surface of the medium
MR-VP medium/MR-VP broth
red
identify
- H2S (TSI agar): (-)
- urease: (-/+)
- indole: (-)
- methyl red: (-)
- voges-proskauer: (+)
- citrate (simmons): (+)
- KCN: (+)
- phenylalanine deaminase: (-)
- mucate: (+/-)
- mannitol: (+)
Klebsielleae
identify
Rapid development of a (?) color on the filter paper, usually within 30 seconds, is indicative of a positive test result.
rapid spot indole test
bright pink-red
identify
(?) medium is an alternative test medium
citrate utilization
Christensen’s citrate
identify
- MAC: NLF
- HE: green, H2S production
- XLD: red with H2S
Salmonella spp.
identify
colonies on SBA are pinpoint at 24 hours but exhibit a rough, cauliflower appearance at 48 hours
Y. pestis
identify
- safety pin appearance
- bipolar appearnce
Yersinia spp
identify
- H2S (TSI agar): (-)
- urease: (+)
- indole: (+/-)
- methyl red: (+)
- voges-proskauer: (-)
- citrate (simmons): (-)
- KCN: (-)
- phenylalanine deaminase: (-)
- mucate: (none)
- mannitol: (+)
Yersiniae
identify
Simmons Citrate Agar contains (?)
ammonium dihydrogen phosphate
identify
methyl red test negative:
(?) color at surface of the medium
MR-VP medium/MR-VP broth
yellow
identify
negative
voges-proskauer test|results
Escherichia coli
identify
- MAC: NLF
- HE: green
- XLD: colorless
Shigella spp.
identify
K/NC
(glucose, lactose, and sucrose non utilizer)
TSI agar|results
Pseudomonas aeruginosa
identify
- MAC: most LF, some NLF, generally flat, dry, pink colonies with a surrounding darker pink area of precipitated bile salts
- HE: yellow
- XLD: yellow
Escherichia spp.
identify
A (?) color denotes a negative indole test after addition of Kovacs Reagent
SIM (sulfide, indole, motility) medium|results
yellow
identify
- H2S (TSI agar): (+/-)
- urease: (+/-)
- indole: (+/-)
- methyl red: (+)
- voges-proskauer: (-)
- citrate (simmons): (d)
- KCN: (+)
- phenylalanine deaminase: (+)
- mucate: (-)
- mannitol: (-/+)
Proteeae
identify
Decarboxylates or deaminates lysine and forms hydrogen sulfide (H2S)
lysin iron agar
identify
used as the positive control
rapid spot indole test|quality control
E. coli ATCC 25922
identify
A negative reaction is evidenced by no growth or growth with the medium remaining (?) in color
simmons citrate agar
green
identify
A positive test for indole is denoted when a (?) color band is formed at the top of the medium after addition of Kovacs Reagent
SIM (sulfide, indole, motility) medium|results
pink to red
identify
The production of (?) color indicates that indole has been produced from the amino acid tryptophan
kovac’s indole test
red
identify
R/A
(lysine deamination and glucose fermentation)
Proteus vulgaris
identify
- H2S (TSI agar): (+)
- urease: (-)
- indole: (+)
- methyl red: (+)
- voges-proskauer: (-)
- citrate (simmons): (-)
- KCN: (-)
- phenylalanine deaminase: (-)
- mucate: (-)
- mannitol: (-)
Edwardsielleae
identify
- Salmonella spp. colorless to red with black center
- Shigella spp. colorless to red
- Other Enterobacteriaceae Yellow
isolation of Salmonella spp. & Shigella spp.
Xylose-lysine-deoxycholate agar (XLD)
identify
a selective medium specifically used for the isolation of Y. enterocolitica
Cefsulodin-irgasan-novobiocin agar (CIN)
identify
Cultures to be tested must be grown on media containing tryptophan.
Trypticase soy agar (TSA) with or without sheep red blood cells is suitable
rapid slot indole test
identify
K/A
(glucose fermentation)
lysin iron agar|result
Shigella flexneri
identify
reagents
nitrate reduction test
solution A
* sulfanilic acid
* acetic acid
solution B
* β-Naphthylamine
* acetic acid
* glacial acetic acid
* distilled water
identify
voges-proskauer test:
A positive reaction is indicated by the development of a distinct (?) color which occurs within 5 minutes
MR-VP medium/MR-VP broth
red
identify
positive
(Change in color of slant from light orange to magenta)
urea hydrolysis|results
Proteus vulgaris
identify
positive
voges-proskauer test|results
Enterobacter cloacae
identify
N,N-dimethyl-α-naphthylamine and sulfanilic acid is added
(?) color indicates the presence of nitrite
nitrate and nitrite reduction
red
identify
indole negative
kovac’s indole test|results
Pneumoniae
identify
Salmonella spp. appear as white to pink or red colonies surrounded by a bright halo
isolation of Salmonella spp. & Shigella spp.
brilliant green agar
identify
- MAC: NLF, may swarm, foul smell
- HE: colorless
- XLD: yellow or colorless, with/without H2S
Proteus spp.
identify
- Gram negative bacilli
- Coccobacilli or straight rods with rounded ends
enterobacteriaceae
identify
A negative motility test is indicated by growth confined to the (?)
SIM (sulfide, indole, motility) medium|results
stab line
identify
Cloudiness spreading from the inoculation line is positive for (?)
sulfide-indole-motility agar
motility
identify
Wright or Giemsa stain of lesions infected with (?):
DONOVAN Body are blue rod with prominent polar granules, giving rise to the safety-pin appearance, surrounded by a large, pink capsule.
Klebsiella granulomatis
identify
A positive motility test is indicated by a (?) flaring from the line of inoculation
SIM (sulfide, indole, motility) medium|results
diffuse zone of growth
identify
Urea Agar contains (?) and (?) as the pH indicator
- urea
- phenol red
identify
may be used as enrichment for the isolation of Shigella
- Gram-negative broth (GN)
- Selenite broth (SEL)
identify
- MAC: LF, mucoid
- HE: yellow
- XLD: yellow
Klebsiella spp.
identify
- MAC: NLF
- HE: colorless
- XLD: yellow or colorless
Providencia spp.
identify
A positive H2S test is denoted by a (?) of the medium along the line of inoculation.
SIM (sulfide, indole, motility) medium|results
blackening
identify
- H2S (TSI agar): (+/-)
- urease: (+/-)
- indole: (-/+)
- methyl red: (+)
- voges-proskauer: (-)
- citrate (simmons): (+)
- KCN: (+/-)
- phenylalanine deaminase: (-)
- mucate: (none)
- mannitol: (+)
Citrobacteriaceae
identify
positive
methyl red test|results
Escherichia coli
identify
selective agars in addition to SBA, chocolate, and MacConkey agars
- Hektoen enteric agar (HE)
- xylose-lysine-deoxycholate agar (XLD)
- Salmonella-Shigella agar (SS)
identify
negative
[No color change (agar slant and butt remain light
orange)]
urea hydrolysis
Escherichia coli
identify
This test is used to determine the ability of an organism to produce the enzyme urease, which hydrolyzes urea
urea hydrolysis (Christensen’s method)
identify
- MAC: NLF, may be colorless to peach
- HE: salmon
- XLD: yellow or colorless
Yersinia spp.
identify
indole positive
kovac’s indole test|results
Escherichia coli
identify
A positive reaction is indicated by growth with development of a (?) color reaction within the medium
simmons citrate agar
deep blue
identify
culture medias:
- SBA
- Chocolate agar
- MacConkey agar
identify
Broth cultures of Y. pestis exhibit a characteristic ”(?)” in which clumps of cells adhere to one side of the tube
stalactite pattern
identify
The production of H2S is indicated by a black precipitate, and a pink to red color after the addition of Kovac’s reagent is positive for (?)
sulfide-indole-motility agar
indole
identify
The (?) is more sensitive than Kovac’s reagent and is preferred with nonfermentative bacteria
indole production
Ehrlich method
identify
Selective enrichment for the growth of Salmonella spp.
isolation of Salmonella spp. & Shigella spp.
Selenite broth
identify
Organisms capable of hydrolyzing urea form ammonia as a byproduct, thus turning the medium alkaline.
The pH indicator turns from pale yellow to (?) in color in these conditions
urea agar slant
pink-red
identify
A (?) color develops if the test result is positive for nitrate reduction
nitrate reduction test|results
red
identify
A/A
(glucose, sucrose, and/or lactose fermenter)
TSI agar|results
Escherichia coli
identify
A negative H2S test is denoted by the absence of (?)
SIM (sulfide, indole, motility) medium|results
blackening
identify
used as the negative control
rapid spot indole test|quality control
Pseudomonas aeruginosa ATCC 27853
identify
- MAC: late LF,
- HE: colorless
- XLD: yellow or colorless
Serratia spp.
identify
(?) are blue rod with prominent polar granules, giving rise to the safety-pin appearance, surrounded by a large, pink capsule
DONOVAN body
identify
Media that are highly selective for the isolation of Salmonella spp.
- CHROM agar Salmonella
- brilliant green agar
- bismuth sulfite agar
identify
reagents
kovac’s indole test
- Amyl/isoamyl alcohol
- p-Dimethylaminobenzaldehyde
- Hydrochloric acid
identify
Approximately 5 drops of Kovac’s reagent is added directly to the broth culture.
The tube is shaken, and if indole is present, a (?) color develops
sulfide-indole-motility agar
red
identify
K/K H2S+
(lysine decarboxylation and no fermentation of glucose, black precipitate in the butt)
lysin iron agar|results
Salmonella typhimurium
identify
No color change indicates a (?) test result
rapid spot indole test
negative
identify
one of the degradation products of the amino acid tryptophan
sulfide-indole-motility agar
indole
identify
negative
(absence of growth)
citrate utilization|results
Escherichia coli
identify
- MAC: LF, may be mucoid
- HE: yellow
- XLD: yellow
Enterobacter spp.
identify
Lactose fermenter, forms blueblack with a metallic green sheen
E. coli
identify
Hydrolysis of urea produces ammonia and CO2
The formation of ammonia alkalinizes the medium, and the pH shift is detected by the color change of phenol red from (?) at pH 6.8 to (?) at pH 8.1
urea hydrolysis
- light orange
- magenta
identify
(?) and (?) serve as indicators of acidification and H2S formation, respectively
TSI agar
- phenol red
- ferrous sulfate
identify
negative
methyl red test|results
Enterobacter cloacea
identify
Bromothymol Blue is (?) at pH (<7.0)
and (?) at pH (>7.6)
citrate utilization
- green
- blue
identify
- MAC: NLF
- HE: colorless
- XLD: red or colorless
Morganella spp.
identify
- MAC: late LF (after 48 hr), colonies are light pink
- HE: colorless
- XLD: red, yellow, or colorless, with/without H2S
Citrobacter spp.
identify
K/A H2S+
(glucose fermentation only, black precipitate in the butt)
TSI agar|results
Salmonella typhi
identify
- MAC: NLF
- HE: colorless
- XLD: red, yellow, colorless, with/without H2S
Edwardsiella spp.
identify
stained with Wayson stain or Methylene Blue stain
Yersinia spp.
identify
After incubation, α-naphthol is added first as a catalyst or color intensifier. Next, 40% potassium hydroxide (KOH) or sodium hydroxide (NaOH) is added, and the tube is gently shaken to increase oxygenation.
Under these conditions, acetoin is oxidized to diacetyl. Diacetyl in the presence of KOH and α-naphthol forms a (?) complex.
voges-proskauer test
red
identify
After incubation, approximately half the broth is transferred to a clean dry tube for the VP test
A (?) color develops after addition of the pH indicator MR
MR-negative cultures remain (?) after addition of the pH indicator (pH 6.0)
methyl red test
- red
- yellow
identify
A rapid indole test using p-dimethylaminocinnamaldehyde:
bacterial colonies are smeared onto filter paper that has been moistened with p-dimethylaminocinnamaldehyde.
The formation of a (?) color within 2 minutes is a positive reaction
indole production
blue green
identify
positive
(Growth on the medium, with or without a change in the color of the indicator. Growth usually results in the bromthymol blue indicator, turning from green to blue)
citrate utilization|results
Klebsiella pneumoniae
identify
- H2S (TSI agar): (+)
- urease: (-)
- indole: (-)
- methyl red: (+)
- voges-proskauer: (-)
- citrate (simmons): (+)
- KCN: (-)
- phenylalanine deaminase: (-)
- mucate: (d)
- mannitol: (+)
Salmonelleae
identify
No color production is a (?) test result and should be confirmed by the addition of zinc dust.
If unreduced nitrate is present, a (?) color develops, confirming the negative test result.
If no color change occurs, a complete reduction has occurred, and the test result is (?)
nitrate reduction test|results
- negative
- red
- positive