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FH midterm 1 > Listeria, Salmonella > Flashcards

Listeria, Salmonella Flashcards

1
Q

Listeria monocytogenes

- resistance

A
  • multiplies in soil and water
  • multiplies up to 10% NaCl concentration
  • multiplies til pH 4.4 (more sensitive to organic acids)
  • heat resistance: 0-42C (multiplication); 60C few minutes (destruction)
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2
Q

Listeria monocytogenes

- which media to use

A

Fraser broth, ALOA agar, Oxford agar, Palcam agar

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3
Q

Listeria monocytogenes

- Fraser broth

A
  • liquid medium
  • Inhibitory components: LiCl, nalidixic acid, akriflavine-hidrochloride
  • reaction: olive green, black complex
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4
Q

Listeria monocytogenes

- ALOA

A
  • Solid media
  • ALOA: Agar Listeria Ottavani and Agosti
  • Inhibitors: LiCl, nalidixic acid, ceftazimide, cycloheximide, plymyxin B, L-a-phosphatodyl-inositol
  • reaction: Listeria spp produces blue-green colonies and pathogenic species (L. monocytogenes and L. ivanovii) produce similar color colonies with opaque halo
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5
Q

Listeria monocytogenes

- oxford-agar

A
  • solid media
  • inhibitors: LiCl, nalidixic acid, akriflavine-hidrochoride, aesculin, ammonium-iron(III)-citrate
  • reaction: brownish green colonies with black halo
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6
Q

Listeria monocytogenes

- Palcam agar

A
  • solid media
  • Palcam: Polymyxin-B, Akriflavine, Lithium-chloride, Na-cetazimid, Aesculin, Mannit
  • Inhibitors: Plymyxin-B, Acriflavin, LiCl, Ceftazimide sodium
  • Reaction: greyish green colonies with black halo
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7
Q

Listeria monocytogenes

- conformation test to use

A
  • Catalase test, Motility test, Haemolysis test, CAMP-test, acid production from carbohydrates
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8
Q

Listeria monocytogenes

- Catalase test

A

Listeria monocytogenes is catalase positive (gas formation/bubbles are seen)
- Catalase is an enzyme that mediates the breakdown of hydrogen peroxide (H2O2) into oxygen (O2) and water (H2O)

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9
Q

Listeria monocytogenes

- motility test

A
  • inoculation into a triptone-soy-yeast broth, 25*C for 8-24hr –> typical somersaulting/tumbling motility under microscope
  • deep inoculation into soft agar, 25*C, 8-24hr –> growth in an umbrella form
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10
Q

Listeria monocytogenes

- Haemolysis test

A
  • method: hemolysis on sheep-blood agar, 37*C, 24hr
  • L. monocytogenes: smooth, bright, narrow b-hemolysis
  • L. ivanovii: wide, bright b-hemolysis
  • L. innocua: no hemolysis
  • L. seeligeri: weak b-hemolysis
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11
Q

Listeria monocytogenes

- CAMP test

A
  • CAMP (Christine, atkins, munch, peterson)
  • L. monocytogenes strengthens the hemolysis of Staph. aureus –> strong, arrow-shaped hemolysis
  • L. ivanovii does the same but with Rhodococcus equi
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12
Q

Listeria monocytogenes

- acid production from carbohydrates

A
  • L. monocytogenes can produce acid from rhamnose (positive reaction) –> pH decrease and the color turns yellow
  • cannot produce acid from xylose (negative reaction) –> stays purple
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13
Q

Salmonella enterica

- characteristics

A
  • multiplying: 6-47C, optimum: 35-37C (body temp)

- pH resistance: 3,8-9,5. Optimum pH: 7-7,5

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14
Q

Salmonella enterica

- resistance

A
  • freezing
  • at low water activity
  • 7D values: 60C 2-6min. 70C < 1min. Low water activity - extremely high resistance: 7D value at 70*C: 1050 min
  • 0,1% acetic acid (pH 5.1) can prevent growth
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15
Q

Salmonella enterica

- which media to use for detection

A
  • RVS (Rappaport-Vassiliadis broth), MKTTn, XLD agarm BP agar, BPLS agar, MSRV agar
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16
Q

Salmonella enterica

- RVS: Rappaport-Vassiliadis broth

A
  • Composition: soy peptone, malachite green, magnesium chloride, NaCl, potassium dihydrogen phosphate, pH 5,2+-0.2
  • Blue color when negative
  • light blue/transparent when positive
17
Q

Salmonella enterica

- MKTTn

A
  • MKTTn (Muller-Kauffman, tetrathionate, novobiocin)
  • composition: Na-tiosulphate, cattle bile, brilliant green, lugol solution, CaCO3, Novobiocin, pH: 8.2 +- 0.2
  • Light green color
18
Q

Salmonella enterica

- XLD agar

A
  • XLD (Xylose, lysine, desoxycholate agar)
  • composition: xylose, lactose, sucrose (do not form acid from any of them), L-lysine hydrochloride, sodium thiosulphate, ferric ammonium citrate, sodium desoxycholate
  • original color of the medium is red
  • decompose xylose, lactose, sucrose to acid –> yellow color (NOT salmonella)
  • H2S production –> ferrous sulphide –> black color (salmonella)
  • Lysine –> cadaverine (decarboxylation) –> form purple color/ring around colonies
  • postive: salmonella gives reddish purple colonies (like the medium), sometimes with black center and sometimes a purple ring
19
Q

Salmonella enterica

- MSRV agar

A
  • MSRV agar: Modified Semi-solid Rappaport-Vassiliadis agar
  • composition: soy peptone, malachite green, MgCl, NaCl, potassium dihydrogen phosphate, pH = 5.2 +- 0.2
  • detection is based on ability of Salmonella to move: a growing opalescent zone in the semi liquid media
20
Q

Salmonella enterica

- BPL agar

A
  • BPL (Brillian green, phenol red, lactose)
  • composition: Lactose, protein, NaCl, phenol red, brilliant green, pH= 6.5 +- 0.2
  • original color of medium is red
  • small, purple colonies are formed on the agar because the pH does not increase
21
Q

Salmonella enterica

- BPLS agar

A
  • BPLS (brilliant green, phenol red, lactose, sucrose agar)
  • composition: same as BPL + sucrose
  • purple red colonies are formed
22
Q

Salmonella enterica

- confirmation methods

A
  • Biochemical conformation: TSI agar, Urea medium, tryptone broth, lysine broth, buffered glucose broth, Voges-Proskauer test, Methyl red test, ONPG test
  • Serological examination
23
Q

Salmonella enterica

- TSI slang agar

A

TSI (Triple-sugar-iron agar)
Composition: lactose, sucrose, glucose, iron citrate, sodium thiosulphate
Reaction:
- the original color of medium is orange
- fermentation of glucose: yellow color at the bottom of the tube: acid production + (with or without gas) –> glucoe positive
- fermentation of lactose: - (but! Salmonella enterica subzp. arizonae +/-) –> TSI top: red –> lactose and sugrose negative
- H2S production (from Na-thiosulphate): + black color (black spots in the sample)

24
Q

Salmonella enterica

- decomposition of urea (urease test)

A
  • Salmonella is urea negative, cannot produce ammonia from urea, the sample will not turn purple
  • original color of the medium is orange/yellow
  • Positive reaction: turns pink then purple (e.g Proteus)
  • negative reaction: stays yellow (salmonella)
25
Q

Salmonella enterica

- tryptone broth (indol production)

A
  • Composition: casein peptone, NaCl, distilled water
  • salmonella is indole negative
  • positive test: purple ring (rosindole) at the top of the tube
  • negative test: yellow ring at the top of the tube
26
Q

Salmonella enterica

- Lysine decarboxylation/lysine broth

A
  • salmonella is positive for it
  • composition: lysine, tryptone, meat extract, glucose, pyridoxal hydrochloride, paraffin oil, cresol red, bromocresol purple
  • negative reaction: the microbe produces acid ant the color of the broth turns to yellow (Citrobacter)
  • positive reaction: alkaline pH, cloudiness and the original purple color can be seen (Salmonella, Klebsiella)
27
Q

Salmonella enterica

- Voges-Proskauer test

A
  • negative for salmonella, positive for klebsiella
  • negative reaction: remains the original color
  • positive reaction: 2 hours later it becomes pink
28
Q

Salmonella enterica

- ONPG test

A
  • salmonella is ONPG negative
  • negative reaction: no change in color
  • positive reaction: yellow color
  • Salmonella enterica subsp. arizonae is ONPG +!
29
Q

Salmonella enterica

- serological confirmation

A
  • antibodies (prepared agianst specific antigens found on the cell wall and flagella) are used in the Salmonella Isolate
  • 1st step: exclude self-agglutination (if + not appropriate for serological determination!)
  • O antigen: somatic Ag
  • Vi antigen: surface (envelope) antigen
  • H antigen: flagella

FH midterm 1 (3 decks)

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