QUE-BACT CHROMO LISTERIA AGAR

Technical Data #1840a / 2013.09.14

QBC Listeria Agar is a solid selective medium used for isolation and cultivation of Listeria monocytogenes from foodstuffs and other materials. On this medium, colonies of Listeria monocytogenes give a blue-green colour with an opaque halo while the others Listeria sp appear as blue-green colonies without any halo. Lithium chloride, nalidixic acid, ceftazidime, cycloheximide and polymyxin B inhibit bacterial or fungus growth.

 


 

FORMULA
in grams per liter purified filtered water

Mixed Peptones

26,0

Yeast Extract

8,0

Sodium Chloride

5,0

Growth Factor

4,2

Lithium Chloride

10,0

Sodium Phosphate, dibasic

2,5

X-Glucoside

0,05

Agar

15,0

Supplement

 

Substrate

40 ml

Antibiotics

 

Nalidixic Acid

0,02

Ceftazidime

0,02

Cycloheximide

0,1

Polymixine B

100 000 units

 

pH 7,2 +/- 0,2 à 25º C

This approximate formula may be adjusted and/or enriched to obtain best results.


PRECAUTIONS
This medium is for laboratory use only.


STORAGE
Store prepared media at 2-8º C protected from direct light. The QBC Kit should be kept in tightly-sealed containers at 2-8º C.


SIGN OF DETERIORATION
Media should not be used if the expiry date has passed. Prepared media should not be used if there are signs of contamination or deterioration (shrinking, cracking, evaporation or discoloration). Do not use dehydrated base if it is caked.


DIRECTIONS
Suspend one bottle of 71,0 g of dehydrated base medium in 950 ml of purified filtered water. Heat with frequent agitation and boil for one minute. Sterilize at 121º C for 15 minutes. Cool to 45-50º C. Add one bottle of supplement and one vial of antibiotics. Mix gently and dispense into sterile Petri dishes.
 


PROCEDURE

Prior to inoculate, the prepared media should be brought to room temperature.

  1. Inoculate the specimens directly onto the plate.
  2. Alternately, enrich the food samples in Demi-Fraser Broth (1:10) and incubate at room temperature for 18-24 hours. Subculture onto QBC Agar and incubate at 35º C for 24 hours.
  3. Examine for Listeria monocytogenes typical colonies : blue-green colonies with an opaque halo. Incubate for an additionnal 24 hours if there is no growth or if growth does not show typical colonies.
  4. Confirm each presumptive colony by a suitable confirmation test.


QUALITY CONTROL

Results after 24 hrs at 35ºC

Organisms

ATCC

Growth

Listeria monocytogenes

15313

+ blue-green, w/ opaque halo

Listeria innocua

33090

+ blue-green, w/o halo

Staphylococcus aureus

25923

-

Escherichia coli

25922

-

Candida albicans

10231

-


LIMITATIONS OF METHOD
This medium is only a part of the identification.
Other tests may be required.


REFERENCES

  1. Fraser and Sperber. 1988 Rapid detection of Listeria spp. in food and environmental samples by esculin hydrolysis. J. Food Prot. 51 :762-765.
  2. Donnelly and Baigent. 1986. Method for flow cytometric detection of Listeria monocytogenes in milk. Appl. Environ. Microbiol. 52 : 689-695
  3. Lee, W.H. and D. McClain, 1986 Improved Listeria monocytogenes Selective Agar. Applied and Environmental Microbiology 52:1215-1217.
  4. Ottaviani, F. Ottaviani, M. Agosti, M. 1997 Differential Agar Medium for Listeria monocytogenes. In ëQuimper froid Symposium proceedingsí P6 ADRIA Quimper (F) 16-18 June 1997
  5. Ottaviani, F. Ottaviani, M. Agosti, M. 1997 Esperienza su un agar selettivo e differenziale per Listeria monocytogenes. Industrie Alimentari 36 : 1-3
  6. Vlaemynck, G., V.Lafargue, S. Scotter 2000 Improvement of Listeria monocytogenes by the application of ALOA, a diagnostic, chromogenic isolation medium. J. Apll. Microbiol., 88 :430


CATALOGUE NUMBERS

QBC Listeria Agar

500g

QB-39-1013

QBC Listeria Agar Kit
Contains Dehydrated base medium, Supplement and Antibiotics to produce1 liter of medium

 

QB-KT-1840

 

 

 

Prepared media

 

 

Plates, 100 x 15 mm

10/pkg

1840

Mono-Plates, 100 x 15 mm

10/pkg

1840M

 

 

 

Others

 

 

Demi-Fraser Broth, Dehydrated powder

500 g

QB-39-1803

Demi-Fraser Broth, 225ml /bottle

10/pkg

5298

 


 

 

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