Primary Listeria Agar

KM0058 Primary Listeria Agar is a selective medium for the isolation, enumeration and presumptive identification of Listeria species and L. monocytogenes from food and environmental samples.

Listeria monocytogenes is commonly found in soil, sewage, and faeces. It is difficult to eradicate, and can cause serious food poisoning; therefore, L. monocytogenes is frequently tested for in food processing facilities to avoid contamination. Contamination can occur at all steps of the food manufacturing chain from raw materials to point of consumption.

Primary Listeria Agar is used for the detection and presumptive identification of Listeria spp. and the specific differentiation of L. monocytogenes. Based on the method of Ottaviani et al ^{(1 2)}, this medium allows detection and enumeration of Listeria spp. as early as 24 hours. Primary Listeria Agar is recommended by ISO 11290-1:2017 ⁽³⁾ and ISO 11290-2:2017 ⁽⁴⁾ and tested in accordance with ISO 11133:2014 ⁽⁵⁾.

References:

Ottaviani, F., Ottaviani, M., and Agosti M. (1997) Differential agar medium for Listeria monocytogenes. Quimper Froid Symposium Proceedings, P6 ADRIA Quimper, France, 16-18 June.
Ottaviani, F., Ottaviani, M.G., and Agosti, M. (1997). Esperienze su un agar selettivo e differenziale per Listeria monocytogenes. Industrie Alimentari, 36: 888-889.
International Organization for Standardization (2017) 11290-1:2017 Microbiology of the food chain – Horizontal method for the detection and enumeration of Listeria monocytogenes and of Listeria spp. – Part 1: Detection method. Geneva, ISO.
International Organization for Standardization (2017) 11290-2:2017 Microbiology of the food chain – Horizontal method for the detection and enumeration of Listeria monocytogenes and of Listeria spp. – Part 2: Enumeration method. Geneva, ISO.
International Organization for Standardization (2014) 11133:2014 Microbiology of food, animal feed and water – Preparation, production, storage and performance testing of culture media. Geneva, ISO.

Related supplements: BM8050 Primary Listeria Diagnostic Supplement, LS0210 Primary Listeria Selective Supplement

Shelf Life (days)	1095
Storage Temp (°C)	10-30°C
Light Sensitive	Yes
Dehydrated Medium Appearance	Fine Powder
Dehydrated Medium Colour	Beige
Prepared Medium Appearance	Firm Gel
Prepared Medium Colour	Straw
Prepared PH	7.2 ± 0.2
Recommended Incubation	Aerobically at 37±1°C for 24-48 hours

Shelf Life (days)

1095

Storage Temp (°C)

10-30°C

Light Sensitive

Yes

Dehydrated Medium Appearance

Fine Powder

Dehydrated Medium Colour

Beige

Prepared Medium Appearance

Firm Gel

Prepared Medium Colour

Straw

Prepared PH

7.2 ± 0.2

Recommended Incubation

Aerobically at 37±1°C for 24-48 hours

Formula*

g/L

Enzymatic digest of animal tissue

18.0

Enzymatic digest of casein

6.0

Yeast extract

10.0

Sodium pyruvate

2.0

Glucose

2.0

Magnesium glycerophosphate

1.0

Magnesium sulphate

0.5

Sodium chloride

5.0

Lithium chloride

10.0

Disodium hydrogen phosphate

2.5

5-Bromo-4-chloro-3-indolyl-ß-Dglucopyranoside

0.05

Agar

12.0

Total

69.0

*Adjusted/supplemented as required to meet performance requirements

Preparation

Suspend 69.0g of dried culture medium in 950ml of deionised/purified water and mix for 10 minutes.

Autoclave to sterilise at 121°C for 15 minutes then cool in a water bath to 45-50°C and aseptically add 1 vial of selective supplement (E&O LS0210) and 50ml of Primary Listeria Diagnostic Supplement (E&O BM8050).

Gently mix the final medium before aseptically dispensing the specified volume into appropriate sterile containers and allowing to cool.

Organisms	Ref. No	Result
L. monocytogenes	ATCC 13932	Growth: Blue/green colonies with halo
L. monocytogenes	NCTC 11994	Growth: Blue/green colonies with halo
L. monocytogenes	NCTC 7973	Growth: Blue/green colonies with halo
L. innocua	NCTC 11288	Growth: Blue/green colonies with NO halo
E. coli	NCTC 12241	Inhibited
E. coli	ATCC 8739	Inhibited
E. faecalis	NCTC 12697	Inhibited
E. faecalis	NCTC 775	Inhibited
S. cerevisiae	NCPF 3178	Inhibited