Tryptic Soy Agar (CASO) with Polysorbate 80 and Lecithin

Tryptic Soy Agar with Polysorbate 80 and Lecithin
Microbial Content Test Agar

Cat. No. 1.07324.0500
(500 g)

Medium for environmental monitoring and for determining efficiency of containers, equipment and surfaces.

Mode of Action	Experimental Procedure and Evaluation
Typical Composition (g/liter)	Quality Control
Preparation	Literature

Mode of Action
Casein and soy peptones provide the replication of even fastidious microorganisms. Sodium chloride maintains osmotic equilibrium. QUISNO et al. (1946), BRUMMER (1976) and ERLANDSON et al. (1953) reported that Lecithin and Polysorbate 80 inactivate many residual desinfectants. Polysorbate 80 neutralizes phenols, hexachlorophene and formalin. Lecithin inactivates quaternary ammonium compounds.

Typical Composition (g/liter)
Peptone from casein 15.0; peptone from soymeal 5.0; sodium chloride 5.0; polysorbate 80 5.0; lecithin 0.7; agar-agar 15.0.

Preparation
Suspend 45.7 g in 1 liter of distilled or dem. water and heat to boiling, if necessary, with frequent agitation until completely dissolved. Autoclave at 121°C for 15 minutes.
Cool the medium to about 45°C, mix well and pour in Petri dishes or RODAC (Replicate Organism Detection and Counting) plates (about 17 ml).
pH 7.3 ± 0.2 at 25°C.
The prepared medium is clear and yellowish-brown.

Experimental Procedure
Inoculate the medium by spreading method (in Petri dish). Using RODAC plates for checking the cleanliness and disinfection efficiency of surfaces, press the plate with even pressure onto the surface. Avoid rubbing to prevent damage of the agar bed. Clean the surface afterwards to remove any remainings of the agar.
Incubation: 24-48 hours at 35 ± 2°C aerobically.

Quality control

Test strains	Growth after 24 hours	Pigment	Colony color
Staphylococcus aureus ATCC 25923	good / very good	-	Yellow to white
Pseudomonas aeroginosa ATCC 10145	good / very good	+	Green-blue

Literature

QUISNO, R., I. W. GIBBY, AND M. J. FOTER: A neutralizing medium for evaluating the germicidal potency of the quaternary ammonium salts. – Am. J. Pharm., 118; 320-323 (1946).
BRUMMER, B.: Influence of possible disinfectant transfer on Staphylococcus aureus plate counts after contact sampling. – App. Environ. Microbiol., 32; 80-84 (1976).
ERLANDSON, A. L., Jr., and C. A. LAWRENCE: Inactivating medium for hexachlorophene (G-11) types of compounds and some substituted phenolic disinfectants. – Science, 118; 274-276 (1953).