E.E. Broth

(Enterobacteriaceae Enrichment Broth)

LAB 91

Description

E.E. Broth is recommended as an enrichment medium when examining food and feedstuffs for Enterobacteriaceae. It is a modification of LAB 51 Brilliant Green Bile Broth, with an improved buffering capacity to encourage early growth and prevent autosterilization. E.E. Broth uses glucose instead of lactose to make the medium a test for all enterobacteria including non lactose fermenting organisms.

Method for reconstitution

Weigh 43.5 grams of powder and add to 1 litre of deionised water. Swirl to dissolve, warm gently if necessary, then distribute into bottles or tubes and heat at 100˚C for 30 minutes only. Cool rapidly. OVERHEATING THIS MEDIUM WILL ADVERSELY AFFECT ITS PERFORMANCE.

Appearance: Green, clear.

pH: 7.2 ± 0.2

Minimum Q.C. organisms: E. coli NCIMB 50034 B. subtilis (inhibition)

Storage of Prepared Medium: capped containers - up to 3 months at 15-20˚C in the dark.

Inoculation: Add 1 part of sample suspension or dilution to 10 parts of medium.

Incubation: 44˚C for 18 hours for thermotrophs. 32˚C for 24-48 hours for mesotrophs. 4˚C for 10 days for psychrotrophs.

Interpretation: Turbidity and a colour change to yellow-green is presumptive evidence of Enterobacteriaceae. Subculture onto confirmatory media e.g. LAB 88 V.R.B.G.A. must be carried out.

References

Mossel, D. A. A., Visser, M. and Cornelissen, A. M. R. 1963. The examination of foods for Enterobacteriaceae using a test of the type generally adopted for the detection of salmonellae. J.Appl. Bacteriol. 26, 444-452.

Mossel, D. A. E., Harrewijn, G. A. and Nesselrooy-van Zadelhoff, C. F. M. 1974. Standardisation of the selective inhibitory effect of surface active compounds used in media for the detection of Enterobacteriaceae in food and water. Health Lab. Sci. 11, 260-267. Richard, N. 1982. Monitoring the quality of selective liquid media by the official French dilution technique used for the bacteriological examination of foods. In: Quality assurance and quality control of microbiological culture media, edited by J. E. L. Corry, G.I.T.-Verlag Darmstadt, pp. 51-57.