Perfringens Agar

(O.P.S.P. )

LAB 109

Description

This medium was developed by Handford in 1974 to overcome some of the problems associated with enumerating Clostridium perfringens in foods. The medium is buffered and utilises sodium metabisulphite and liver extract as sources of H₂S with ferric ammonium citrate as the indicator. The medium is made selective with the addition of X109 Sulphadiazine and X110 Oleandomycin/Polymyxin supplements.

1.42

Method for reconstitution

Weigh 45.5 grams of powder, disperse in 1 litre of deionised water. Allow to soak for 10 minutes then sterilise by autoclaving at 121˚C for 15 minutes. Allow to cool to 47˚C before adding 2 vials each of selective supplements X109 and X110.

Appearance: Pale straw, clear.

pH: 7.3 ± 0.2

Minimum Q.C. organisms: C. perfringens NCIMB 50027 E. coli NCIMB 50034 (inhibition)

Storage of prepared medium: Use on day of preparation.

Inoculation: Pour plates, 1ml sample plus 9ml medium. When set overlay with sterile medium.

Incubation: 37˚C anaerobically for 24 hours.

Interpretation: Count large black colonies, presumptively identified as C. perfringens.

References

Handford, P.M. (1974). A new medium for the detection and enumeration of C. perfringens in foods. J. Appl. Bact. 37: 559-570.

Shahidi, S.A. and Ferguson, A.R. (1971). A new quantitative and confirmatory medium for C. perfringens in food. Appl. Microbiol. 21: 500-506.

Marshall, R.S., Steenberger, J.F. and McClung, L.S. (1965). Appl. Microbiol. 13: 559. A rapid technique for the enumeration of C. perfringens.

Pharmacopoeia of culture media for food microbiology. (1987). Int. J. Food Microbiol. 5: 3: 240-241.

References

Reasoner, D.J., Geldreich, E.E. (1985) A New Medium for the Enumeration and Subculture of Bacteria from potable water. App & Env. Microbiol. Jan. 1985 p.1-7.

American Public Health Association (1985) Standard Methods for the Enumeration of Water and Wastewater. 16th Edition. American Public Health Association Inc. Washington D.C.

Environment Agency: The Microbiology of Drinking Water (2002). Methods for the Examination of Water and Associated Materials.