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    INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY

    WORLD HEALTH ORGANIZATION



    Toxicological evaluation of certain veterinary drug
    residues in food



    WHO FOOD ADDITIVES SERIES 39





    Prepared by:
    The forty-eighth meeting of the Joint FAO/WHO Expert
    Committee on Food Additives (JECFA)



    World Health Organization, Geneva 1997


    Antimocrobial Agents

         The Committee examined the results of studies of antimicrobial
    activity  in vitro in which relevant gut microflora were used to
    calculate ADIs for some of the antimicrobial agents that were
    reviewed. The equation used for deriving the ADIs is based on that
    shown in Annex 5 of the report of the thirty-eighth meeting of the
    Committee (Annex 1, reference 97). The equation was modified at the
    forty-seventh meeting (Annex 1, reference 125), and the modified
    version was used to derive ADIs based on microbiological activity at
    the present meeting.

         The upper limit of the ADI was derived as follows:


                Upper limit      MIC50 (g/g)      MCC (g)
                  of ADI      =                           
                (g/kg bw)       FA      SF      BW (kg)


    where:

    MIC50   =      The minimum concentration of an antimicrobial drug that
                   completely inhibits the growth of 50% of cultures of a
                   given microorganism, as judged by the naked eye, after
                   a given period of incubation. For the purposes of the
                   evaluation, the MIC50 value is the mean MIC50
                   value(s) for the strain(s) of the relevant species
                   tested. Alternatively, the lowest MIC50 value for the
                   most sensitive species can be used.

    MCC  =         Mass of colonic content; a value of 220 g is used.

    FA   =         Fraction of an oral dose available to act upon
                   microorganisms in the colon

    SF   =         The safety factor used to account for uncertainty about
                   the amount and relevance of data for MIC values
                   available for review; may range from 1 to 10, a value
                   of 1 being used when extensive, relevant
                   microbiological data are available.

    BW   =         Body weight; a value of 60 kg is used.

    


    See Also:
       Toxicological Abbreviations
       Antimicrobial agents (WHO Food Additives Series 41)