AS 4659.1:2015 – Guide to determining the equivalence of food microbiology test methods Part 1: Qualitative tests
AS 4659.1:2015 – Guide to determining the equivalence of food microbiology test methods Part 1: Qualitative tests.
3.4 False ncgatkc
When the alternate method yields a negative result but the rekrence method 3.ields a positive result,
3$ Fake poitkc
Whcn the alternate method yields a positive result but the reference method yields a negative result.
NOTIi: A false positive’ may be a true positive which was not detected by the reference method. Such occurrences need to be carefully verified; howcer, for the purpose of this Standard they will be considered false positives because the Standard is aimed at demonstrating the equivalence of the two methods and is also applicable to the analysis of non-identical lest samples, i.e. where the primalv enrichment is different.
3.6 Fractional rrcovcrx
Validation criteria that arc satisfied when replicate samples of either the alternative or reference method yield 50% (range 25%—75/.) positive responses.
The food sample in which the target organism is to be detected.
The result given by the method at a point where a decision may be made as to whether or not the matrix may contain the target organism. The method continues to confinn whether the presumptive result is in fact a positive result.
3.9 Reference culture
The culture designated in the appropriate Australian Standard mcthod
3.10 Reference method
The Australian Standard method against which the alternate method will be compared.
3,11 Target organism
The genus. species. antigenically. toxicologically or physiologically defined group of organisms which the reference method is designed to detect.
4.1 l)efine the equlsalence determination
The equivalence determination should be defined in terms of the following:
(a) The target organism’s genus, species. serotype. etC.
(hI The matrix under examination: the food and the characteristics that define it. e.g. the matrix should be defined in terms of characteristics such as pH, solids level, water activity, presence and composition of preservatives, season of production, brand name. etc. depending upon the nature of the matrix.
The procedures outlined in the Standard should be repealed for each matrix intended for use with the alternate method.
NOTIi: When determining equivalence of an alternate method the laboratory should select the matrices to he included in the esalualion from those within the scope of the standard method. This Standard is not intended tor the validation of matrices outside of the scope of either the alternate method or the standard method. Reference should be made to standard tests and the literature to support the choices of matrices. The choice should take into account the range of samples tested by the laboratory and the effects that the natural variation in significant parameters may have on the detection of the target organism.
(c) The alternate method precisely defined by reference to a publication. manufacturer’s instructions and any optional procedures employed, or deviation from. the published method.
(d) The reference method including the specification of any optional steps.
NOTE: lor example, the salidation of the use of XYL agar as an alteniatise to E’alcam agar in the AS 5013.24.1 method for thc detection of LEiierju m000clIogLmes. from sauces containing pepper and a p11 greater than 4.5.
4.2 I)eflnc the conditions of the equivalence determination
The conditions of the equivalence determination should he defined in terms of the following:
(a) The laboratory where testing is performed
(b) Controls observed by the laboratory during testing. for example, controls on the environment of the laboratory, prevention of cross examination, controls on media and reagents, calibration of equipment. etc. where these factors are considered critical to the success of either method.
(c) The stall performing the tests (experience, qualification and the like). (dl The starting and finishing dates of the tests.
(e) The batch numbers of media. reagents. etc. used.
NOTE: This information is defined for the purpose of reporting on the equivalence determination and recording fatoix which may have some bearing on the results obtained. Thsc factors do not necessarily affect ihc veracity of the study.
4.3 Select test organisms
At least five strains of the target organism should be selected, The refcrcncc culture prescribed in the Australian Standard method as a positive control should be one of the five strains. The other strains may be selected from the following list (in order of preference):
(a) Strains of the target organism isolated by the lahorator from previous samples of the matrix under examination.
(bI Strains of the target organism isolated by reference laboratories or industry sources as representative of the strains found in the type of matrix under examination.
(c) Strains of the target organism held by culture collections.
The strains selected should encompass the variation that may be expected to be found within the target organism in the matrix under examination.