AS/NZS 4276.20:2003 (R2013)

Scope

This Standard sets out a method for detecting coagulase positive staphylococci and Staphylococcus aureus (S.aureus) in water by the membrane filtration method.
NOTES:
1 Membrane filtration is suitable for enumerating microorganisms only when the turbidity of the water is low.
2 The optimum range for membrane filter counts is 20-80 colonies. If the confirmed total count from one or more membranes is less than 20, then the derived sample count, which is an estimate of the true count in the sample (population parameter), is regarded as having a low precision. At the other extreme, when membranes containing greater than 80 colonies are counted, the counting error tends to be large. Again, the derived counts are regarded as having low precision. Derived counts of low precision should be indicated on reports by flagging them as ‘estimated’ or ‘approximate’.
3 A flow diagram of the procedure is shown in Appendix A.