Modifications of the calcium alginate swab technique recommended as an alternative to cotton swabs in Standard Methods for the Examination of Dairy Products, American Public Health Association, 1960 are presented. The modifications are based on observed lysis of some gram negative bacteria during dissolution of the swab with sodium hexametaphosphate (HEX) and inhibition of some gram positive bacteria when the solvent is included in certain plating media. Since NaCl protects cells against lysis, Ringers' solution is suggested as the swab buffer for sample collecting. During dissolution of the swab HEX concentration should be 2% or less in order to minimize carry-over to the plating medium. Several plating media were studied and trypticase soy agar or its equivalent as determined with a sensitive gram positive organism such as Sarcina lutea is recommended. It is also recommended that contact time between cells and HEX be as short as possible and that 20 ml of plating medium be used for each ml of HEX-alginate-Ringers' sample.

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