The counting of surface colonies of bacteria

Abstract

A colony count performed by spreading a known volume of suspension on the surface of a plate possesses certain advantages over other methods, of which the chief is ease of counting.The distribution of counts of several samples of the same suspension on medium of the same age and batch is as expected on statistical grounds.Different batches and ages of blood plates may give substantially the same count but this is not true for Leifson's and Wilson & Blair's media.A diluting fluid, which is satisfactory if blood agar is the plating medium, may not necessarily be so if special media are to be used.