Paragraph 6 Examination of cultures

All colonies (including “pin-point” colonies) on each plate shall be counted and the arithmetic mean count obtained. To facilitate counting it is desirable to use a counting chamber, a suitable lens and a tally counter. The result of the count shall be recorded as the number of bacteria per ml. and shall be to the nearest 10, 100 or 1,000 according to whether a dilution of 1 in 10,1 in 100 or 1 in 1,000 has been used.