Colony Counts on Strips of Agar in Tubes

SUMMARY: For viable counting, 0.1 ml. volumes of bacterial suspension were incorporated in 1.5-2 ml. nutrient agar, which after mixing was allowed to solidify in an almost horizontal test-tube so as to produce a 3–4 in. agar strip. After incubation in the vertical position, the counts of the strips gave estimates of a bacterial population which did not differ significantly from that obtained from plates inoculated with 1 ml. quantities.