Use of droplet plating method and cystine-lactose-lactng electrolyte-deficient medium in routine quantitative urine culturing procedure

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Abstract
Droplet plating of 0.01 ml of 10-2 dilutions of mixed sonically treated [human] urines [to detect bacteruria] onto cystine-lactose electrolyte-deficient agar permits formation of discrete, easily counted colonies within a small circumscribed area without interference by Proteus overswarm. Each colony is considered as arising from a single viable cell. The single dilution permits precise reproducible quantitation of urine bacteria population within the range 104-106 cells/ml of sample. Droplet-plated counts were consistently (.apprx.) double those determined by standard pour plate quantitation. The method requires only inexpensive readily available materials and is performed routinely in a large-volume clinical laboratory.