[Improved filter paper method for semiquantitative colony count in urine. Comparison with the counting plate...

A semiquantitative differential colony count of 10(4)-10(9) colonies/ml is quickly prepared by absorbing bacterial suspensions on suitable filter paper strips and subsequent printing on solid media. Single colonies permit firstly the important distinction of mixed and pure cultures, and secondly the immediate resistance test and differentiation. The immersion method using filter paper or agar carriers lacks these two advantages with colonies exceeding 10(5)/ml. Small samples of 1 ml suffice. The reliability and good reproducibility of the filter absorption method were demonstrated by comparison with counting plates, using several hundred samples of pure and mixed cultures of various bacteria with different filter papers and 1024 urine samples with the same type of filter paper. Owing to the small expenditure of material and time, this method is suitable as a screening test in urinary tract infections.