Boric acid converts urine into an effective bacteriostatic transport medium.

Results of an experiment designed to assess the usefulness of boric acid for preserving urine before its bacteriological examination are reported. Boric acid at a concentration of 20 g/l was found to be usefully bacteriostatic, largely eliminating the false positive results obtained with unpreserved specimens when delay before culture was more than 90 min. The effect lasted for up to 48 h. There was no evidence that borate is toxic to the urinary pathogens encountered in naturally infected urine. Borate also preserves white blood cells in urine and thereby marginally improved the diagnosis of pyuria. The results confirm that boric acid may with benefit be added to bottles used for transporting specimens of urine to the laboratory.