Overnight concentration of urine. Natural defense mechanism against urinary tract infection.

Growth of Escherichia coli 06 was compared in concentrated overnight urine and dilute daytime urine. In concentrated urine, 90 per cent of the initial inoculum died during the lag phase and surviving bacteria had a long lag period before they started to grow. Once growth began, these bacteria required fifty-five hours to reach their maximum growth yield. In dilute urine, 75 per cent of the same bacteria survived the lag phase; once growth began, they reached maximum growth yield in only thirteen hours. These observations suggest that concentrated overnight urine serves as a natural defense mechanism against urinary tract infections.