Nitristic are test strips used to detect the presence of nitrite-producing bacteria in urine. Most urinary tract infections are caused by such bacteria, for example E. coli. A positive test is a sure indication of a urinary tract infection. Doctors should be contacted for further investigation and possible treatment. Nitristic test strips detect bacteria in the urine, even without symptoms. Dip the stick with the paper part into the urine. Results are displayed within 10 seconds.