Prevalence of unsuspected urinary bacterial contamination: effects of screening tests for detection of inborn errors of metabolism.
Hospitals and doctors submitting urine samples to a central reference laboratory screening for inborn errors of metabolism had been given precise instructions on sample handling designed to prevent growth of contaminating bacteria. 140 consecutive samples were examined bacteriologically and 22% had a heavy growth of bacteria (greater than 10(5) organisms/ml). Contamination was commonest in samples from children under 2 years. Normal human urine samples spiked with various amino acids were inoculated with pure cultures of different urinary pathogens and then incubated, with control samples, at 37 degrees C. Urinary amino acids were measured either semi-quantitatively by high-voltage electrophoresis or quantitatively by ion-exchange chromatography. Very wide-ranging changes in amino acid levels were noted in some inoculated samples after incubation. In two urine samples spiked with 8 mg/ml arginine, this had disappeared after 24-48 h. Unsuspected urinary bacterial contamination may be a more important source of false positive and false negative results in the investigation of disorders of amino-acid metabolism than previously supposed.
D000592:Amino Acid Metabolism, Inborn Errors / Q000175:diagnosis* / Q000652:urine; D001419:Bacteria / Q000378:metabolism; D006801:Humans; D007223:Infant; D008403:Mass Screening; D014556:Urine / Q000382:microbiology*