[Determination of the bacterial density of the mid-stream urine in premature infants].

Bacteriuria was investigated in midstream urine samples taken from 1255 apparently healthy premature neonate; 24% of the samples had a bacterial count of 10(5) per ml. The results were found to fit the lognormal distribution. We suggest that the diagnosis of urinary tract infection in the preterm should take the clinical state into account and that a bacteriuria of 10(5) per ml should not be considered significant. In our opinion only bacterial counts of 10(7) per ml or higher should be regarded as asymptomatic bacteriurias in this age group, since at this concentration the probability of error is only 4% which is an acceptable limit from the statistical point of view. If an uncontaminated urine specimen is needed in a preterm neonate percutaneous needle aspiration or catheterization of the urinary bladder is essential.