[Quantitative and qualitative bacteriological studies on urine specimens obtained by suprapubic needle aspiration and...

In 398 patients with suspected urinary tract infection, quantitative and qualitative bacteriological studies were conducted in urine samples obtained by suprapubic needle aspiration of the bladder (BPU) and in midstream-voided specimens (MSU) collected immediately following the aspirations. In MSU, bacteria were found in 96.5% of all cases and in BPU in only 38.2%. Of the infected MSU, 63.3% showed mixed infections, while mixed cultures were found in only 11.2% of infected BPU. In 80% of the investigated patients, the MSU contained at least one more type of bacteria than the BPU, thus indicating urethral contamination. Of the patients with bladder bacteriuria, only 74% had bacterial counts of 10(5)/ml or more in the midstream-voided urine. Accordingly, 26% of the urinary tract infections diagnosed by bladder aspiration would not have been recognized on the basis of a single bacterial count in the midstream-voided urine. On the other hand, about 4% of patients with bacterial counts of 10(5)/ml or more in the MSU had a sterile bladder aspirate. In 72.4% of the infected BPU, E. coli was found, followed in frequency by Enterococcus (14.5%). In the infected MSU, however, Enterococcus was more frequent than C. coli (65.6% and 61.7% respectively). Thus, E. coli appears to be the most important etiological species in infections of the bladder and the kidneys, while Enterococcus seems to be the most frequent contaminant during urethral passage. The most frequent bacterial combination in mixed cultures in both BPU and MSU was that of E. coli and Enterococcus.