Usefulness of 23S rRNA amplification by PCR in the detection of bacteria in CAPD peritonitis

Peritonitis is the most common complication of continuous ambulatory peritoneal dialysis (CAPD), and the spectrum of organisms causing CAPD peritonitis is broad. Polymerase chain reaction (PCR) has recently broadened its diagnostic capabilities in infectious diseases. PCR can provide a sensitive method for identifying causative infectious organisms.

To evaluate the usefulness of 23S bacterial ribosomal RNA amplification and direct sequencing for the detection of infectious organisms, we compared PCR with bacteriological culture for the analysis of dialysates from CAPD peritonitis patients. Thirty-two samples from CAPD peritonitis patients with current antibiotic use and control samples from 30 CAPD patients without peritonitis were examined by PCR with sequencing analysis and by conventional bacteriological culture. In addition, 95 culture-positive samples and 39 culture-negative samples from CAPD peritonitis patients before antibiotic treatment were analyzed by PCR assay.

In the control samples from patients without CAPD peritonitis, false-positive rates were relatively rare: 3 of 30 in the PCR study and 2 of 30 in the culture study. Of the 134 CAPD peritonitis samples collected before antibiotic therapy, positive cultures were obtained in 70.9% (95/134) of them. In 75 of the culture-positive samples, the same microorganisms were confirmed by PCR assay, and the others showed discrepant results as compared with culture study. In 30 of the 39 culture-negative samples, microbial organisms were detected by PCR assay. Of the 32 samples from patients who developed CAPD peritonitis during antibiotic treatment, 17 (53.1%) were positive by PCR assay, and 5 (15.6%) were positive by culture.

Our study suggests that broad-spectrum PCR with RNA sequencing can complement culture methods in the diagnosis of CAPD peritonitis, especially in patients with previous or current antibiotic use.