Comparative study of diagnosis of PD peritonitis by quantitative polymerase chain reaction for bacterial DNA vs culture methods.
BACKGROUND
Peritonitis remains one of the main complications that afflict peritoneal dialysis patients. We conducted a pilot study to determine the feasibility and potential advantages of quantitative PCR (qPCR) assays for the presence of bacterial DNA in this clinical scenario.


METHODS
14 patients attending with 'cloudy bags' had PD fluid analyzed in accordance with Renal Association Standards. In addition, quantitative bacterial DNA analysis was performed on 50 mL samples of PD fluid. DNA was extracted using a Qiagen kit. Quantitative PCR assays using primers and probes targeted at 16S rDNA were used to measure the levels of bacterial DNA. Samples from 13 patients attending the department for other reasons served as negative controls. Laboratory staff were blinded to clinical details at the time of analysis.


RESULTS
We determined a threshold of bacterial DNA whereby 11 of 13 negative controls were 'negative'. Significant bacterial DNA was found in 6 of 9 culture positive' peritonitis cases (p < 0.05 by chi(2). The 3 cases of 'no growth' peritonitis had 'insignificant' bacterial DNA. Serial DNA analysis was performed in 8 patients. Of the 6 patients who were 'cured' with standard antibiotic therapy, only 1 showed a rise in bacterial DNA from Day 1 to 5. But the 2 patients who relapsed after antibiotics had marked rises in bacterial DNA (p < 0.05 by chi(2).


CONCLUSIONS
We showed that results from quantitative bacterial DNA PCR assays correlate with current microbiological tests despite the small size of this study. We also suggest that this technology might be clinically useful as an adjunct for cases of 'no growth' peritonitis and to identify those patients likely to relapse despite apparent clinical improvement with standard antibiotic therapy.
Johnson
Gemma
G
Department of Medical Microbiology, Barts and The London NHS Trust, Whitechapel, UK.
Wilks
Mark
M
Warwick
Simon
S
Millar
Mike R
MR
Fan
Stanley L-S
SL
D001419:Bacteria / Q000235:genetics* / Q000302:isolation & purification*; D001424:Bacterial Infections / Q000175:diagnosis* / Q000209:etiology / Q000382:microbiology; D046508:Culture Techniques; D004269:DNA, Bacterial / Q000032:analysis*; D003937:Diagnosis, Differential; D006801:Humans; D010530:Peritoneal Dialysis / Q000009:adverse effects*; D010538:Peritonitis / Q000175:diagnosis* / Q000209:etiology / Q000382:microbiology; D010865:Pilot Projects; D016133:Polymerase Chain Reaction; D015203:Reproducibility of Results
D004269:DNA, Bacterial