A real-time PCR-based semi-quantitative breakpoint to aid in molecular identification of urinary tract infections

PLoS One. 2013 Apr 23;8(4):e61439. doi: 10.1371/journal.pone.0061439. Print 2013.

Abstract

This study presents a novel approach to aid in diagnosis of urinary tract infections (UTIs). A real-time PCR assay was used to screen for culture-positive urinary specimens and to identify the causative uropathogen. Semi-quantitative breakpoints were used to screen for significant bacteriuria (presence of ≥ 10(5) CFU/ml of uropathogens) or low-level bacteriuria (containing between 10(3) and 10(4) CFU/ml of uropathogens). The 16S rDNA-based assay could identify the most prevalent uropathogens using probes for Escherichia coli, Pseudomonas species, Pseudomonas aeruginosa, Staphylococcus species, Staphylococcus aureus, Enterococcus species and Streptococcus species. 330 urinary specimens were analysed and results were compared with conventional urine culture. Using a PCR Ct value of 25 as semi-quantitative breakpoint for significant bacteriuria resulted in a sensitivity and specificity of 97% and 80%, respectively. In 78% of the samples with monomicrobial infections the assay contained probes to detect the bacteria present in the urine specimens and 99% of these uropathogens was correctly identified. Concluding, this proof-of-concept approach demonstrates that the assay can distinguish bacteriuria from no bacteriuria as well as detect the involved uropathogen within 4 hours after sampling, allowing adequate therapy decisions within the same day as well as drastically reduce consequent urine culturing.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Bacteriuria / diagnosis*
  • Bacteriuria / microbiology
  • Child
  • Child, Preschool
  • Enterococcus / classification
  • Enterococcus / genetics
  • Enterococcus / isolation & purification
  • Escherichia coli / genetics
  • Escherichia coli / isolation & purification
  • Female
  • Humans
  • Infant
  • Infant, Newborn
  • Male
  • Middle Aged
  • Pseudomonas / classification
  • Pseudomonas / genetics
  • Pseudomonas / isolation & purification
  • RNA, Ribosomal, 16S / classification
  • RNA, Ribosomal, 16S / genetics
  • RNA, Ribosomal, 16S / isolation & purification*
  • Real-Time Polymerase Chain Reaction / methods*
  • Sensitivity and Specificity
  • Staphylococcus / classification
  • Staphylococcus / genetics
  • Staphylococcus / isolation & purification
  • Streptococcus / classification
  • Streptococcus / genetics
  • Streptococcus / isolation & purification
  • Urinary Tract Infections / diagnosis*
  • Urinary Tract Infections / microbiology
  • Urine / microbiology

Substances

  • RNA, Ribosomal, 16S

Grants and funding

No external funding, apart from the support of the authors’ institution, was available for this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.