title: Rapid label-free identification of mixed bacterial infections by surface plasmon resonance.
abstract: BACKGROUND
  Early detection of mixed aerobic-anaerobic infection has been a challenge in clinical practice due to the phenotypic changes in complex environments. Surface plasmon resonance (SPR) biosensor is widely used to detect DNA-DNA interaction and offers a sensitive and label-free approach in DNA research.
  
  
  METHODS
  In this study, we developed a single-stranded DNA (ssDNA) amplification technique and modified the traditional SPR detection system for rapid and simultaneous detection of mixed infections of four pathogenic microorganisms (Pseudomonas aeruginosa, Staphylococcus aureus, Clostridium tetani and Clostridium perfringens).
  
  
  RESULTS
  We constructed the circulation detection well to increase the sensitivity and the tandem probe arrays to reduce the non-specific hybridization. The use of 16S rDNA universal primers ensured the amplification of four target nucleic acid sequences simultaneously, and further electrophoresis and sequencing confirmed the high efficiency of this amplification method. No significant signals were detected during the single-base mismatch or non-specific probe hybridization (P < 0.05). The calibration curves of amplification products of four bacteria had good linearity from 0.1 nM to 100 nM, with all R(2) values of >0.99. The lowest detection limits were 0.03 nM for P. aeruginosa, 0.02 nM for S. aureus, 0.01 nM for C. tetani and 0.02 nM for C. perfringens. The SPR biosensor had the same detection rate as the traditional culture method (P < 0.05). In addition, the quantification of PCR products can be completed within 15 min, and excellent regeneration greatly reduces the cost for detection.
  
  
  CONCLUSIONS
  Our method can rapidly and accurately identify the mixed aerobic-anaerobic infection, providing a reliable alternative to bacterial culture for rapid bacteria detection.
authors.affiliation: Department of Laboratory Medicine, Southwest Hospital, the Third Military Medical University, Chong Qing, PR China.
authors.forename: Jue
authors.initials: J
authors.lastname: Wang
authors.forename: Yang
authors.initials: Y
authors.lastname: Luo
authors.forename: Bo
authors.initials: B
authors.lastname: Zhang
authors.forename: Ming
authors.initials: M
authors.lastname: Chen
authors.forename: Junfu
authors.initials: J
authors.lastname: Huang
authors.forename: Kejun
authors.initials: K
authors.lastname: Zhang
authors.forename: Weiyin
authors.initials: W
authors.lastname: Gao
authors.forename: Weiling
authors.initials: W
authors.lastname: Fu
authors.forename: Tianlun
authors.initials: T
authors.lastname: Jiang
authors.forename: Pu
authors.initials: P
authors.lastname: Liao
mesh_terms: D001419:Bacteria / Q000235:genetics / Q000302:isolation & purification; D001424:Bacterial Infections / Q000175:diagnosis*; D001483:Base Sequence; D002138:Calibration; D004587:Electrophoresis, Agar Gel; D006801:Humans; D057230:Limit of Detection; D016133:Polymerase Chain Reaction; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013194:Staining and Labeling; D020349:Surface Plasmon Resonance / Q000379:methods*