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Molecular pathogen identification comes to the bedside

Reporter:  Larry H Bernstein, MD, FCAP

The developments in molecular diagnostics have been proceeding at a rapid pace.  Naturally it is not surprising that it would reach into clinical microbiology early.  Microbiology and virology have many methods for validation of type of pathogen, and the identification of new pathogens can require delay because of use of a State laboratory.  This will be less an issue with the consolidation of regional facilities and associated laboratories.

I present an example of point-of-care technology from the University of California, Davis developed by Gerald Kost and colleagues with UC Lawrence Livermore National Point-of-Care Technologies Center .

Tran NK, Wisner DH, Albertson TE, Cohen S, et al.  Multiplex polymerase chain reaction pathogen detection in patients with suspected septicemia after trauma, emergency, and burn surgery. Surgery 2012 Mar;151(3):456-63. Epub 2011 Oct 5.  nktran@ucdavis.edu

The goal of the study:  to determine the clinical value of multiplex polymerase chain reaction (PCR) study for enhancing pathogen detection in patients with suspected septicemia after trauma, emergency, and burn surgery.

Finding: PCR-based pathogen detection quickly reveals occult bloodstream infections in these high-risk patients and may accelerate the initiation of targeted antimicrobial therapy.

Type study: a prospective observational study

Population:  30 trauma and emergency surgery patients compared to 20 burn patients.

Method:  Whole- routine blood cultures (BCs) were tested using a new multiplex, PCR-based, pathogen detection system. PCR results were compared to culture data.

Arbitrated Case Review

Arbitrated case review was performed by a medical intensivist, 3 trauma surgeons, 3 burn surgeons, 1 microbiologist, and an infectious disease physician to determine antimicrobial adequacy based on paired PCR/BC results. The arbitrated case review process is adapted from a previous study. Physicians were first presented cases with only BC results. Cases were then represented with PCR results included.

Results:

  • PCR detected rapidly more pathogens than culture methods.
  • Acute Physiology and Chronic Health Evaluation II (APACHE II), Sequential Organ Failure Assessment (SOFA), and Multiple Organ Dysfunction (MODS) scores were greater in PCR-positive versus PCR-negative trauma and emergency surgery patients (P ≤ .033).
  • Negative PCR results (odds ratio, 0.194; 95% confidence interval, 0.045-0.840; P = .028) acted as an independent predictor of survival for the combined surgical patient population.

CONCLUSION:

  • PCR results were reported faster than blood culture results.
  • Severity scores were significantly greater in PCR-positive trauma and emergency surgery patients.
  • The lack of pathogen DNA as determined by PCR served as a significant predictor of survival in the combined patient population.
  • PCR testing independent of traditional prompts for culturing may have clinical value in burn patients.

NK Tran, et al.  Multiplex Polymerase Chain Reaction Pathogen Detection in Trauma, Emergency, and Burn Surgery Patients with Suspected Septicemia.  Surgery. 2012 March; 151(3): 456–463. PMID: 21975287 [PubMed – indexed for MEDLINE] PMCID: PMC3304499 On-line 2011 October 5.
doi:  10.1016/j.surg.2011.07.030
PMCID: PMC3304499.  NIHMSID: NIHMS288960

Plymerase chain reaction, PCR

Plymerase chain reaction, PCR (Photo credit: Wikipedia)

 

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