Rapid identification of blood cultures

 

By Mark J. Ingerman, M.D., FACP, Chief, Infectious Diseases and Chief, Infection Prevention and Control

 

New molecular diagnostic techniques are now available for rapid identification of bacterial and viral pathogens. MLHS Clinical labs have already instituted the rapid identification viral panel at MLHS. Although a costly test, 34% of all tests ordered have been diagnostic for a viral pathogen, pertussis, mycoplasma or chlamydia. This testing process assists in reduction of unnecessary antibiotic therapy, and directs medical therapy for the infectious process. This test needs to be used in a judicious manner both for inpatients and outpatients.

 

In early 2017, a pilot will begin at LMC to evaluate use of the molecular BioFire FilmArray system to rapidly identify bacterial & yeast pathogens in positive blood cultures.  Current culture-based methods require pathogen isolation for definitive identification & antimicrobial susceptibility testing, a process that can take up to 48-72 h after a positive blood culture is detected.  In the pilot, at the time a blood culture is detected as positive for growth, an aliquot will be tested with a BioFire panel.  BioFire BCID panels identify 24 pathogens and 3 antimicrobial resistance makers (see Table below) with a turnaround time of a little over one hour. Based on a historical review of positive blood cultures at MLH, it is anticipated that >85% of blood cultures will be identified within 90 minutes of becoming positive.

 

Once BioFireBCID panel has been performed, the nursing floor will be notified of this critical value. It will be expected that a medical provider will be notified within 30 minutes. It will be the responsibility of that medical caregiver to respond to this critical value with either initiation of antibiotics, modifying antibiotics or terminating antibiotic therapy depending upon the results.   For example, if the BCID panel identifies Staphylococcus aureus methicillin susceptible (MSSA) it may be possible to stop vancomycin.   Infectious Disease is available for a consultation to guide therapy regarding the BioFire results.

 

All positive blood cultures tested with BioFire BCID will still be subcultured to obtain isolates for complete susceptibility tests, which will be available 48-72 h after the culture is identified as positive.

 

Rapid identification of pathogens from positive blood cultures by molecular methods, when coupled with antimicrobial stewardship interventions, can improve the time to optimization of antimicrobial therapy, contribute to improved patient outcomes and reduce healthcare costs.

 

Once the pilot of the BioFire BCID panel is completed at Lankenau successfully,  it is expected to be rolled out to the other hospitals.

 

Organisms and Resistance markers Detected by the Biofire FilmArray BCID Panels

Gram-Positive Bacteria Gram-Negative Bacteria Yeast
Enterococcus spp. Acinetobacter baumannii Candida albicans
Listeria monocytogenes Enterobacteriaceae Candida glabrata
Staphylococcus    Enterobacter cloacae complex Candida krusei
   Staphylococcus aureus    Escherichia coli Candidia parapsilosis
Streptococcus    Klebsiella oxytoca Candida tropicalis
   Streptococcus agalactiae  (Group B)     Klebseilla pneumonia Antimicrobial Resistance Genes
   Streptococcus pneumonie    Proteus spp mecA – methicillin resistance
   Streptococcus pyogenes (Group A)    Serratia marcescens vanA/B – vancomycin resistance
  Haemophilus influenza KPC – carbapenem resistance
Neisseria meningitides  
Pseudomonas aeruginosa

 

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