Bacteremia: Interpreting GenMark ePlex® Results – VASP

Background

When BCx turn positive, the lab reports Gram stain and GenMark ePlex® results to help guide empiric therapy, while awaiting further species identification and susceptibilities.

Management 

  • Start empiric antibiotic therapy (based on clinical picture and table below)
  • Consider ordering repeat BCx x2 based on organism to document clearance
    • Repeat for: Staph (MRSA or MSSA), Staph lugdunensis
    • If source control & no endovascular infxn, no need to repeat (most other strep and GNR’s)
  • VUMC antibiograms (https://www.vumc.org/antimicrobial-stewardshipprogram/ antibiograms) can be used to reference typical resistance patterns and most common organisms in blood cultures.
  • Candida in a blood culture is NEVER considered a contaminant

Gram Positive Cocci

Some gram-positive cocci in blood cultures are NEVER considered a contaminant whereas other gram-positive cocci are often contaminants. See algorithm for interpreting GPC in blood cultures on VASP website.

Organism

Resistance Marker

Preliminary Recommendation
Staphylococcus aureus or Staphylococcus lugdunensis ID Consult REQUIRED mecA detected Start vancomycin IV
No mecA detected Start nafcillin or cefazolin Stop empiric vancomycin IV
Staphylococcus epidermidis
  • Often skin contaminant
  • Repeat cultures, start therapy if uncertain
 mecA detected Start vancomycin IV
No mecA detected Start nafcillin or cefazolin Stop empiric vancomycin IV
Other coagulase negative Staph
  • Often skin contaminant
  • Repeat cultures, start abx if uncertain
 Start vancomycin IV
Streptococcus: agalactiae, pyogenes, anginosus Start penicillin IV or CTX IV Stop empiric vancomycin
Streptococcus pneumoniae Start ceftriaxone Stop empiric vancomycin Await PCN sensitivity data
Other Streptococcus
  • May be contaminant
 Start ceftriaxone Stop empiric vancomycin Await PCN sensitivity data
Enterococcus faecalis
ID Consult REQUIRED		 vanA or vanB detected
  • Start daptomycin 8-10mg/kg/day IV
  • Don’t treat w vancomycin IV
  • Contact precautions
No vanA or vanB
  • Start ampicillin
  • Stop empiric vancomycin IV
Enterococcus faecium
ID Consult REQUIRED		 vanA or vanB detected
  • Start daptomycin 8-10mg/kg/day IV
  • Don’t treat w vancomycin IV
  • Contact precautions
No vanA or vanB
  • Start vancomycin IV
  • Follow-up ampicillin sensitivities
Micrococcus
Often if in a single blood culture is skin contaminant
  • Repeat BCx
  • Start vancomycin IV if uncertain

Gram Positive Rods

Organism

Preliminary Recommendation
Listeria monocytogenes
  • Start ampicillin
  • Stop empiric vancomycin IV
Other Gram positive rod (eg Bacillus cereus Corynebacterium, Cutibacterium acnes, Lactobacillus)
  • Often skin contaminant
  • Repeat cultures, start therapy if uncertain
  • Start vancomycin IV
  • Follow-up sensitivities; some GPRs are resistant to vancomycin

Gram Negative Rods 

*Consult ID if carbapenem resistance detected*

Organism

Preliminary Recommendation
Acinetobacter baumannii Start ampicillin/sulbactam
Bacteroides fragilis Start metronidazole
If polymicrobial infection, piperacillin/tazobactam, ampicillin/sulbactam, or meropenem based on other organisms
Do NOT double cover anaerobes
Citrobacter spp. Start/continue cefepime
Cronobacter sakazakii Start/continue cefepime
Enterobacter (non-cloacae complex) Start/continue cefepime
Enterobacter cloacae complex Start/continue cefepime
Escherichia coli Continue empiric coverage and await susceptibilities
Fusobacterium nucleatum
Fusobacterium necrophorum		 Start ampicillin/sulbactam or start/continue metronidazole
Haemophilus influenzae Start/continue ceftriaxone
Klebsiella oxytoca Continue empiric coverage and await susceptibilities
Klebsiella pneumoniae group Continue empiric coverage and await susceptibilities
Morganella morganii Start/continue cefepime
Neisseria meningitidis Continue empiric coverage and await susceptibilities
Proteus spp.
Proteus mirabilis		 Continue empiric coverage and await susceptib
Pseudomonas aeruginosa Start/continue cefepime or piperacillin-tazobactam
Salmonella spp Start/continue ceftriaxone
Serratia spp.
Serratia marcescens		 Start/continue cefepime
Stenotrophomonas maltophilia Start trimethoprim-sulfamethoxazole (15-20mg/kg/day divided q8h for normal renal function)
Gram-Negative Resistance Genes
CTX-M Positive (ESBL)
  • Start meropenem
  • Consider an Infectious Diseases consult
  • Contact precautions (see Infection Prevention website)
IMP Positive
KPC Positive
NDM Positive
OXA (OXA-23 and OXA-48) Positive
VIM Positive
  • Carbapenemase-producing organism
  • Obtain Infectious Disease consultation
  • Contact precautions (see Infection Prevention website)
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