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 infx, no need to repeat (most other strep and GNR’s)
- VUMC 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 |
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 (e.g. 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 complex |
| Escherichia coli | Continue empiric coverage and await sensitivities |
| Fusobacterium nucleatum Fusobacterium necrophrum |
Start ampicillin/sulbactam or start/continue metronidazole |
| Haemophilus influenzae | Start/continue ceftriaxone |
| Klebsiella oxytoca | Continue empiric coverage and await sensitivities |
| Klebsiella pneumoniae group | Continue empiric coverage and await sensitivities |
| Morganella morganii | Start/continue cefepime |
| Neisseria meningitidis | Continue empiric coverage and await sensitivities |
| Proteus spp. Proteus mirabilis |
Continue empiric coverage and await sensitivities |
| Pseudomonas aeruginosa | Start/continue cefepime or piperacillin-tazobactam |
| Salmonella spp | Start/continue ceftriaxone |
| Serratia spp. Serratia marcescens |
Start/continue cefepime |
| Stenotrophomonas maltophiolia | 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) |