Leuconostoc / Pediococcus spp.
Gram-positive cocci in pairs, chains or tetrads
Identification & Growth
Identification
- Catalase-negative; Leuconostoc produces gas from glucose, Pediococcus does not
- LAP and PYR help to separate them from Enterococcus and streptococci
Growth Conditions
- Blood agar, 35 °C, enriched atmosphere, 24–48 h
Clinical Significance
- Catheter-related bacteremia, enteral nutrition and prolonged vancomycin use
Intrinsic Resistance
- Intrinsic vancomycin resistance (EUCAST expected phenotype) — do not report glycopeptides
Bench Alerts
- Vancomycin-resistant, catalase-negative Gram-positive cocci: consider this group before VRE
Clinical Notes
Clinical presentations
- Causes opportunistic bacteremia, mainly in immunocompromised patients and preterm neonates.
- May be associated with catheter-related infections and intestinal translocation.
- Meningitis and abscess cases are rare but described in the literature.
Specimens and collection
- Blood culture is the primary specimen for bacteremia diagnosis; standard incubation is generally sufficient.
- Catheter tip should be cultured when device-related infection is suspected.
- Clinical correlation is essential, as the organism can be a contaminant from dairy/food-related handling of samples.
Epidemiology and at-risk populations
- Found in fermented dairy products and as a transient colonizer of the gastrointestinal tract.
- Oncology, neutropenic patients, and those on total parenteral nutrition have increased bacteremia risk.
- Prior vancomycin use is a relevant risk factor due to the organism's intrinsic resistance.
Resistance and therapeutic implications
- Both genera have intrinsic vancomycin resistance, making this agent unsuitable for empiric treatment.
- Ampicillin and penicillin generally retain activity and are preferred when susceptibility is confirmed.
- Prior inappropriate empiric vancomycin use in Gram-positive coccal bacteremia should raise suspicion for this organism.
Bench and reporting notes
- Intrinsic vancomycin resistance in a catalase-negative Gram-positive organism should raise suspicion for Leuconostoc or Pediococcus rather than VRE.
- MALDI-TOF is the preferred identification method, as automated biochemical panels can misidentify these as streptococci.
- Report should explicitly highlight intrinsic vancomycin resistance to prevent inappropriate therapy.
Sources
- PubMed — Leuconostoc and Pediococcus infections review
- EUCAST — Clinical breakpoints
- CDC — Vancomycin-resistant organisms
Educational decision-support content. It does not replace laboratory validation, current guidelines or review by the responsible professional.
FAQ: Frequently Asked Questions
How to identify Leuconostoc / Pediococcus spp. in the lab?
Leuconostoc / Pediococcus spp. is identified through catalase-negative; leuconostoc produces gas from glucose, pediococcus does not, lap and pyr help to separate them from enterococcus and streptococci.
What are the intrinsic resistances of Leuconostoc / Pediococcus spp.?
This organism is naturally resistant to intrinsic vancomycin resistance (eucast expected phenotype) — do not report glycopeptides. These drugs should not be reported as susceptible.
Where is Leuconostoc / Pediococcus spp. commonly found?
It is typically associated with catheter-related bacteremia, enteral nutrition and prolonged vancomycin use.
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