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Listeria monocytogenes CNS infection treatment meropenem
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Listeria monocytogenes meningitis treatment ampicillin
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Clinical Analysis: 60-Year-Old Female, Neurosurgery ICU
Patient Snapshot
- Mrs. Chandaben Vasudevbhai Rathod, 60 years, Female
- Diagnosis: Hydrocephalus + Left gangliocapsular (GC) region intraparenchymal hemorrhage
- Unit: Neurosurgery ICU, SVPIMSR
- Specimen: CSF from Ommaya shunt (26 May 2026)
Lab Results Summary
CSF Cytology / Appearance (Image 2)
| Parameter | Result | Interpretation |
|---|---|---|
| Colour | Colourless | Normal appearance |
| Appearance | Clear | No turbidity |
| Blood | Absent | |
| Cobweb | Absent | Against TB |
| Total Cell Count | 15 cells/mm³ | Mild pleocytosis |
| Polymorphs | 20% | |
| Lymphocytes | 80% | Lymphocytic predominance |
| RBCs | Few |
CSF Biochemistry (Image 3)
| Parameter | Result | Reference | Interpretation |
|---|---|---|---|
| CSF Sugar | 122 mg/dL | 40-70 | Elevated - unusual |
| CSF Protein | 35.6 mg/dL | 8-32 | Mildly elevated |
Microbiology (Image 1)
| Test | Result |
|---|---|
| Gram Stain | Gram positive bacilli seen |
| ZN Stain | Acid fast bacilli NOT seen |
| Culture (48h) | Scanty growth - Listeria monocytogenes |
| Benzylpenicillin | Susceptible |
| Trimethoprim/Sulfa | Susceptible |
| Meropenem | Sensitive (MIC 0.25) |
Key Clinical Interpretation
This is Listeria monocytogenes CNS infection (meningitis/ventriculitis) via the Ommaya shunt - a device-associated CNS infection in a 60-year-old woman with hydrocephalus and intraparenchymal hemorrhage.
Why this CSF pattern is classic for Listeria:
- Gram-positive bacilli on smear (seen in only ~30% of cases - confirmed here)
- Lymphocytic predominance (80%) - occurs in ~30% of Listeria CNS cases, mimicking aseptic meningitis; most bacterial meningitides show neutrophilic pleocytosis
- Mildly elevated protein
- Elevated CSF glucose (unlike TB or cryptococcal meningitis where glucose drops)
- Age >50 years is a classic risk group
Treatment Guidance
Drug of choice: Ampicillin (both susceptible results confirm this)
Per Goldman-Cecil Medicine: "For confirmed cases of listeriosis, ampicillin (2 grams IV every 4 hours) is generally the drug of choice. In cases of meningitis... gentamicin is usually added to ampicillin." Duration: minimum 3 weeks for CNS involvement.
| Antibiotic | Recommendation |
|---|---|
| Ampicillin 2g IV q4h | First-line - drug of choice |
| + Gentamicin | Add if meningitis/encephalitis (synergy); caution with renal function |
| TMP/SMX | Alternative if penicillin allergy (5 mg/kg TMP component IV q6-8h) |
| Meropenem | Sensitive (MIC 0.25) - usable as salvage/if ampicillin not tolerated |
| Avoid cephalosporins | Inherently resistant (e.g., ceftriaxone NOT active against Listeria) |
| Avoid vancomycin | Not effective even if in vitro susceptibility shown |
Note on meropenem sensitivity here: While meropenem shows sensitivity (MIC 0.25), it is NOT the preferred agent. Ampicillin remains the standard of care. Meropenem may be considered in refractory cases or when ampicillin is contraindicated.
Clinical Concerns & Recommendations
- Source control: Ommaya shunt is a foreign body - evaluate whether the shunt needs removal or revision, as device-associated Listeria infections are difficult to eradicate without hardware removal.
- Duration: Given CNS involvement with hydrocephalus + Ommaya shunt, treat for at least 3-6 weeks (some references cite 6 weeks for brain abscess/device infections).
- Immunocompromise workup: Age 60, ICU patient with intraparenchymal hemorrhage - check if on corticosteroids (common post-neurosurgery), which is a known predisposing factor.
- Gentamicin addition: Strongly consider adding gentamicin (adjust for renal function) given CNS/meningitic involvement and device infection.
- Repeat CSF cultures post-therapy initiation to confirm clearance.
Sources: Goldman-Cecil Medicine (International Edition) - Listeriosis Treatment section; Rosen's Emergency Medicine - Impaired Cell-Mediated Immunity; Adams and Victor's Principles of Neurology
Create a quick antibiotic dosing reference for Listeria CNS management
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Valid DOCX file. Here is your reference card:
Listeria CNS Dosing Reference
Word Document · DOCX
The document includes 6 colour-coded sections:
1. Critical Principles (red alert box)
- Cephalosporins are NOT active against Listeria
- Vancomycin is NOT effective (even with in vitro susceptibility)
- Ampicillin is drug of choice
2. Antibiotic Regimen Table
| Drug | Dose | Frequency |
|---|---|---|
| Ampicillin (1st line) | 2 g IV | q4h |
| + Gentamicin (synergy) | 2 mg/kg load → 1.7 mg/kg IV | q8h (renally adjusted) |
| Gentamicin intraventricular (Ommaya) | 5 mg preservative-free | Once daily via shunt |
| TMP/SMX (PCN allergy) | 5 mg/kg (TMP) IV | q6-8h |
| Meropenem (salvage) | 2 g IV | q8h |
3. Duration by Syndrome - bacteremia (2 wk) → meningitis (≥3 wk) → brain abscess/endocarditis (≥6 wk) → Ommaya shunt infection (4-6 wk retained, ≥3 wk post-removal)
4. Special Situations - Ommaya shunt management, renal adjustment, penicillin allergy, immunocompromised patients, iron withholding
5. Monitoring parameters - gentamicin levels, renal function, repeat CSF cultures
6. CSF Pattern diagnostic clues - including the lymphocytic predominance trap and why normal glucose does not exclude Listeria
Sources: Goldman-Cecil Medicine, Goodman & Gilman's Pharmacology, Rosen's Emergency Medicine, Adams & Victor's Neurology
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