Culture & Sensitivity, Aerobic bacteria CSF (Manual method)

Bacterial/ Viral

Report in 72Hrs

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No Fasting Required

Details

It helps identify the causative organism of meningitis, encephalitis, or brain abscess, and determine effective antibiotics

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Culture & Sensitivity Aerobic bacteria CSF (Manual method)

Why is it done?
- To identify and isolate aerobic bacterial pathogens present in cerebrospinal fluid (CSF) samples
- To diagnose bacterial meningitis, ventriculitis, and other CNS infections
- To perform antimicrobial susceptibility testing for appropriate antibiotic therapy selection
- Ordered when patients present with clinical signs of meningitis: fever, headache, neck stiffness, altered mental status, and photophobia
- Performed emergently in suspected CNS infections to guide immediate therapeutic interventions
- Used in post-neurosurgical patients to detect infections following invasive procedures or shunt placement
Normal Range
- Normal Result: No growth of aerobic bacteria or negative culture
- Units of Measurement: Colony Forming Units (CFU/mL) or presence/absence notation
- Reference Range: CSF is normally sterile with no bacterial growth after 24-72 hours of incubation
- Negative Culture: No bacterial pathogens isolated; normal finding consistent with sterile CNS
- Positive Culture: Any bacterial growth is abnormal and indicates active CNS infection
- Interpretation Note: Even single colonies may represent significant infection given the normally sterile nature of CSF
Interpretation
- Positive Culture - Bacterial Identification: Confirms bacterial meningitis; identified organism guides definitive antibiotic therapy. Common pathogens include Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae, Listeria monocytogenes
- Antimicrobial Susceptibility Results: Reports testing against multiple antibiotics with interpretations: Susceptible (S), Intermediate (I), or Resistant (R). Guides selection of most effective antimicrobial therapy
- Negative Culture: Suggests absence of aerobic bacterial infection; may indicate viral meningitis, fungal infection, tuberculosis, or other non-bacterial etiologies. Does not rule out infection if clinical suspicion remains high
- Contamination Considerations: Growth of common skin flora (Staphylococcus epidermidis, Propionibacterium) typically represents contamination but must be differentiated from true infection in post-surgical patients
- Factors Affecting Results: Prior antibiotic therapy may reduce culture positivity; timing of LP relative to symptom onset; sample contamination during collection; sample volume adequacy; proper handling and transport
- Clinical Significance: Positive culture is diagnostic for bacterial meningitis and requires immediate hospital admission, isolation precautions, and targeted antibiotic therapy. Negative culture does not exclude bacterial infection, especially if obtained after initiation of antibiotics
Associated Organs
- Primary Organ Systems: Central nervous system (CNS) - brain, spinal cord, meninges; cerebrospinal fluid compartment
- Bacterial Meningitis: Inflammation of the pia mater and arachnoid membrane; life-threatening infection with high mortality (15-20%) if untreated; potential complications include subdural empyema, ventriculitis, hydrocephalus
- Associated CNS Conditions: Ventriculitis (infection of ventricular system); subdural empyema; epidural abscess; brain abscess; cerebritis; spinal cord infection
- Potential Complications: Permanent neurological damage (hearing loss, cognitive impairment, motor deficits); septic shock; disseminated intravascular coagulation (DIC); seizures; coma; death
- Associated Risk Factors: Neurosurgical procedures, lumbar puncture, shunt placement, head trauma, immunocompromised states, asplenia, complement deficiency
- Secondary Organ Involvement: May spread to blood (septicemia), cardiovascular system (septic shock), kidneys (acute renal failure), and other organs in severe cases
Follow-up Tests
- If Culture is Positive: Blood cultures (identify concurrent bacteremia); CT/MRI of brain (detect complications); follow-up LP to assess treatment response; repeat CSF analysis; audiological evaluation (for meningitis sequelae)
- Complementary CSF Studies: CSF Gram stain; CSF cell count and differential; CSF protein and glucose; CSF lactate; viral PCR panels if culture negative but meningitis suspected
- If Culture is Negative but Meningitis Suspected: Molecular testing for common bacteria and viruses; fungal and mycobacterial cultures if appropriate; repeat LP if clinical deterioration; imaging studies; PCR panels for viral etiologies
- Monitoring and Follow-up: Serial clinical assessments; repeat CSF cultures if initial therapy fails; neurological examinations for complications; audiometry and developmental screening in pediatric cases
- Imaging Studies: MRI or CT of brain/spine to evaluate for ventriculitis, subdural collections, hydrocephalus, or abscess formation
- Repeat Testing Indications: Clinical failure after 48-72 hours of appropriate therapy; suspected shunt-related infection; immunocompromised patients with inadequate response; suspected fungal or tuberculous infection
Fasting Required?
- Fasting: No - fasting is not required for CSF culture collection
- Patient Preparation: Standard informed consent required; patient positioned for lumbar puncture (LP) - typically lateral decubitus position; cleansing of lumbar puncture site with antiseptic solution
- Medications: No specific medication restrictions; empiric antibiotics may be started before LP if meningitis suspected; anticoagulation should be addressed if significant (hold warfarin, assess bleeding risk with antiplatelet agents)
- Special Instructions: Sample must be collected in sterile container during lumbar puncture; minimum 1-2 mL recommended for culture; immediate transport to laboratory at room temperature or 37°C within 30 minutes of collection to prevent bacterial overgrowth or death
- Contraindications to LP: Significant thrombocytopenia (<50,000/μL), severe coagulopathy, anticoagulation therapy, signs of increased intracranial pressure with mass effect on imaging, skin infection at puncture site
- Sample Labeling: Must be clearly labeled as CSF with patient identification, date, time of collection, and indication; proper chain of custody documentation

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