Microbiology Induction for Neurosurgery trainees

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Microbiology Induction for Neurosurgery trainees

• Kavita Sethi
• Consultant Microbiologist
• LTHT

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LTHT Microbiology
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Contact Details

• Duty Microbiologist for 
  0113-392-3962 or -8580
• interpretative clinical advice
• Ext 25034 if need to contact myself
• (Contact via switchboard for urgent queries)
• For laboratory assistance within normal working
  hours (e.g. urgent samples) 0113-392-3499
• Results will NOT normally be given out by
  telephone if the result is already available on
  the results server

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LEEDS HEALTH PATHWAYS

• Neurosurgery, Neurology, Rehabilitation
  MedicineSpecialty Specific Treatment
• Brain abscess and subdural empyema
• Deep spinal infection in adults  
• Herpes Simplex Encephalitis in adults  
• GeneralTreatment
• Clostridium Difficile Infection
• Community Acquired Pneumonia
• Hospital Acquired Pneumonia (Non-ventilated
  Patients) 
• Severe Sepsis Screening Tool and Resuscitation
  Care Bundle (Adults) 
• Urinary Tract Infections (UTIs) including acute
  pyelonephritis in Adults ( 16 years of age

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Restricted Antimicrobial Policy

• To slow the development of resistance to a drug
  by limiting its use
• There are more suitable alternatives that are
  less expensive or less toxic
• DOCUMENTED approval from one of the Medical
  Microbiologists or infectious diseases physicians
  prior to prescribing (antimicrobial code)

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How do you evaluate infection
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NORMOTHERMIA

• An increase in body and brain temperature is
  associated with an increase in CBF, cerebral
  metabolic requirement for oxygen and oxygen
  utilisation, resulting in an increase in ICP and
  further cerebral ischaemia.
• Pharmacological antipyretics and surface cooling.

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Evaluation of fever in Neurosurgical patients

• Nervous system is a sterile milieu.
• Fever occurs in 25 of neurocritical care
  patients with 50 being noninfectious
• Hypothalamic temp.
• Majority of infections within the Neurocritical
  care units are nosocomial (device related
  infections)

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Total white cell count and C-reactive protein
surgery
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Risk Factors

• Admission for more than 48 hours
• Mechanical ventilation
• Trauma
• Vascular catheterisation
• Urinary catheterisation
• Stress ulcer prophylaxis

EPIC 1995
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Nosocomial infections on NITU

• Respiratory infection
• Early
• Late
• Bacteremia
• GI infection
• UTIs
• Neurosurgical device related infections

• Haemophilus influenzae, Staphylococcus aureus,
  Streptococcus pneumoniae
• Pseudomonas, Coliforms, Acinetobacter, MRSA
• Clostridium difficile
• Asymptomatic bacteruria in catheterised patients
• Coagulase negative Staphylococcus, P.acnes,
  Staphylococcus aureus

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Postoperative bacterial meningitis

• Low overall incidence
• Variables
• Clean or clean-contaminated
• Antibiotic prophylaxis
• Aetiology
• Aerobic GNB (60-70)
• E.coli, K.pneumoniae, P.aeruginosa, Acinetobacter
  spp.
• S.aureus
• S.pneumoniae (dural defects/ CSF otorrhoea or
  rhinorrhoea)
• REMEMBER ASEPTIC MENINGITIS

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Pathogenesis

• What is on the skin goes in the wound
• Most cases are a result of surgical wound
  infection
• Independent risk factors
• GCS lt 10
• Emergency surgery
• CSF leakage
• External CSF drainage

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Diagnosis of bacterial meningitis
post-neurosurgery

• Useful criteria Less helpful criteria
• high fever CSF glucose
• new neurological deficit CSF protein
• active CSF leak type of operation
• CSF leukocytosis presence of foreign material
• blood leukocytosis steroid use
• altered mental status
• neck stiffness
• headache / nausea

Ross et al. Journal of Neurosurgery 1988 69
669-74
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Diagnosis of Nosocomial meningitis

• Challenging
• Clinical
• Indistinguishable from community-acquired
  meningitis
• May be difficult to distinguish from neurological
  signs/ symptoms of underlying disease or
  associated with post-op period
• LP must be performed to confirm diagnosis (CT
  first to establish safety)
• CSF parameters may be altered due to surgery
  itself especially in the presence of SAH
• CSF leucocytosis not infrequent
• Antibiotics which achieve adequate CSF levels
  (guided by gram stain and culture)
• Surgical management of wound infection/
  persistent CSF leak

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CSF Penetration of antibiotics

• Excellent
• Ceftazidime
• Meropenem
• Metronidazole
• Rifampicin
• Chloramphenicol

• Useless
• Macrolides
• Aminoglycosides
• Clindamycin

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Additional points

• Duration of therapy
• S.aureus 2 weeks
• AGNB up to 3 weeks
• Vancomycin penetrates poorly into CSF and patient
  may fail to respond to systemic therapy
• Implant an Ommaya reservoir and instill
  vancomycin directly into ventricles every 3rd day

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Postoperative aseptic meningitis

• Thought to be the result of irritation caused
  either by blood/ degradation products introduced
  into SAS during surgery
• Indistinguishable from postoperative bacterial
  meningitis (clinical CSF cell count and
  chemistry)
• ? CSF lactate to distinguish
• Approach
• Empirical antibiotic therapy
• If CSF sterile discontinue antibiotics
• Responds favourably to high dose corticosteroids

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Empiric therapy
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Antibiotic Prophylaxis for Basilar Skull
Fracture? Meta Analysis

• 12 studies, 1241 patients
• 58 received antibiotics
• Antibiotics did not prevent meningitis RR 1.15
  (0.68 - 1.94) p0.68
• CSF leakage subset RR 1.34 (0.75 - 2.41) p0.36

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Brain abscess

• Hematogenous spread from extracranial site
• Can arise from direct spread from mastoid and
  sinus infections
• Corticomedullary junction
• Frontal and parietal lobes most common
• Posterior fossa lt5
• Overall mortality rate has ranged from 0 to 24.
• Prognosis
• the rapidity of progression before
  hospitalization
• mental status onadmission

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Bacteriology

• ?? Streptococci (70)
• ??mixed infections (30 to 60)
• ?? Streptococcus milleri group
• ?? oral cavity, appendix, and female genital
  tract
• ?? otopharyngeal infections ,
• ?? IE
• ??Staphylococcus aureus 10 to 15
• ?? cranial trauma
• ?? IE
• Neurosurgical procedure

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Contd.

• Bacteroides and Prevotella in 20 to 40
• ?? mixed infection
• Enteric gram-negative bacilli (Proteus species,
  Escherichia coli, Klebsiella and Pseudomonas) in
  23 to 33
• ?? otitic infection
• ?? Septicemia
• ?? neurosurgical procedures
• ?? immunocompromised
• Rare pathogens Nocardia, Mycobacterium
  tuberculosis, Listeria monocytogenes

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Brain abscess

• Blood cultures should be obtained when diagnosis
  is suspected
• Lumbar puncture (LP) should be deferred in any
  case for which brain abscess is suspected because
  of the potential for CNS herniation and low
  likelihood of positive cultures.
• Pus collected in a sterile universal container
  (NOT SWAB) should be sent to Microbiology for
  urgent microscopy, culture and sensitivity.

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Cerebritis and abscess

• Early cerebritis (3-5 days)
• Late Cerebritis -(4 to 14 days)
• Early Capsule Stage (Begins at 2 weeks following
  initial infection)
• Late capsule stage

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Initial approach to the patient witha suspected
brain abscess

• Contrast CT or MRI should be performed
• If single or multiple ring-enhancing lesions are
  found, the patient should taken urgently to
  surgery.
• ?? All lesions gt 2.5 cm in diameter should be
  excised or stereotactically aspirated.
• ?? For abscesses in the early cerebritis stage or
  when the abscesses are lt 2.5 cm in diameter, the
  largest lesionshould be aspirated for diagnosis
  and organism identification

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Antimicrobial therapy

• empirical antimicrobial therapy should be
  initiated on the basis of the patients
  predisposing conditions and the presumed
• pathogenesis of abscess formation
• Otitis media/mastoiditis/sinusitis
  Cefotaxime/ Metronidazole
• Post neurosurgical /trauma add
  anti-staphylococcal cover
• Use Ceftazidime as the 3rd generation
  cephalosporin if Pseudomonas aeruginosa is
  suspected

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Brain Abscess - Surgical treatment

• significant mass effect exerted by lesion
• proximity to ventricle
• poor neurological condition
• Inability to obtain weekly CT scans
• In patient undergoing medical treatment
• Intervention, if neurological deterioration
  occurs, anatomic progression of abscess towards
  ventricles, or after 2 weeks of therapy if
  abscess is enlarged. Also consider if there is
  no decrease in abscess size by 4 weeks of
  treatment.

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Shunt infections

• CSF shunts become infected by various routes
• Organisms directly colonize the shunt, usually
  at the time of surgery
• Organisms reach the CSF and the shunt via
  haematogenous spread
• Organisms travel along the shunt by retrograde
  spread (uncommon)
• Coagulase-negative Staphylococci are isolated
  most commonly. Production of extracellular slime
  has been reported as being important in the
  pathogenesis of shunt infections

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Clinical features

• Variable
• Fever
• Signs of raised ICP
• Evidence of shunt malfunction
• Distal shunt infections can present with
  peritonitis

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Shunt infections

• CSF from shunt ( before antimicrobial therapy)
• SHUNT REMOVAL
• Proximal catheter, valve or shunt reservoir,
  distal catheter in three separate containers
• Intrathecal /- systemic antibiotic
• Shunt replacement once the CSF sterile

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EVD-related ventriculitis

• Incidence between 10-17
• Risk
• Lowest risk 1st 4 days that EVD is in-situ
• Rises over next 10 days
• Falls thereafter
• Incidence not decreased by exchanging EVD at
  regular intervals
• Aetiology
• CNS (predominant)

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Diagnostic approach
Patient with EVD with symptoms and signs of
ventriculitis
CSF sample
Gram stain or culture

• Gram stain
• and culture

2nd sample
Gram stain or culture (same As 1st)
Treat
No treatment
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Additional points

• Collect CSF from EVD itself or the Ommaya
  reservoir, not the drainage bag
• Treat CNS infections with intraventricular
  Vancomycin for 5-7 days
• Product license does not cover this route
• Not validated by clinical trials
• Guarantees max concentrations of vancomycin at
  the site of infection
• Avoids systemic toxicity
• Cheaper than systemic therapy
• No need to monitor levels

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Hand Hygiene