Microbiology Induction for
Neurosurgery trainees
Kavita Sethi
Consultant Microbiologist
LTHT
LTHT Microbiology
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
LEEDS HEALTH PATHWAYS
 Neurosurgery, Neurology, Rehabilitation Medicine
Specialty Specific Treatment
 Brain abscess and subdural empyema
 Deep spinal infection in adults
 Herpes Simplex Encephalitis in adults
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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
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)
How do you evaluate infection
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.
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)
Total white cell count and C-reactive protein
surgery
30
250
WBC
200
CRP
20
150
15
100
10
5
50
0
0
-6
-4
-2
0
2
4
Day
6
8
10
12
CRP (mg/L)
WBC (x 109 /L)
25
Risk Factors
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Admission for more than 48 hours
Mechanical ventilation
Trauma
Vascular catheterisation
Urinary catheterisation
Stress ulcer prophylaxis
EPIC 1995
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
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
Pathogenesis
 What is on the skin goes in the wound
 Most cases are a result of surgical wound infection
 Independent risk factors :
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GCS < 10
Emergency surgery
CSF leakage
External CSF drainage
Diagnosis of bacterial meningitis post-neurosurgery
Useful criteria
Less helpful criteria
high fever
new neurological deficit
active CSF leak
CSF leukocytosis
blood leukocytosis
CSF glucose
CSF protein
type of operation
presence of foreign material
steroid use
altered mental status
neck stiffness
headache / nausea
Ross et al. Journal of Neurosurgery 1988; 69: 669-74
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
CSF Penetration of antibiotics
 Excellent
 Useless
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 Macrolides
 Aminoglycosides
 Clindamycin
Ceftazidime
Meropenem
Metronidazole
Rifampicin
Chloramphenicol
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
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
Empiric therapy
1st line therapy
Cefotaxime
2-3g qds
Confirmed
P.aeruginosa or recent
broad spectrum
antibiotic
Ceftazidime
2g tds
Suspected or
confirmed ESBLproducing
Enterobacteriaceae or
Acinetobacter spp.
Meropenem
2g tds
MSSA
Flucloxacillin
2-3g qds
MRSA
Vancomycin PLUS
Rifampicin
1g bd
600mg bd
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) p=0.68
CSF leakage subset RR 1.34 (0.75 - 2.41) p=0.36
Brain abscess
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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 <5%
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Overall mortality rate has ranged from 0% to 24%.
Prognosis
the rapidity of progression before hospitalization
mental status onadmission
Bacteriology
􀁺 Streptococci (70%)
􀁺mixed infections (30% to 60%)
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􀁺 Streptococcus milleri group
􀁺 oral cavity, appendix, and female genital tract
􀁺 otopharyngeal infections ,
􀁺 IE
􀁺Staphylococcus aureus 10% to 15%
 􀁺 cranial trauma
 􀁺 IE

Neurosurgical procedure
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
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.
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
Initial approach to the patient with
a 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 > 2.5 cm in diameter should be excised or
stereotactically aspirated.
 􀁺 For abscesses in the early cerebritis stage or when the abscesses
are < 2.5 cm in diameter, the largest lesionshould be aspirated for
diagnosis and organism identification
Antimicrobial therapy
 empirical antimicrobial therapy should be initiated on the basis of the
patient’s predisposing conditions and the presumed
pathogenesis of abscess formation
Otitis media/mastoiditis/sinusitis Cefotaxime/ Metronidazole
Post neurosurgical /trauma add anti-staphylococcal cover
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Use Ceftazidime as the 3rd generation cephalosporin if
Pseudomonas aeruginosa is suspected
Brain Abscess - Surgical treatment
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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.
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
Clinical features
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Variable
Fever
Signs of raised ICP
Evidence of shunt malfunction
Distal shunt infections can present with peritonitis
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
Clinical Suspicion of VP Shunt Infection
CSF Gram Strain & Culture
Mild Ventriculitis
Severe Ventriculitis
and wound infection
Await Cultures
as gram stain
usually negative
POSITIVE
Gram Positive
IT VAN
IV antibiotics
and drainage of
pus with shunt
removal
SHUNT
REMOVAL AND
EVD
Gram Negative
*IVCTX + IT GEN
*MER if any
risk factors for resistant GNBs
Consult Microbiology to
discuss alternatives if
documented Penicillin
allergy or multi-resistant
gram negative organism.
Repeat CSF in 48-72 Hours
Monitor Response
Shunt replacement when CSF sterile at the end of therapy
(see duration of antibiotics under treatment section)
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)
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
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
Hand Hygiene