Microbiology Induction for Neurosurgery trainees Kavita Sethi Consultant Microbiologist LTHT.

Microbiology Induction for Neurosurgery trainees

Kavita Sethi

Consultant Microbiologist

LTHT

LTHT Microbiology

Contact Details

Duty Microbiologist for 0113-392-3962 or -8580

interpretative amp clinical advice

Ext 25034 if need to contact myself

(Contact via switchboard for urgent queries)

For laboratory assistance within normal working hours (eg

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 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 (ge 16 years of age

Restricted Antimicrobial Policy

bull To slow the development of resistance to a drug by limiting its use

bull 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)

0

5

10

15

20

25

30

-6 -4 -2 0 2 4 6 8 10 12Day

WB

C (

x 10

9 L

)

0

50

100

150

200

250

CR

P

(mg

L)

WBC

CRP

surgery

Total white cell count and C-reactive protein

Risk Factors

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 Pacnes Staphylococcus aureus

Postoperative bacterial meningitis

Low overall incidence Variables

Clean or clean-contaminated Antibiotic prophylaxis

Aetiology Aerobic GNB (60-70)

Ecoli Kpneumoniae Paeruginosa Acinetobacter spp Saureus Spneumoniae (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 GCS lt 10 Emergency surgery CSF leakage External CSF drainage

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

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 Ceftazidime Meropenem Metronidazole Rifampicin Chloramphenicol

Useless Macrolides Aminoglycosides Clindamycin

Additional points

Duration of therapy Saureus ndash 2 weeks AGNB ndash 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 amp CSF cell count and chemistry) CSF lactate to distinguish

Approach Empirical antibiotic therapy If CSF sterile ndash discontinue antibiotics Responds favourably to high dose corticosteroids

Empiric therapy

1st line therapy Cefotaxime 2-3g qds

Confirmed Paeruginosa or recent broad spectrum antibiotic

Ceftazidime 2g tds

Suspected or confirmed ESBL-producing 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 115 (068 - 194) p=068

CSF leakage subset RR 134 (075 - 241) p=036

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

Bacteriology

1048698 Streptococci (70)1048698mixed infections (30 to 60) 1048698 Streptococcus milleri group 1048698 oral cavity appendix and female genital tract 1048698 otopharyngeal infections 1048698 IE

1048698Staphylococcus aureus 10 to 15 1048698 cranial trauma 1048698 IE Neurosurgical procedure

Contd

Bacteroides and Prevotella in 20 to 40 1048698 mixed infection Enteric gram-negative bacilli (Proteus species

Escherichia coli Klebsiella and Pseudomonas) in 23 to 33

1048698 otitic infection 1048698 Septicemia 1048698 neurosurgical procedures 1048698 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 ndash (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 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 1048698 All lesions gt 25 cm in diameter should be excised or

stereotactically aspirated 1048698 For abscesses in the early cerebritis stage or when the

abscesses are lt 25 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 patientrsquos predisposing conditions and the presumed

pathogenesis of abscess formation

Otitis mediamastoiditissinusitis Cefotaxime Metronidazole

Post neurosurgical trauma add anti-staphylococcal cover

Use Ceftazidime as the 3rd generation cephalosporin if Pseudomonas aeruginosa is suspected

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

Shunt infections

CSF shunts become infected by various routesbull Organisms directly colonize the shunt usually at the time of surgerybull Organisms reach the CSF and the shunt via haematogenous spreadbull 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

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

Mild Ventriculitis Severe Ventriculitis and wound infection

POSITIVE Gram Positive Gram Negative MER if any risk factors for resistant GNBs

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)

Consult Microbiology to discuss alternatives if documented Penicillin allergy or multi-resistant gram negative organism

IVCTX + IT GEN

SHUNT REMOVAL AND EVD

IT VAN

CSF Gram Strain amp Culture

Await Cultures as gram stain usually negative

IV antibiotics and drainage of pus with shunt removal

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 symptomsand signs of ventriculitis

CSF sample

+ Gram stain or+ culture

- Gram stain and culture

2nd sample

+ Gram stain or + culture (sameAs 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