CNS Infections - MCBY PDF

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Microbiology and CNS Infections ...

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[ CNS INFECTIONS ] LIST 

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Acute meningitis o Polymorphonuclear – bacterial o Lymphocytic – viral Encephalitis/ myelitis Brain abscess, subdural and epidural collections

MENINGITIS 

Meningeal inflammation o Meningism  [fever, headache, photophobia] – NOT confirmed meningitis

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GENERAL POINTS o BACTERAEMIA  Organisms in blood stream  Can have minimal symptoms o SEPTICAEMIA  Bacteraemia with a high sepsis score  Fever  Tachycardia  Shock  Coagulopathy organ failure o PYAEMIA  Metastatic foci  Bad prognosis

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CSF FINDINGS  BACTERIAL VIRAL

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CELLS Polymorphs Lymphocytes

PROTEIN Raised Raised

GLUCOSE Low Normal

TYPES o VIRAL (LYMPHOCYTIC) MENINGITIS  Viral  Enteroviruses – Coxsackie, ECHO, (Poliomyelitis)  Mumps (making a comeback due to poor herd immunity) 

Bacterial  Partially treated  Tuberculosis, Lyme disease  Syphilis, Encephalitis  SLE

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Needs analgesia and reassurance

o BACTERIAL (POLYMORPHONUCLEAR) MENINGITIS  Bacteria (in order of incidence)  Streptococcus pneumoniae (pneumococci) o Gram positive diplococcus o Major primary opportunistic pathogen o Common cause of meningitis now o Polysaccharide capsules – effective against phagocytosis and is immunogenic o Penicillin resistance not usual in UK, influences morbidity in meningitis (cefotaxime), NOT pneumonia o Disease of adults (+ alcohol, socially marginalised) o Common features - cerebral oedema (encephalopathic features) 

Neisseria meningitidis (meningococci) o Gram-negative diplococcus o 12 capsular serotypes  B – commonest (no vaccine)  C – next common (vaccine)  A – African – vaccine  ETC – W,Y, 135 o Commonest in children o Commensal neisseriae – gives protective immunity o Preadmission penicillin

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Haemophilus influenzae group B (Hib) All others can also lead to it

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Meningococcal infection o Vaccine introduced 1999 – decreased incidence

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Public health measures o CLOSE contact – same roof  Family, flatmates, kissing

o Antibiotics  Single dose CIPROFLOXACIN  48 hours RIFAMPICIN  Single dose CEFTRIAXONE o Vaccine booster – if appropriate

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Haemophilus meningitis  Gram-negative bacillus – penicillin resistant - CEFOTAXIME  Get focal neurological signs

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Other causes of bacterial meningitis  Collection  Brain abscess  Parameningeal collection  Early viral  Listeria (immunosuppressed, neonates)  Staphylococci (CSF shunts)  Group B streptococci (neonates)  Enterobacteria (neonates)

MANAGEMENT o HISTORY  Meningism – fever, headache, photophobia  Neurology – fits, consciousness  Epidemiology – contacts, travel, immunisation o EXAMINATION  Rash  Blanching – viral  Non-blanching – bacterial  Meningism – Kering’s  Neurological – focal signs  Sepsis – tachycardia, hypotension

o MENINGITIS TREATMENT  Antimicrobials  Beta lactams o Penicillin (not haemophilus) o Cefotaxime (better penetration )

 Steroids (dexamethasone)  Cerebral oedema o Focal neuro signs o CT

 Sepsis  Fluid resuscitation  Intensivists  Analgesia  Especially viral meningitis  Analgesic effect of explanation and reassurance

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INVESTIGATIONS o BLOODS  Blood culture  WBC  Renal – fever, headache, photophobia, renal o RADIOLOGY  CT – before lumbar puncture – to rule out intracranial pressure  Can see collections and cerebral oedema o LUMBAR PUNCTURE  Cells – red cells, polymorphs, lymphocytes, others  Chemistry – glucose, protein, immunoglobulins  Culture  Immunoassay  PCR

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TAKE AWAY POINTS o Most likely viral – then pneumococcal o Viral meningitis can have rash o Severe sepsis can have purpuric rash o Rarer with immunisation o Preadmission penicillin to be carried – for rapid onset/ non-blanching o Importance of imaging – ICP, other pathologies

ENCEPHALITIS  

Parenchymal brain inflammation  focal neurological signs Causes – viruses (dengue, poliovirus, Coxsackie, herpes simplex I and II, HIV), bacteria, others, etc.

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VIRAL ENCEPHALITIS o CAUSES – herpes simplex o DIAGNOSIS – acute change in brain function (seizures, impaired conscious level, cognitive impairment, focal signs), underlying disease, CSF changes (not as diagnostic) – raised protein IgG, organisms (culture, PCR of herpes, Immunoassay)

o IMAGING – MRI scan o TREATMENT – herpes simples (acyclovir, high dose, parenteral), bacterial (as appropriate)

MYELITIS 

Spinal cord inflammation  referred symptoms along dermatome

HYBRID TERMS  

Meningoencephalitis Encephalomyelitis...