CNS Infections - Bacterial and Fungal Meningitis (27) Flashcards
CNS infections
Meningitis (bacterial, viral, TB, cryptococcus), brain abscess, encephalitis, toxin mediated
What is meningitis?
Infection of CSF/meninges
How does meningitis present?
Acute fever, headache, neck stiffness, +/- rash, fully conscious, usually viral
What is encephalitis?
Infection of brain tissue
How does encephalitis present?
Acute fever, headache, neck stiffness, altered conscious level, seizures, focal neurological signs, usually viral
What is a brain abscess?
Abscess within brain tissue
How does brain abscess present?
Insidious onset of fever, headache, +/- neck stiffness, +/- altered conscious level, seizures, focal neurological signs, usually bacterial (parasitic?)
How does invasion via micro-organisms occur?
Blood-borne invasion (blood-brain barrier/blood CSF barrier), peripheral nerves
What does normal CSF look like?
Clear
Polymorphic nucleoles likely to be
Bacterial
Neisseria meningitidis
Gram negative diplococci, require blood for growth, 13 capsular types (A, B, C, W135, Y most common), detected by nucleic acid amplification (PCR)
Natural habit of N. meningitidis
Nasopharynx, 5-20% carriers (increased smokers), half strains non-capsulate, increase in Gp A carriage rates before epidemics
Factors affecting intravascular survival (N. meningitidis)
Capsule - protects against complement-mediated bacteriolysis and phagocytosis
Acquisition of iron from transferrin
N. meningitidis BBB
Cross BBB and multiply in subarachnoid space, can remain in blood stream/not cross BBB
N. meningitidis can cause
Fulminant septicaemia, septicaemia with purpuric rash, septicaemia with meningitis, pyogenic/purulent meningitis with no rash, chronic meningococcal bacteraemia with arthralgia, focal sepsis, conjunctivitis, endophthalmitis
Is rash blanching or non-blanching?
Can be blanching early in disease and progress to be non-blanching
Treatment of N. meningitidis
Ceftriaxone, cefotaxime (Penicillin)
Chemoprophylaxis of contacts on invasive disease (N. meningitidis)
Close/kissing contacts, Rifampicin/Ciprofloxacin
Vaccination for N. meningitidis
Active against Group A and C and W135 (not against Group B)
When is peak of N. meningitidis?
Winter
Local outbreaks of N. meningitidis
Population of susceptible individuals, high transmission rate, virulent, capsulate strain
Haemophilus influenzae
Unable to grow in the absence of blood/constituents of blood, small, pleomorphic gram negative cocco-bacilli/bacilli, some strains produce a polysaccharide capsule (6 antigenic types a-f, type b causes most invasive disease)
Normal carriage of H.influenzae
Restricted to humans, 25-80% carry non-capsulate strains, 5-10% carry capsulate strains
Throat carriage of H.influenzae
Invasion of submucosa > blood stream > (invasive infections if meningitis, infants, >2 months - 2 years)
Virulence factors of H.influenzae
Type b capsule, Fimbriae, IgA proteases, outer membrane proteins/lipolysaccharide (intercurrent viral infection)
Treatment of H.influenzae
Ceftriaxone, cefotaxime (ampicillin, B-lactamase producing strains common)
Chemoprophylaxis of H.influenzae
Rifampicin
Vaccines for H.influenzae
Type b conjugates vaccines (dramatic reduction in incidence of invasive disease)
Streptococcus pneumoniae
Gram positive cocci, cells in pairs, requires blood/serum for growth, a-haemolytic activity on blood agar (green)
What test can be done to see if Step pneumoniae is present?
Optochin test (ethyldydrohupreine)
Who does Step pneumoniae effect?
All ages, more severe in elderly and immunocompromised
Treatment of Step pneumoniae
Ceftriaxone, cefotraxime (Penicillin resistance)
Vaccine for Step pneumoniae
Conjugate vaccine available against serotypes
Steroids for meningitis in adults
Must be given shortly before/with first dose of antibiotics, should be given if Step pneumoniae suspected
Neonatal meningitis usually caused by
Group B beta-haemolytic streptococci, E.coli, Listeria monocytogenes (rare)
Neonatal extent of infection (variable onset)
Early 5 days - meningitis
Treatment of neonatal meningitis
Cefotaxime (ampicillin and gentamicin)
Acute complications of meningitis
Death, overwhelming sepsis, raised ICP
Chronic complications of meningitis
Deafness, delayed development, seizures, stroke, hydrocephalus
Lymphocytic meningitis
Viral (Enterovirus/HSV 2/polio), benign outcome
Consequence of polio meningitis
Paralysis
Bacteria causing lymphocytic meningitis
Spirochete - treponemal/borrelia
Lymphocytic meningitis - TB
Insidious onset
Risk factor for TB
Immunocompromised, alcoholic, endemic area
Detection of TB
Ziehl Neelsen/Fluorescent antibody stain
Toxoplasma gondii encephalitis
Protozoan, contracted by eating contaminated meat, resembles glandular fever, immunocompromised
Cryptococcal meningitis
Lymphocytic meningitis, yeast, common with late HIV, insidious onset
Where are yeast forms of Cryptococcal meningitis seen?
In CSF in Indian Ink stain
Cryptococcal meningitis treatment
Prolonged course - amphotericin, flucytosine, fluconazole
Encephalitis
Altered conscious level, HSV 1 most common, affects temporal lobes, 50% over 50s
Diagnosis of encephalitis
Detecting viral nuclei acid in CSF (PCR)
Rabies encephalitis
Common, dog, fox, bat bites, 100% mortality, preventable by vaccination
Clostridium tetani
Gram positive spore forming bacillus, terminal round spore (drumstick), strict anaerobe
How is Clostridium tetani spread?
Contaminated soil > wound (major/minor)
Clostridium tetani’s toxin
Non-invasive, produces tetanospasmin, toxin genes plasmid encoded, spreads via bloodstream and retrograde transport, binds to ganglioside receptors and blocks release of inhibitory interneurones convulsive contractor of voluntary muscles
Tetanus/lock jaw
Tonic muscle spasms, trismus (jaw), opisthotonus (spine bent), respiratory difficulties, cardiovascular instability (sympathetic nervous system), increased muscle tone
Most common entry site of Clostridium tetani
Via feet
Clostridium tetani treatment
Antitoxin (horse/human), Penicillin/metronidazole, drugs for spasms, muscle relaxants, respiratory support
Prevention of Clostridium tetani
Toxoid
Epidemiology of Clostridium tetani
1 millon required hospital treatment each year
