CNS Infections - Bacterial and Fungal Meningitis (27) Flashcards Preview

Clinical Pathology > CNS Infections - Bacterial and Fungal Meningitis (27) > Flashcards

Flashcards in CNS Infections - Bacterial and Fungal Meningitis (27) Deck (60):
1

CNS infections

Meningitis (bacterial, viral, TB, cryptococcus), brain abscess, encephalitis, toxin mediated

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What is meningitis?

Infection of CSF/meninges

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How does meningitis present?

Acute fever, headache, neck stiffness, +/- rash, fully conscious, usually viral

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What is encephalitis?

Infection of brain tissue

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How does encephalitis present?

Acute fever, headache, neck stiffness, altered conscious level, seizures, focal neurological signs, usually viral

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What is a brain abscess?

Abscess within brain tissue

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How does brain abscess present?

Insidious onset of fever, headache, +/- neck stiffness, +/- altered conscious level, seizures, focal neurological signs, usually bacterial (parasitic?)

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How does invasion via micro-organisms occur?

Blood-borne invasion (blood-brain barrier/blood CSF barrier), peripheral nerves

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What does normal CSF look like?

Clear

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Polymorphic nucleoles likely to be

Bacterial

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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)

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Natural habit of N. meningitidis

Nasopharynx, 5-20% carriers (increased smokers), half strains non-capsulate, increase in Gp A carriage rates before epidemics

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Factors affecting intravascular survival (N. meningitidis)

Capsule - protects against complement-mediated bacteriolysis and phagocytosis

Acquisition of iron from transferrin

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N. meningitidis BBB

Cross BBB and multiply in subarachnoid space, can remain in blood stream/not cross BBB

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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

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Is rash blanching or non-blanching?

Can be blanching early in disease and progress to be non-blanching

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Treatment of N. meningitidis

Ceftriaxone, cefotaxime (Penicillin)

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Chemoprophylaxis of contacts on invasive disease (N. meningitidis)

Close/kissing contacts, Rifampicin/Ciprofloxacin

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Vaccination for N. meningitidis

Active against Group A and C and W135 (not against Group B)

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When is peak of N. meningitidis?

Winter

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Local outbreaks of N. meningitidis

Population of susceptible individuals, high transmission rate, virulent, capsulate strain

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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)

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Normal carriage of H.influenzae

Restricted to humans, 25-80% carry non-capsulate strains, 5-10% carry capsulate strains

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Throat carriage of H.influenzae

Invasion of submucosa > blood stream > (invasive infections if meningitis, infants, >2 months - 2 years)

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Virulence factors of H.influenzae

Type b capsule, Fimbriae, IgA proteases, outer membrane proteins/lipolysaccharide (intercurrent viral infection)

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Treatment of H.influenzae

Ceftriaxone, cefotaxime (ampicillin, B-lactamase producing strains common)

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Chemoprophylaxis of H.influenzae

Rifampicin

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Vaccines for H.influenzae

Type b conjugates vaccines (dramatic reduction in incidence of invasive disease)

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Streptococcus pneumoniae

Gram positive cocci, cells in pairs, requires blood/serum for growth, a-haemolytic activity on blood agar (green)

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What test can be done to see if Step pneumoniae is present?

Optochin test (ethyldydrohupreine)

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Who does Step pneumoniae effect?

All ages, more severe in elderly and immunocompromised

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Treatment of Step pneumoniae

Ceftriaxone, cefotraxime (Penicillin resistance)

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Vaccine for Step pneumoniae

Conjugate vaccine available against serotypes

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Steroids for meningitis in adults

Must be given shortly before/with first dose of antibiotics, should be given if Step pneumoniae suspected

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Neonatal meningitis usually caused by

Group B beta-haemolytic streptococci, E.coli, Listeria monocytogenes (rare)

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Neonatal extent of infection (variable onset)

Early 5 days - meningitis

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Treatment of neonatal meningitis

Cefotaxime (ampicillin and gentamicin)

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Acute complications of meningitis

Death, overwhelming sepsis, raised ICP

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Chronic complications of meningitis

Deafness, delayed development, seizures, stroke, hydrocephalus

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Lymphocytic meningitis

Viral (Enterovirus/HSV 2/polio), benign outcome

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Consequence of polio meningitis

Paralysis

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Bacteria causing lymphocytic meningitis

Spirochete - treponemal/borrelia

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Lymphocytic meningitis - TB

Insidious onset

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Risk factor for TB

Immunocompromised, alcoholic, endemic area

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Detection of TB

Ziehl Neelsen/Fluorescent antibody stain

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Toxoplasma gondii encephalitis

Protozoan, contracted by eating contaminated meat, resembles glandular fever, immunocompromised

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Cryptococcal meningitis

Lymphocytic meningitis, yeast, common with late HIV, insidious onset

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Where are yeast forms of Cryptococcal meningitis seen?

In CSF in Indian Ink stain

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Cryptococcal meningitis treatment

Prolonged course - amphotericin, flucytosine, fluconazole

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Encephalitis

Altered conscious level, HSV 1 most common, affects temporal lobes, 50% over 50s

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Diagnosis of encephalitis

Detecting viral nuclei acid in CSF (PCR)

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Rabies encephalitis

Common, dog, fox, bat bites, 100% mortality, preventable by vaccination

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Clostridium tetani

Gram positive spore forming bacillus, terminal round spore (drumstick), strict anaerobe

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How is Clostridium tetani spread?

Contaminated soil > wound (major/minor)

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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

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Tetanus/lock jaw

Tonic muscle spasms, trismus (jaw), opisthotonus (spine bent), respiratory difficulties, cardiovascular instability (sympathetic nervous system), increased muscle tone

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Most common entry site of Clostridium tetani

Via feet

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Clostridium tetani treatment

Antitoxin (horse/human), Penicillin/metronidazole, drugs for spasms, muscle relaxants, respiratory support

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Prevention of Clostridium tetani

Toxoid

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Epidemiology of Clostridium tetani

1 millon required hospital treatment each year

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