Infection Flashcards
Infective causes of meningitis
Bacterial
Viral
Fungal
Parasitic
Non-infective causes of meningitis
Paraneoplastic
Drug side effects
Autoimmune e.g. vasculitis/SLE
How does infection enter body
Via bloodstream i.e. bacteraemic
Neurosurgical complications (Post op, Infected shunts, Trauma)
Extracranial infection e.g. nesopharynx, ear, sinuses (nasal carriage, otitis media, sinusitis etc)
Pathophysiology of infection
Bacteria enter CSF and can be isolated from immune cells due to BBB, replication
Blood vessels become leaky
Therefore WBCs can enter the CSF, meninges and brain
Meningeal inflammation with or without brain swelling
Key symptoms of patient with infection
Fever
Headache
Neck stiffness (Meningism)
What % of people infected with bacterial meningitis die and what % have permanent effects as result of infection
5% mortality (when treated)
20% permanent effects
Permanent effect of bacterial meningitis
Skin scars Amputation Hearing loss Seizures Brain damage
**Immediate management of bacterial meningitis
- Assess GCS (Glasgow Coma Scale)
- Blood cultures
- Broad spectrum antibiotics
- Steroids (IV dexamethasone)
Medial management of bacterial meningitis
First line antibiotics – either ceftriaxone or cefotaxime
Steroids to reduce neurological sequelae and therefore reduce morbidity (particularly with strep. Pneumoniae)
Examples of first line (broad spectrum) antibiotics for bacterial meningitis
Cephalosporins such as:
Ceftriaxone
OR
Cefotaxime
What can GCS help us determine
How sick the patient is, the lower the GCS, the sicker the patient!
If they can maintain their own airway (if <8 then no -> intubate!)
If there is any raised intracranial pressure
3 examples of what GCS tests
Best eye response
Best verbal response
Best motor response
What type of antibiotic is cephalosporins
Beta-lactam family
need a bactericidal antibiotic to eliminate infection quickly
What special considerations need to be taken for those to use antibiotics
Are they penicillin allergic?
Immunocomprimised?
Recent travel (<6 months)?
If someone has a reaction with penicillin, what is the chance of a reaction with cephalosporin
10%
If penicillin allergic patient develops a rash reaction, what is give
Cephalosporin
If penicillin allergic patient has an anaphylactic reaction, what is given
Chloramphenicol
If patient with bacterial meningitis is immunocomprimised, what can they be at risk of?
Listeria
If bacterial meningitis patient is immunocompromised, what is added to cephalosporin and why
Amoxicillin
Risk fo listeria
Why is it important to ask about any recent travel in bacterial meningitis
Some countries have higher incidence of penicillin resistant strep pneumoniae
What is added to cephalosporin if patient suspected to have penicillin resistant infection from recent travel?
Vancomycin
*Once immediate management of bacterial meningitis is done, what is done after to DIAGNOSE MENINGITIS
Lumbar puncture
What is done with the lumbar puncture sample
Microscopy, Gram stain, Culture, Protein, Glucose, viral PCR
Viral or bacterial?
Complications of lumbar puncture
Abnormal clotting (platelets/coagulation) Petechial rash Raised intracranial pressure
Causative organisms of meningitis
Neisseria meningitidis
Streptococcus pneumoniae
How would you tell causative organism of meningitis between Neisseria and strep pneumoniae
Gram stain:
gram Negative cocci = Neisseria
gram Positive cocci = Pneumococcus (strep.pneumoniae)
What % of adults and teenagers carry Neisseria meningitidis
5-11% adult carriage
25% teenagers
Causes of acute bacterial infection
Neisseria meningitidis (gram negative diplococci)
Strep. pneumoniae (gram positive diplococci)
Listeria spp. (gram positive rod)
Group B Strep (gram positive cocci)
Haemophilus influenzae B (gram negative rod)
E.coli (gram negative rod)
Causes of acute viral infection
Enterovirus
Herpes Simplex Virus (HSV)
Varicella Zoster Virus (VZV)
Causes of chronic bacterial infection
Mycobacterium tuberculosis (TB) Syphilis
Causes of chronic fungal infection
Cryptococcal
Bacterial infection causes in neonates
Listeria monocytogenes
Group B streptococcus
Escherichia coli
Bacterial infection causes in children
Neisseria meningitidis
Streptococcus pneumoniae
Haemophilus influenzae
Bacterial infection causes in adults
Neisseria meningitidis
Streptococcus pneumoniae
Bacterial infection causes in elderly
Neisseria meningitidis
Streptococcus pneumoniae
Listeria
Once condition of patient with Neisseria meningitidis (or meningitis in general) is more stable, what would you do after
Inform Public Health England
For Neisseria, identify ‘close contacts’ who have a 1/300 risk of developing meningitis (particularly first 7 days)
Antibiotic prophylaxis reduces risk and prevents onward transmission
Examples of antibiotic prophylaxis to reduce risk and prevent onward transmission
Ciprofloxacin
Rifampicin
What is Encephalitis
Causes of Encephalitis
Infection (and inflammation) of the brain parenchyma
Usually viral:
*Herpes Simplex
Varicella Zoster
Other causes of encephalitis (not herpes simplex or varicella zoster)
ASK ABOUT TRAVEL Japanese encephalitis virus Tick-borne encephalitis Rabies West Nile etc
Non-infective - autoimmune, paraneoplastic
Clinical presentation of encephalitis
Hours to days: preceding “flu-like” illness
Then:
Altered GCS - confusion, drowsiness, coma
Fever, Seizures, Memory loss
Also: headache, altered behaviour and altered mental status.
Less commonly; hemiparesis, dysphagia, seizure and coma.
Investigations of encephalitis
Viral serology (LP and CSF studies) CT: Check for space occupying lesions
MRI head with or without EEG Lumbar puncture after Lymphocytic CSF Viral PCR HIV test
Treatment of encephalitis
Mostly supportive
Aciclovir if HSV or VZV
(2-3 weeks of antivirals providing end of treatment CSF is –ve on PCR; extend course if ongoing viral presence)
Infection process of tetanus
Inoculation through skin with Clostridium tetani spores (found globally in soil)
e.g. stepping on a nail, dirty wounds
Bacteria produce toxins
What toxins are produced in tetanus infection
Tetanolysin (tissue destruction)
Tetanospasmin (clinical tetanus)
What bacteria causes tetanus and what type of bacteria is it
Clostridium tetani
Gram +ve anaerobe with spores
Pathophysiology of tetanus
Tetanospasmin toxin in tetanus can travel retrogradely along axons
Interferes with neurotransmitter release -> increased neurone firing -> unopposed muscle contraction and spasm
Incubation time for tetanus
8 days
Generalised tetanus signs and symptoms
Opisthotonos (generalised spasms) Lock jaw and possibly risus sardonicus Also: Respiratory compromise Pain Hypertension, tachycardia, arrhythmias Fever
Localised tetanus signs and symptoms
Injury to right head
2 days later unopposed flexion of fingers and spasm of forearm
Management of tetanus
Vaccination to prevent
Supportive - muscle relaxants and paracetamol/cooling
Immunoglobulin to mop up toxin
Metronidazole to clear any residual bacteria
How many people die of rabies per year
35-50,000
Once symptomatic, invariably fatal
Transmission of rabies
Inoculation through skin with saliva of rabid animal (dogs, cats, foxes etc) e.g. lick, lite, splash
Travels retrogradely along nerves
Incubation time of rabies
2 weeks to years depending on site and size on inoculation
Pathophysiology of rabies
Travels retrogradely along nerves
Reaches CNS
Furious or paralytic presentation
Management of rabies
Sedatives
Prophylaxis:
Pre-exposure prophylaxis (vaccination)
Post-exposure prophylaxis (vaccination and immunoglobulin)
What is meningitis
Inflammation of the meninges
What is Shingles
Varicella zoster virus reactivation
Herpes zoster
Aetiology of Shingles
Varicella-zoster. Usually occurs in childhood, but lies dormant for years/decades.
Pathophysiology of Shingles
After infection, the virus lies dormant in the sensory nervous system in the geniculate, trigeminal or dorsal root ganglia.
Eventually flares up -> Virus travels down the affected nerve over 3-4 days, causing perineural and intraneural inflammation.
Clinical presentation of Shingles: pre-eruptive
Pre-eruptive: No skin lesions, but burning itching in one dermatome. Usually a day or two before eruption.
Rash does not cross dermatomes.
Clinical presentation of Shingles: eruptive
Eruptive phase: Skin lesions appear (infectious until dried). Erythmatous, swollen plaques.
Rash does not cross dermatomes
Diagnosis of Shingles
Clinical
Based on rash within a dermatome
Treatment of Shingles
Oral aciclovir
Protein levels in infection that is: Bacterial Viral TB Cryptococcal
Bacterial - low
Viral - normal
TB - low
Cryptococcal - low
Cells found in microscopy in infection that is: Bacterial Viral TB Cryptococcal
Bacterial - neutrophil polymorphs
Viral - lymphocytes
TB - lymphocytes
Cryptococcal - lymphocytes
Appearance of CSF in infection that is: Bacterial Viral TB Cryptococcal
Bacterial - cloudy
Viral - clear
TB - ‘fibrin web’
Cryptococcal - ‘fibrin web’
Viral causes of meningitis
Mumps virus Echo virus Coxsackie virus Other enteroviruses Herpes simplex virus Lymphocytic chorio meningitis virus Poliovirus
Diagnosis of meningitis
Lumbar puncture - CSF Blood culture Nose and throat swabs - put on chocolate agar and examined for virus Stool Blood is taken for serology (antibodies)
What tests are done with CSF in diagnosis of meningitis
Cell count, gram film, protein assay, glucose assay, culture on blood agar/chocolate
Appearance of CSF
Gin-clear normally
Clinical presentation of meningitis
Stiffness of neck
Photophobia
Severe headache
Bacterial or viral meningitis: Fever, unwell and may have a rash (characteristically haemorrhagic)
What is meningitis
Inflammation of the pia and arachnoid mater
Micro-organisms infect the cerebrospinal fluid
What is encephalitis
Inflammation of the cerebral cortex
Clinical symptoms of encephalitis
Lethargy and fatigue
Decreased levels of consciousness and fever
Cause of encephalitis
Generally viral infection and viral causes are: Herpes simplex virus Varicella zoster virus Paroviruses HIV Mumps virus Measles virus
Diagnosis of encephalitis
CSF - cultured on cell monolayers to detect viral growth. HSV can be detected by polymerase chain reaction
Serology of blood - acute and convalescent blood is taken to detect a rise in antibody to HSV, VZV, mycoplasma, mumps virus and measles
