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Core Conditions - Other > Infectious Diseases > Flashcards

Infectious Diseases Flashcards

1
Q

What is the definition of meningitis?

How is this different to encephalitis?

A

meningitis is inflammation of the leptomeningeal coverings (pia mater & arachnoid) of the brain

it affects the extremes of age due to impaired immunity

encephalitis involves inflammation of the brain parenchyma

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2
Q

What are the typical causative agents of meningitis?

A

BACTERIA

  • Streptococcus pneumoniae
  • Neisseria meningitidis
  • Haemophilus influenzae type B
  • there are also some viral, fungal, parasitic and non-infectious causes
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3
Q

What are the typical causative agents of encephalitis?

A

there are infectious and non-infectious causes

it is typically caused by VIRUSES

the main cause is the herpesvirus

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4
Q

What are the typical symptoms associated with meningitis?

A
  • photophobia
  • neck stiffness
  • headache
  • fever
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5
Q

What are the typical symptoms of encephalitis?

A
  • altered state of consciousness
  • seizures
  • personality changes
  • cranial nerve palsies
  • speech problems
  • motor and sensory deficits
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6
Q

What investigations are performed for meningitis and encephalitis?

A

Meningitis:

  • lumbar puncture is performed to obtain CSF

Encephalitis:

  • blood cultures
  • neuroimaging via MRI scan
  • CSF analysis
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7
Q

What is involved in the initial management of meningitis?

A

empirical antimicrobial therapy should be started promptly until the causative agent is identified

this involves ceftriaxone / vancomycin

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8
Q

What organisms tend to cause meningitis in neonates?

Which one occurs straight after birth and which one is a delayed infection?

A
  • Group B streptococcus is associated with infection in previous pregnancy and/or extended labour

this infection occurs early on in the life of the infant

  • E. coli tends to cause late neonatal infection
  • Listeria monocytogenes can also cause meningitis in neonates
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9
Q

What organisms tend to cause meningitis in children & teenagers?

A
  • Haemophilus influenzae tends to cause meningitis in people who are unvaccinated
    • this tends to be someone from a poor country or who’s parents don’t believe in vaccines
  • Neisseria meningitides is a gram-negative diplococci that can also be responsible
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10
Q

What organism most commonly causes meningitis in adults and the elderly?

A

Streptococcus pneumoniae

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11
Q

When does Listeria monocytogenes typically cause meningitis?

A
  • the elderly
  • alcoholics
  • consuming cheese / unpasteurised milk
    • it likes cold environments and grows on refridgerator items
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12
Q

What are the 2 demonstratable signs associated with meningitis?

A
  • Brudzinski’s sign
  • Kernig’s sign
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13
Q

What is Brudzinski’s sign?

A
  • severe neck stiffness causes a patient’s hips and knees to flex when the neck is flexed
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14
Q

What is Kernig’s sign?

A
  • Severe stiffness in the hamstrings causes an inability to straighten the leg when the hip is flexed to 90 degrees
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15
Q

What are the signs of infection that are specific to meningitis?

A
  • fever
  • tachycardia
  • hypotension
  • skin rash - petechiae - think meningococcal septicaemia
    • ​if there is a skin rash, think Neisseria meningitidis
  • altered mental state
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16
Q

What 3 investigations are performed for suspected meningitis and why?

A

Bloods:

  • two sets of blood cultures

Imaging:

  • CT scan to exclude bleeding & raised intracranial pressure

Lumbar puncture:

  • to obtain CSF which is sent for MC&S and Gram staining
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17
Q

When should lumbar puncture be avoided as an investigation for meningitis?

A
  • if there are neurological signs suggesting raised ICP
  • if there is a superficial infection over LP site
  • coagulopathy
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18
Q

In normal CSF, what is the:

  • appearance
  • white cell count
  • protein
  • glucose
  • Gram stain
A
  • it has a clear appearance
  • it has very low white cell count
  • it has normal levels of protein and glucose
  • Gram stain is normal
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19
Q

How do the following characteristics of CSF change if there is bacterial infection?

  • appearance
  • white cell count
  • protein
  • glucose
  • Gram stain
A
  • appearance is turbid
  • white cell count is VERY HIGH with many NEUTROPHILS
  • protein is massively increased
  • glucose is massively decreased
    • ​this is because bacterial infections take up sugar for nutrition, whereas viral infections do not
  • Gram stain is positive
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20
Q

How are the following characteristics of CSF changed in viral infections?

  • appearance
  • white cell count
  • protein
  • glucose
A
  • the appearance is clear/cloudy
  • white cell count is high with lots of LYMPHOCYTES
  • protein is slightly raised
  • glucose is normal
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21
Q

How are the following characteristics of CSF changed in TB/fungal infection?

  • appearance
  • white cell count
  • protein
  • glucose
A
  • the appearance is clear/cloudy
  • the white cell count is high with lots of LYMPHOCYTES
  • protein is slightly raised
  • glucose is slightly decreased
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22
Q

What infection is suspected if someone has a non-blanching rash?

What is the treatment for this?

A
  • Neisseria meningitidis infection is suspected
  • if someone has a non-blanching rash OR meningococcal septicaemia, they need to be admitted
  • they are given a single dose of IV benzylpenicillin
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23
Q

What is the general treatment for bacterial meningitis?

A
  • IV ceftriaxone (3rd generation cephalosporin)
  • oral corticosteroids are considered as they reduce inflammation of the meninges
    • this is dexamethasone usually
  • OCS should NOT be given if meningococcal septicaemia is suspected
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24
Q

If you are thinking of treating bacterial meningitis but the patient’s consciousness is affected, what other treatment should be considered and why?

A
  • if consciousness is affected, consider IV aciclovir
  • this covers encephalitis, as the most common cause of encephalitis is viral (herpes virus)
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25
Q

What treatment should be given to close contacts of someone with bacterial meningitis?

A
  • prophylaxis should be given to close contacts
  • this involves rifampicin or ciprofloxacin
26
Q

What is the definition of infective endocarditis?

How common is it?

A
  • it is the infection of endocardial structures
    • this mainly involves heart valves
  • it involves life-threatening inflammation of the endocardium (innermost layer of the heart)
  • it is quite uncommon
27
Q

What are the 4 causative organisms of infective endocarditis?

A
  • Streptococci
  • Staphylococci
  • Enterococci
  • other organisms (HACEK organisms)
    • these will have a negative blood culture
28
Q

What are the risk factors for infective endocarditis?

A
  • having abnormal heart valves
    • e.g. congenital
    • post-rheumatic
    • calcification / degeneration
  • prosthetic heart valves
  • IV drug use
  • turbulent blood flow (e.g. PDA or VSA)
  • recent dental work
29
Q

What is the difference in the way in which streptococci and staphylococci affect the heart valves in infective endocarditis?

A
  • streptococci need a damaged heart valve in order to attack
    • there needs to be abnormal heart valves
  • staphylococci doesn’t need damaged valves to infect the heart, but it is harder for them to enter the body
30
Q

What valve would you expect to be affected if an IVDU gets infective endocarditis?

A
  • you would expect an infection of the first valve that is encountered from their venous system
  • this would be the tricuspid valve
  • infective endocarditis of the tricuspid valve - think IVDU
31
Q

What are the symptoms of infective endocarditis?

A
  • fever with sweats / chills / rigors
  • malaise
  • arthralgia (pain in a joint)
  • myalgia (pain in a muscle / group of muscles)
  • confusion
32
Q

What are the signs of infective endocarditis?

A
  • pyrexia
  • tachycardia
  • signs of anaemia
  • finger clubbing
  • new murmur
    • frequency mitral > aortic > tricuspid > pulmonary
  • splenomegaly
  • vasculitic lesions
33
Q

What are the 3 types of vasculitic lesion associated with infective endocarditis?

A
  • Osler’s nodes
    • these are tender, painful lesions on the fingers and toes
    • they are red-purple, slightly raised and often have a pale centre
  • Roth’s spots
    • red spots with white or pale centres that are found on the retina
  • Janeway lesions
    • these are non-tender, haemorrhagic lesions that occur on the thenar and hypothenar eminences
34
Q

What mnemonic is used to remember the features of infective endocarditis?

A

FROM JANE with <3

  • F - Fever
  • R - Roth spots
  • O - Osler nodes
  • M - Murmur
  • J - Janeway lesions
  • A - Anaemia
  • N - Nail-bed haemorrhage
  • E - Emboli
  • occasionally it can present with haematuria (which tends to be microscopic) due to emboli travelling to the kidneys
35
Q

What are the 6 buzzwords to remember when thinking about infective endocarditis?

A
  • prosthetic valves
  • previous / recent dental procedure
  • new onset murmur
  • vegetation present on Echo
  • right heart (this is usually due to IVDU)
  • indwelling catheter (another point of introducing infection)
36
Q

What investigations are conducted for suspected infective endocarditis?

A

Bloods:

  • FBC - showing high neutrophils & normocytic anaemia
  • ESR / CRP
  • U&Es
  • Rheumatoid factor positive

Duke Criteria:

  • in order to determine this 3 blood cultures are needed, each 1 hour apart within 24 hours for diagnosis

Urgent Echo

37
Q

What is needed for the diagnosis of infective endocarditis?

What treatment is given in the meantime?

A
  • 3 blood cultures are needed, each at least 1 hour apart and all need to be taken within 24 hours
  • broad spectrum antibiotics are given until sensitivity is reported
38
Q

What are the possible complications of infective endocarditis?

A
  • congestive heart failure
  • valve incompetence
  • aneurysm formation
  • systemic embolisation
  • renal failure
  • glomerulonephritis
39
Q

What is the management for infective endocarditis affecting native valves?

A

antibiotics are given for 4 - 6 weeks

  • for penicillin-sensitive Streptococcus viridans the treatment is benzylpenicillin + gentamicin
  • for Staphylococcus aureus, the treatment is flucloxacillin
  • if resistant or penicillin-allergic, then vancomycin is given instead
40
Q

What is the treatment for infective endocarditis in someone with prosthetic valves?

A
  • this is usually caused by Staphylococci
  • the treatment is flucloxacillin + rifampicin + gentamicin
  • if the patient is allergic to penicillin then vancomycin is given instead of flucloxacillin
41
Q

What is the definition of gastroenteritis?

A

acute inflammation of the lining of the GI tract,

manifested by nausea, vomiting, diarrhoea and abdominal discomfort

42
Q

What are the viral causes of gastroenteritis?

A
  • rotavirus
    • ​this was the most common cause in children
    • they are now vaccinated against it, so it is not as common
  • adenovirus
  • astrovirus
  • calcivirus
43
Q

What are the bacterial causes of gastroenteritis?

A
  • Campylobacter jejuni
  • Escherichia coli (particularly 0157)
  • Salmonella
  • Shigella
  • Vibrio cholerae
  • Listeria
  • Yersinia enterocolitica
44
Q

What are the protozoal causes of gastroenteritis?

A
  • Entamoeba histolytica
  • Cryptosporidium parvum
  • Giardia lamblia
45
Q

What is dysentry and how is it different from diarrhoea?

A
  • it involves intestinal inflammation that primarily involves the colon
  • it involves mild to severe stomach cramps and severe diarrhoea
  • the diarrhoea associated with dysentry contains blood
46
Q

What mnemonic can be used to remember the organisms which cause dysentry?

A

CHESS

  • C - Campylobacter / Clostridium difficile
  • H - Haemorrhagic E. coli
  • E - Entamoeba histolytica
  • S - Shigella
  • S - Salmonella
47
Q

What are the causes of gastroenteritis that present with diarrhoea and not dysentry?

A
  • Campylobacter / Clostridium difficile
  • Staphylococcus aureus
  • Vibrio cholera
  • E. coli
  • Bacillus cereus
  • Salmonella
48
Q

What clues might be in the history of someone presenting with diarrhoea due to C. diff or Staph aureus infection?

A
  • C. diff is associated with the use of antibiotics and/or antiperistaltic drugs
  • Staph aureus is associated with food

it comes on 1 - 6 hours after eating and is short-lived

49
Q

What clues might be in the history of someone presenting with diarrhoea due to Vibrio cholera and E. coli?

A
  • Vibrio cholera is associated with rice water diarrhoea, poor sanitation and shock
  • E. Coli is associated with consumption of leafy vegetables
50
Q

What clues might be in the history of someone presenting with diarrhoea due to salmonella or Bacillus cereus?

A

Salmonella:

  • mainly comes from eggs and can also come from poultry
  • may present with constipation
  • multiplies in Peyer’s patches of the intestine

Bacillus cereus:

  • associated with reheated rice
  • can cause cerebral abscess
51
Q

What clues might be in the history of someone presenting with diarrhoea due to haemorrhagic E. coli?

What does this infection cause?

A
  • it is associated with consumption of leafy vegetables
  • it is characterised by bloody diarrhoea followed by haemolytic uraemic syndrome
52
Q

What clues might be in the history of someone presenting with diarrhoea due to Entamoeba histolytica or campylobacter?

A
  • Entamoeba histolytica is associated with poor sanitation, tropical places and MSM
  • Campylobacter is associated with uncooked poultry
53
Q

What clues might be in the history of someone presenting with diarrhoea due to shigella?

A
  • person-to-person contact
  • poor sanitation
  • MSM
54
Q

What are the symptoms of gastroenteritis?

A
  • sudden onset nausea
  • vomiting
  • anorexia
  • diarrhoea (+/- blood)
  • abdominal pain
  • fever and malaise
55
Q

What signs might be present on examination of someone with gastroenteritis?

A
  • check mucous membranes for signs of dehydration
    • assess skin turgor and capillary refill
  • measure HR and BP to assess whether patient is in shock
  • temperature
56
Q

What other investigations are carried out for gastroenteritis?

A

Bloods:

  • FBC
  • ESR / CRP
  • U&Es will be deranged - low potassium in severe D&V

Stool MC&S:

  • bacterial pathogens
  • ova cysts (eggs)
  • parasites
57
Q

What is the treatment for gastroenteritis when the patient has no systemic signs?

A
  • systemic signs include shock and dehydration
  • supportive therapy is given
  • bed rest and fluid and electrolyte replacement with oral rehydration solution
    • this is given due to loss of nutrients / vitamins through diarrhoea/vomiting
58
Q

What is the treatment for gastroenteritis when there are signs of systemic illness?

How is systemic illness defined and what investigation is carried out?

A
  • systemic illness is defined as:
    • temperature > 39oC or dehydration
    • visible blood
    • or duration > 2 weeks
  • patient is admitted and given oral fluids
    • ​IV rehydration is required for severe vomiting
  • antibiotics are given if the infective organism is identified
  • a direct faecal smear then culture is obtained
59
Q
A

Hepatitis A

  • jaundice, RUQ pain and raised ALT & AST are suggestive of hepatitis
  • Jamaica is an endemic country and hepatitis A is faeco-orally transmitted
60
Q

What signs and tests would point towards a diagnosis of hepatocellular carcinoma?

A
  • combination of jaundice, hepatomegaly and weight loss
  • when combined with a raised aFP
61
Q
A

B - positive nitrites and Gram-negative bacilli

  • this is an E. coli infection
  • nitrites are specific for E. coli
  • this is more common in women after sexual intercourse as their urethra is shorter
62
Q
A

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