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Infectious diseases Flashcards

1
Q

What is infective endocarditis

A

Infection of endocardium or vascular endothelium of heart

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2
Q

Risk factors for infective endocarditis

A
  • IV drug use
  • IV cannula
  • Poor dental hygiene
  • Dental treatment
  • Skin and soft tissue infection
  • Cardiac surgery
  • Pacemaker
  • Prosthetic valves (aortic and mitral)
  • Congenital heart disease
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3
Q

Causes of infective endocarditis

A
  • Staph. Aureus  IVDU, diabetes and surgery
  • Staph. Viridans  dental problems
  • Strep. Mutans  poor oral dentition
  • Pseudomonas aeruginosa
  • Candida albicans  immunocompromise
  • Staph. Epidermis  prosthetic valve
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4
Q

Presentation of infective endocarditis

A
  • Headache
  • Fever
  • Malaise
  • Confusion
  • Night sweats
  • Joint pain and abscesses
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5
Q

Examination findings in infective endocarditis

A
  • Finger clubbing
  • Roth spots = retinal haemorrhages with white or clear centres
  • Osler nodes = tender nodules in digits
  • Murmur
  • Janeway lesions = haemorrhages and nodules in fingers
  • Anaemia
  • Nail haemorrhages (splinter)
  • Emboli
  • Embolic skin lesions = black spots on skin
  • Petechiae = small red/purple spots caused by bleeds in skin
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6
Q

Investigations of infective endocarditis

A
  • Use Dukes criteria
  • Blood cultures = 3 sets from different sites over 24 hrs before antibiotics started
  • Bloods  CRP and ESR raised, Normochromic and normocytic anaemia, Neutrophilia
  • Urinalysis = Look for haematuria
  • CXR = Cardiomegaly
  • ECG = Long PR interval at regular intervals
  • Transoesophageal echo  Visualising mitral lesions and possible development of aortic root abscess
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7
Q

Duke’s criteria for infective endocarditis

A

Major criteria:
- Persistently +ve blood culture for typical organisms
- ECHO shows vegetation, dehiscence, abscess
- New valvular regurgitation murmur
- Coxiella burnetii infection

Minor criteria:
- Predisposing heart condition or IVDU
- Fever >38
- Emboli to organs/brain, haemorrhages
- GLomerulonephritis, Osler’s nodes, Roth spots, rheumatoid factor
- Positive blood cultures that do no meet specific criteria

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8
Q

Diagnosis using Duke’s criteria

A

2 major
1 major and 3 minor
5 minor
Histological findings
+ve gram stain or cultures from surgery or autopsy

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9
Q

Management of infective endocarditis

A
  • Consult microbiologist
  • Antibiotic treatment for 4-6 weeks
    o Staphylococcus = vancomycin and rifampicin
    o Not staph = penicillin (Benzylpenicillin and gentamycin)
  • Treat complications = stroke rehab, abscess drainage
  • Surgery = Removing valve and replacing with prosthetic one
    o Operate if infection cannot be cured with antibiotics
    o Operate to remove infected devices
    o Operate to remove large vegetations before they embolise
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10
Q

Prevention of infective endocarditis

A

Good oral health

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11
Q

Complications of infective endocarditis

A
  • Stroke
  • Pulmonary embolus
  • Bone infections
  • Kidney dysfunction
  • MI
  • Arrhythmia
  • Heart failure
  • Heart block
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12
Q

Risk factors for tuberculosis

A
  • Origination from high-prevalence country
  • Immunosuppression (HIV/medications)
  • Homeless, alcoholics, IVDU, prisoners
  • Children
  • Malnutrition
  • Smoking
  • Close contact to someone with active TB
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13
Q

Causes of tuberculosis

A
  • Mycobacterium tuberculosis (aerobic acid-fast bacilli)
  • Mycobacterium bovis
  • Mycobacterium africanum
  • Mycobacterium microti
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14
Q

Presentation of TB

A
  • Fever and night sweats
  • Anorexia and weight loss
  • Productive cough (>3weeks) with occasional haemoptysis
  • Malaise
  • Breathlessness
  • Pleuritic pain
  • Hoarse voice = laryngeal involvement
  • Clubbing
  • Erythema nodosum
  • Consolidation (pleural effusion)
  • Lymphadenopathy
  • Bone/joint pains, back pain and joint swelling
  • Abdo/pelvic pain, constipation, bowel obstruction
  • Sterile pyuria
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15
Q

CXR in TB

A

Cavitation
Pleural effusion
Mediastinal/hilar lymphadenopathy
Parenchymal infiltrates in upper lobes

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16
Q

Other investigations in TB

A

Sputum culture (x3)  Ziehl-Neelsen stain for acid and alcohol-fast bacilli = turns bright red against blue background

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17
Q

Screening tests for TB

A
  • Mantoux test = previous vaccination, latent or active TB
    o If positive then indicated immunity and thus contact with TB
  • Interferon gamma release assays
    o Used when no features of active TB but positive Mantoux test to confirm latent TB
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18
Q

Causes of false negative mantoux test

A

immunosuppression
sarcoidosis
lymphoma
extremes of age
fever
hypoalbuminaemia
anaemia

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19
Q

Risk factors for developing active TB from latent TB

A

silicosis
chronic renal failure
HIV positive
solid organ transplantation with immunosuppression
IVDU
haematological malignancy
anti-TNF Tx
previous gastrectomy

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20
Q

Management of active TB

A
  • Notify PHE and contact tracing
  • Rifampicin (6 months)
  • Isoniazid (6 months)
  • Pyrazinamide (2 months)
  • Ethambutol (2 months)
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21
Q

Side effects of rifampicin

A

red urine, hepatitis, drug interactions

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22
Q

Side effects of isoniazid

A

hepatitis and peripheral neuropathy
o Prescribe pyridoxine (vit B6) as well

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23
Q

Side effects of pyrazinamide

A

hepatitis, hyperuricaemia (gout), rash

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24
Q

Side effects of ethambutol

A

colour blindness and reduced visual acuity

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25
Q

Treatment of latent TB

A

o 3m isoniazid (with pyridoxine) and rifampicin  <35y if hepatotoxicity concern
o 6m isoniazid (with pyridoxine)  HIV or transplant

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26
Q

Prevention of TB

A
  • Active case finding to reduce infectivity
  • Test for other infectious diseases = HIV, Hep B/C
  • Vaccination = Neonatal BCG
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27
Q

Epidemiology of infective diarrhoea

A
  • Highest prevalence in South Asia and Africa
  • Tends to be children and elderly
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28
Q

Risk factors for infective diarrhoea

A
  • Foreign travel
  • PPI and H2 antagonist use
  • Crowded area
  • Poor hygiene
  • Immunocompromised
  • Reduced gastric acid secretion
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29
Q

Causes of infective diarrhoea

A
  • Viral = Rotavirus (children), norovirus (adults), adenovirus, astrovirus
  • Bacterial = campylobacter jejuni, E.coli, salmonella, shigella spp, C. diff
  • Parasitic = Giardia lamblia, Entamoeba histolytica, Cryptosporidium
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30
Q

Presentation of infective diarrhoea

A
  • Watery diarrhoea
  • Blood usually indicates bacterial infection (Salmonella, E.coli and shigella)
  • Vomiting
  • Abdominal pain
  • Viral = Fever, fatigue, headache, muscle pain
  • Life-threatening  Toxic megacolon and perforation
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31
Q

Investigations for infective diarrhoea

A
  • Low MCV and/or Fe deficiency = coeliac disease or colon cancer
  • High MCV if alcohol abuse or decreased B12 absorption = coeliac disease or Crohn’s
  • Raised WCC if parasites
  • Raised ESR and CRP indicate infection, Crohn’s, UC or cancer
  • Stool culture if suspect bacteria, parasites or C.diff toxin
  • Sigmoidoscopy with biopsy
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32
Q

Management of infective diarrhoea

A
  • Oral rehydration and avoid high-sugar drinks in children
  • Antibiotics (C.diff)
    o Oral vancomycin for 10 days
    o Oral fidaxomicin (if recurrent infection within 12 wks)
    o Oral vancomycin + IV metronidazole (Life-threatening)
  • Anti-motility agents = loperamide hydrochloride
  • Anti-emetics = metoclopramide
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33
Q

Cause of enteric fever (typhoid)

A

Salmonella (transmitted via faecal-oral route)

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34
Q

Presentation of enteric fever

A
  • Headache
  • Fever
  • Arthralgia
  • Relative bradycardia
  • Abdominal pain, distension
  • Constipation ± diarrhoea
  • Rose spots
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35
Q

Management of enteric fever

A

Ciprofloxacin

36
Q

Complications of enteric fever

A
  • Osteomyelitis (esp in sickle cell)
  • GI bleed/perforation
  • Meningitis
  • Cholecystitis
  • Chronic carriage
37
Q

Risk factors for cholera

A
  • Foreign travel to Africa, Asia, Middle East and South America
  • Shellfish
38
Q

Cause of cholera

A

Vibro cholerae (gram neg)

39
Q

Presentation of cholera

A
  • Profuse ‘rice water’ diarrhoea
  • Dehydration
  • Hypoglycaemia
  • Hypokalaemia
  • Metabolic acidosis
40
Q

Management of cholera

A
  • Oral rehydration therapy
  • Antibiotics: doxycycline, ciprofloxacin
41
Q

Risk factors for legionella

A
  • Air conditioning systems
  • Foreign holidays
42
Q

Presentation of legionella

A
  • Flu-like symptoms (fever)
  • Dry cough
  • Relative bradycardia
  • Confusion
  • Lymphopaenia
  • Hyponatraemia
  • Deranged LFTs
43
Q

Investigations for legionella

A
  • Urinary antigen
  • CXR  mid-to-lower zone predominance of patchy consolidation, pleural effusions
44
Q

Management of legionella

A

Erythromycin/clarithromycin

45
Q

Cause of malaria

A
  • Plasmodium falciparum (severe)
  • Plasmodium vivax (benign)
  • Plasmodium ovale
  • Plasmodium malariae
46
Q

Risk factors for malaria

A
  • Foreign travel
47
Q

Protective factors for malaria

A
  • G6PD deficiency
  • HLA-B53
  • Absence of Duffy antigens
  • Sickle cell trait
48
Q

Presentation of malaria

A
  • Fever on alternating days
  • Headache
  • Myalgia
  • Hepatomegaly
49
Q

Cause of Hepatitis A

A

Infective hepatitis caused by RNA picornavirus via ingestion of contaminated food or water

50
Q

Risk factors for hepatitis A

A
  • Shellfish
  • Travellers
  • Food handlers
  • Household contact
  • Sexual contact
  • Overcrowding and poor sanitation facilitate spread
  • Injecting drug use
51
Q

Pathophysiology of hepatitis A

A
  • Spread via faecal-oral route
  • Short incubation period = 2-6 weeks
  • Causes acute hepatitis only (3-6 wks)
  • 100% immunity after infection
52
Q

Presentation of Hep A

A
  • Flu-like prodrome
  • Abdominal pain (RUQ)
  • Nausea and vomiting
  • Anorexia
  • Fever
  • Malaise
  • Jaundice
  • Tender Hepatosplenomegaly
53
Q

Investigations for Hep A

A
  • Bloods = low WCC, raised ESR
  • LFTs = raised serum bilirubin, bilirubinuria and raised serum AST/ALT
  • Viral markers = Hep A virus antibodies, Anti-HAV IgM
54
Q

Management of Hep A

A
  • Supportive treatment = resolves in 1-3 months
  • Basic analgesia
  • Avoid alcohol
55
Q

Prevention of Hep A

A
  • Vaccination + booster 6-12m later
    o People travelling to or going to reside in areas of high prevalence
    o Chronic liver disease
    o Haemophilia
    o MSM
    o IVDU
    o Occupational risk: lab workers, sewage workers, work with primates
  • Good hand hygiene
56
Q

Risk factors for Hep B

A
  • Healthcare personnel
  • Emergency and rescue teams
  • CKD/dialysis patients
  • Travellers
  • Homosexual men
  • IV drug users
57
Q

Transmission of Hep B

A
  • Blood borne transmission
    o Needle stick/sharing needles (IVDU, tattoos)
    o Sexual intercourse
    o Blood products
    o Vertical transmission = mother to child in utero/soon after birth
  • Horizontal transmission
    o Particularly in children
    o Minor abrasions or close contact with others
    o HBV can survive on household articles (toys, toothbrushes) for prolonged periods of time
58
Q

Pathophysiology of hep B

A
  • HBV (DNA) found in semen and saliva
  • Following infection, 1-10% of patients not clear virus  chronic Hep B  cirrhosis and decompensated cirrhosis and liver failure
  • Both cirrhosis and chronic infection can lead to hepatocellular carcinoma
  • Chronic Hep B will result in continuing hepatocellular damage
59
Q

Presentation of Hep B

A
  • Nausea
  • Fever
  • Malaise
  • Anorexia
  • Arthralgia
  • Rashes = urticaria and polyarthritis affecting small joints
  • After 1-2 weeks  jaundice
  • Hepatosplenomegaly
60
Q

Investigations for Hep B

A
  • HBsAg present 1-6 months after exposure
  • HBsAg presence for more than 6 months = carrier status/ chronic infection
  • Anti-HBs = immunity (exposure or immunisation), negative in chronic infection
  • Anti-HBc = previous or current infection
  • IgM anti-HBc = acute or recent infection, present for 6m
  • HbeAg = marker of infectivity
61
Q

Management of acute Hep B

A

o Supportive + monitor LFTs
o Avoid alcohol
o Manage close contacts by giving human normal immunoglobulin for Hep B and vaccination
o Monitor HBsAg at 6 months to ensure there is full clearance and no progression
o Majority will get spontaneous resolution and will not progress to chronic infection

62
Q

Management of chronic Hep B

A

o SC pegylated interferon-alpha 2A weekly = immunomodulatory
o Oral Nucleos(t)ide analogues daily (tenofovir)= inhibit viral replication

63
Q

Prevention of Hep B

A
  • Antenatal screening of pregnant mothers
  • Screening and immunisation of sexual and household contacts
  • Universal childhood immunisation
  • Universal screening of blood products
  • Sterile equipment and universal precautions in healthcare
  • Immunisation of healthcare workers and other risk groups
64
Q

Complications of Hep B

A
  • Cirrhosis
  • Liver failure
  • Hepatocellular carcinoma
65
Q

Hep D

A

RNA virus that can only survive in patient with hep B transmitted by blood-borne

66
Q

Risk factors for Hep C

A
  • People with haemophilia treated before screening of blood products was introduced
  • IV drug users
  • Men, HIV, high viral load, alcohol = more severe infection
67
Q

Presentation of Hep C

A
  • Most acute infections asymptomatic
  • 10% have mild flu-like illness
  • Jaundice
68
Q

Investigations for Hep C

A
  • HCV antibody = Present with 4-6 weeks
    o False negative in immunosuppressed and in acute infection
  • HCV RNA = current infection
  • Rise in aminotransferases
  • Fibroscan for cirrhosis
  • Ultrasound for hepatocellular carcinoma
69
Q

Management of Hep C

A
  • Acute HCV = conservative if viral load falling
  • If HCV RNA doesn’t decline then SC Pegylated interferon-alpha 2A/B + oral ribavirin
  • Interferon based drugs have many mental side effects so direct acting antiviral treatment without interferon better
  • Triple therapy with direct acting antivirals (oral)
    o NS5A inhibitor = ledipasvir
    o NS5B = sofosbuvir
70
Q

Prevention of hep C

A
  • No vaccine
  • Previous infection doesn’t confer immunity = re-infected
  • Screen blood products
  • Precaution when handling body fluid
  • Lifestyle modification = needle exchanges
  • Treatment and cure of ‘transmitters’
71
Q

Hep E

A

RNA virus transmitted by faecal oral route usually spread by contaminated water, rodents, dogs and pigs

72
Q

Risk factors for meningitis

A
  • Immunocompromised  renal failure
  • Extremes of age
  • Pregnant
  • Bacterial endocarditis
  • Crowding
  • Diabetes
  • Malignancy
  • IV drug abuse
73
Q

Causes of meningitis

A
  • Adults and children
    o Neisseria meningitides = gram-neg diplococci
    o Streptococcus pneumonia
    o Haemophilus influenza
  • Pregnant women/older adults  Listeria monocytogenes
  • Neonates  E.coli, Group B haemolytic streptococcus
  • Immunocompromised
    o Cytomegalovirus
    o Crytococcus neoformans
    o TB
    o HIV
    o Herpes simplex virus
  • Other viral causes: non-polio enteroviruses, mumps, measles
74
Q

Presentation of meningitis

A
  • Triad = Headache, neck stiffness and fever
  • Acute bacterial infection
    o Onset typically sudden
    o Intense malaise, fever, rigors, severe headache, photophobia and vomiting = within hrs/mins
    o Patient irritable and prefers to lie still
    o Papilloedema
    o Positive Kernig’s and Brudzinski’s sign can appear within hrs
    o Non-blanching petechial + purpuric skin rash = meningococcal septicaemia
    o Altered mental state with high fever = often absent
    o Neonates = hypotonia, poor feeding, lethargy, hypothermia, bulging fontanelle
  • Viral meningitis
    o Benign, self-limiting condition lasting 4-10 hrs
    o Headache may follow for some months
    o Photophobia
    o Confusion
75
Q

Investigations for meningitis

A
  • Blood cultures before lumbar puncture
  • Lumbar puncture at L4
    o If unable to perform within 30 mins give empirical antibiotics
    o Can give headache, paresthesia, CSF leak and damage to spinal cord
    o <1m presenting with fever
    o 1-3m with fever and unwell
    o <1y with unexplained fever and other features of serious illness
  • CT pre LP = Focal neurological signs
  • Blood tests = FBC, U+Es, CRP, serum glucose
  • Throat swabs
  • Pneumococcal and meningococcal serum PCR
  • If there is non-blanching petechial or purpuric rash = meningococcal septicaemia
    o No lumbar puncture due to risk of coning of cerebellar tonsils and raised ICA
76
Q

Management of meningitis

A
  • If suspect bacterial meningitis, start antibiotics before tests come back
  • Community  IM/IV benzylpenicillin, transfer to hospital
  • Bacterial meningitis
    o IV ceftriaxone or IV cefotaxime
    o If under 3m/over 50/immunocompromised then add IV amoxicillin = Listeria
    o Oral dexamethasone for 4 days = reduce cerebral oedema, hearing loss
    o Consider IV vancomycin in returning travellers or penicillin resistant
    o Meningitis septicaemia = IV benzylpenicillin
77
Q

Prophylaxis for contacts of meningitis

A

o Oral ciprofloxacin state = all ages and pregnancy
o Oral rifampicin = all ages but not pregnancy

78
Q

Complications of meningitis

A
  • Hearing loss
  • Seizures and epilepsy
  • Cognitive impairment and learning disability
  • Memory loss
  • Focal neurological deficits = limb weakness and spasticity
79
Q

Normal CSF fluid from LP

A

Clear
Protein 0.2-0.4
Glucose 0.6-0.8
WCC <5
Culture neg

80
Q

Bacterial CSF fluid in LP

A

Cloudy
>1.5g/L
Glucose <0.5
WCC >1000 + neutrophils
Bacterial culture

81
Q

Viral CSF in LP

A

Clear
Mildly raised/normal protein
Normal glucose
WCC >1000 + lymphocytes
Negative culture

82
Q

What is encephalitis

A

Infection and inflammation of brain parenchyma (frontal and temporal lobes)

83
Q

Causes of encephalitis

A
  • Herpes simplex virus 1 (children)
  • HSV 2 (neonates)
  • Varicella zoster,
  • EBV,
  • Cytomegalovirus,
  • HIV,
  • Polio, mumps, measles, rubella
  • Non-viral = Bacterial meningitis, TB, Malaria
  • Autoimmune
83
Q

Presentation of encephalitis

A
  • Triad = fever, headache and altered mental status
  • Altered consciousness
  • Altered cognition
  • Unusual behaviour
  • Acute onset of focal seizures
  • Myalgia, fatigue, nausea
  • History = Travel, Animal bite
  • Focal neurological deficit = Hemiparesis and dysphasia
  • Raised ICP and midline shift may occur resulting in coning
  • Coma
84
Q

Investigations for encephalitis

A
  • Lumbar puncture = CSF for viral PCR (elevated lymphocytes)
  • MRI after LP
    o Shows areas of inflammation and swelling, generally in temporal lobes in HSV encephalitis
    o May be midline shifting due to raised ICP
  • CT head if LP contraindicated = GCS <9, haemodynamically unstable, active seizures, post-ictal
  • Electroencephalography = Shows periodic sharp and slow wave complexes
  • Throat and vesicle Swabs  identify causative organism
  • HIV testing
85
Q

Management of encephalitis

A
  • Immediate treatment with anti-viral before results=
    o IV acyclovir = HSV, VSV
    o IV ganciclovir = cytomegalovirus
  • Anti-seizure medication = primidone
  • If meningitis suspected = Emergency IM benzylpenicillin
  • Repeat lumbar puncture
  • Other viral causes  supportive management
86
Q

Complications of encephalitis

A
  • Lasting fatigue and prolonged recovery
  • Change in personality or mood
  • Changes to memory and cognition
  • Learning disability
  • Headaches
  • Chronic pain
  • Movement disorders
  • Sensory disturbance
  • Seizures
  • Hormonal imbalance

Finals (23 decks)

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