Infection/Immunology Flashcards
What organisms cause bacterial meningitis by age?
Neonate-3m
- GBS
- E.Coli/ other coliforms
- Listeria
1m-6y
- N meningitidis
- Strep pneumoniae
- HiB
> 6y
- N meningitidis
- Strep pneumoniae
What pathogen is meningococci?
Neisseria Meningitidis
What does meningococcal disease cause?
Meningitis 30-50%
Septicaemia 7-10%
Both 40%
- Neurological consequences in 10%
Peak incidence of meningococcaemia?
6-24m
Meningitis vaccination schedule?
Men B –> 8w, 16w, 1y
Men C –> discontinued 2016
Men A –> 14y (Men ACWY)
In UK which N meningitides most common?
Men B - vaccine not that effective
Features of meningitis? (many)
- Fever
- Headache
- Photophobia
- Neck stiffness
- Lethargy
- Poor feeding/vomiting
- Irritability
- Hypotonia
- Drowsiness
- Loss of consciousness
- Seizures
- Petechiae rash
- → Can be v non-specific in young children/ early stages
Features of meningoccaemia?
→ Signs of shock
- Tachycardia
- Tachypnoea
- Prolonged cap refill
- Hypotension
- Cold extremities
- PURPURIC RASH
Features of a purpuric rash? (3)
- Non-blanching on palpation
- Irregular in size and outline
- Necrotic centre
What management if child with purpuric rash + fever?
Immediate systemic IV/IM abx eg benzylpenicillin
Immediate transfer to hospital
Ddx for purpuric rash? (3)
- Infections → septicaemia, measles, other meningitis
- Immune causes → HSP, SLE, RA
- Thrombocytopaenic → leukaemia, aplastic anaemia, immune thrombocytopaenia, DIC, HUS
Ix if petechial rash + fever?
- FBC
- CRP
- Coagulation screen
- Blood culture
- Whole body PCR for N. Meningitidis
- Blood glucose
- Blood gas (for acidosis)
- U&Es, LFTs
- Culture of blood, throat, urine, stool
- LP unless CI (raised ICP, shock)
- Consider CT/MRI and EEG
Which abx to give in confirmed meningococcal disease?
IV ceftriaxome for 7d
Immediate complications of meningococcaemia?
- DIC
- Coma
- Thrombocytopaenia
- Septic arthritis
- Bacterial endocarditis
- Peripheral gangrene
Long term complications for meningococcaemia?
- Hearing loss
- Orthopaedic - damage to bones and joints
- Skin complications (inc scarring from necrosis)
- Psychosocial problems
- Neurological and developmental problems
- Renal failure
Commonest pathogen overall in sepsis in children?
N Meningitidis
Common pathogens in sepsis in neonates?
Early onset (<48h) → from mother/birth canal
- GBS
- E Coli
- Coagulase negative staph
- H influenza
- Listeria monocytogenes
Late onset (4-90d) → from environment:
- Coagulase negative staph
- S. Aureus
- E. Coli
- Klebsiella
- Pseudomonas
- Candida
Sepsis sx?
- Fever
- Poor feeding
- Miserable, irritable, lethargy
- Hx of focal infection, e.g. meningitis, osteomyelitis, gastroenteritis, cellulitis
- Predisposing conditions, e.g. sickle cell disease, immunodeficiency
Signs of sepsis?
- Fever
- Tachycardia, tachypnoea, low BP
- Purpuric rash (meningococcal septicaemia)
- Shock → delayed cap refill, widened pulse pressure
- Multi-organ failure
Normal pulse rate by age?
<1y –> 110-160
1-5y –> 95-140
5-12y –> 80-120
>12y –> 60-100
Upper limit of SBP for
a) 1-5y
b) 6-10y
a) <110mmHg
b) <120mmHg
Clinical features of shock?
Early (compensated)
- Tachypnoea
- Tachycardia
- Decreased skin turgor
- Sunken eyes and fontanelle
- Delayed capillary refill (>2 s)
- Mottled, pale, cold skin
- Core–peripheral temperature gap (>4°C)
- Decreased urinary output
Late (decompensated)
- Acidotic (Kussmaul) breathing
- Bradycardia
- Confusion/depressed cerebral state
- Blue peripheries
- Absent urine output
- Hypotension
Empirical abx for suspected sepsis in
a) <8w
b) >8w
a) ampicillin + gentamicin/cefotaxime/ceftriaxone
b) 3rd gen cephalosporin - cefotaxime/ceftriaxone
Initial fluid resus in shock?
0.9% saline or blood
20ml/kg
Give 2x if necessary
2 types of allergic reactions?
Non-IgE mediated
- Reflux, tummy pain, eczema, diarrhea
- Delayed onset and variable clinical presentation
IgE mediated (T1 hypersensitivity)
- Swelling, urticarial, angioedema, sneezing, bronchospasm, anaphylaxis
- Early phase → caused by histamine release and other mediators from mast cells → urticaria, angioedema, sneezing and bronchospasm
- Late phase → 4-6 hours later with nasal congestion in upper airway and cough and bronchospasm in lower airway
Pathophysiology of IgE mediated allergic reaction?
Sensitisation:
- Antigen of allergen taken up by antigen-presenting cell
- Antigen is presented on class II MHC to T helper cells
- T cell produces cytokines to cause B cells to proliferate and differentiate into IgE-producing plasma cells
- IgE molecules attach via constant regions to Fc receptors on mast cells
- Once attached IgE molecules can survive for weeks
- → Now sensitized
Reaction
- When exposed to antigen 2nd time, antigen binds to IgE antibodies on mast cells
- To trigger response, 2 IgE molecules must interact with specific antigen
- This → release of histamine and other inflammatory mediators
- → Capillary dilation, airway constriction, mucus secretion, pain, itching
Management strategies for allergies? (4)
- Antihistamines
- Steroids
- Epipen provided for anaphylaxis
- Possibly systemic desensitisation
How does HIV present when there is mild immunosuppression?
- Lymphadenopathy
- Parotitis
How does HIV present when there is moderate immunosuppression?
- Recurrent bacterial infections
- Candidiasis
- Chronic diarrhea
- Lymphocytic interstitial pneumonitis (LIP)
- → This lymphocytic infiltration of lungs may be caused by a response to HIV infection itself, or may be related to EBV infection
Name some severe AIDs defining diagnoses?
- Opportunistic infections, e.g. Pneumocystis jiroveci (carinii) pneumonia (PCP)
- Severe FTT
- Encephalopathy
- Malignancy → rare in children
- > 1 clinical feature often present
- Unusual constellation of symptoms, esp if infectious, should alert one to HIV infection
What interventions are used to reduce mother-baby transmission of HIV?
- Use of maternal antenatal, perinatal and postnatal ARVs to achieve undetectable maternal viral load at time of delivery
- Avoidance of breastfeeding
- Active management of labour and delivery, to avoid PROM or unnecessary instrumentation
- Prelabour C- section if mother’s viral load detectable close to delivery
Management of HIV?
Drugs:
- As in adults, 3 or 4 dugs used
- PCP prophylaxis with co-trimoxazole given to all infants with HIV or older children with low CD4
Other aspects:
- Immunisation → give all routine but not BCG (live), also give additional against influenza, Hep A, B and varicella
- MDT management with family to ensure compliance and planning for future
- Regular follow up – weight, neurodevelopment, clinical S+S of disease
Clinical features of infectious mononucleosis?
- Fever
- Malaise
- Tonsillopharyngitis – often severe, limiting oral ingestion of fluids and food; rarely, breathing compromised
- Lymphadenopathy – prominent cervical lymph nodes, often diffuse adenopathy
- Fatigue
Treatment of infectious mononucleosis?
- Symptomatic
- When airway severely compromised, corticosteroids considered
- In 5%, group A strep grown from tonsils
- → May be treated with penicillin
- Ampicillin or amoxicillin may cause florid maculopapular rash in children infected with EBV and should be avoided
Complications of infectious mononucleosis?
- Prolonged fatigue (>6m) → >1/10 pts
- Anaemia/neutropenia/ thrombocytopenia
- Ruptured spleen – 1/500-1000 cases → avoid contact sports during illness
- Neurological complications →Guillain Barre, Bell’s palsy, viral meningitis, encephalitis
- Secondary infection → pneumonia, pericarditis (usually only if immunocompromised)
What is Kawasaki disease?
Systemic vasculitis (usually in <5yo)
- Specific cause unknown
- Important diagnosis b/c aneurysms of coronary arteries are potentially devastating complication
Diagnostic criteria of Kawasaki disease?
Fever (>38) ≥ 5 days duration + ≥4 of (incomplete if <4):
- Polymorphous rash (92%) – many different forms, always extensive
- Changes in extremities - eg erythema of palms/soles (80%), indurative oedema, desquamation of fingers/toes
- Bilateral non exudative bulbar conjunctivitis
- Changes in lips and oral cavity - eg dryness, erythema, fissuring of lips, strawberry tongue (71%)
- Cervical lymphadenopathy – least common
RED RED RED
Ddx of Kawasaki disease? (7)
- Viral exanthems (e.g. measles, adenovirus, enterovirus, EBV)
- Scarlet fever
- Staphylococcal scalded skin syndrome
- Stevens-Johnson syndrome
- Juvenile idiopathic arthritis (systemic onset)
- Toxic shock syndrome
- Drug hypersensitivity reactions
Diagnostic test for Kawasaki disease?
No diagnostic test
–> Clinical diagnosis
Treatment of Kawasaki disease?
- Self-limiting, treat to reduce coronary aneurysms
- Coronary arteries affected in 1/3 within 6w, aneurysms can → subsequent narrowing of vessels → myocardial ischaemia and sudden death
- Mortality = 1-2%
- IVIG given within 10d – reduce aneurysms
- Aspirin – reduce thrombosis
- If giant coronary aneurysms – may need long term warfarin
- Can use antiplatelet if severe thrombocytosis
