Infection and Immunity Flashcards
Red flags in infection
Fever >38’c (<3 months) >39’c (3-6 Months)
Pale, mottled, cyanosis
Reduced consciousness: does not wake or remain awake when roused
Bulging fontanelles
Neck stiffness
Status epilepticus
Focal neurology
Severe dehydration/shock: reduced skin turgor, tachycardia, < cap refill, dry mucous membranes, poor feeding
Bile stained vomit
Significant respiratory distress: grunting, tachypnoea (RR>60), moderate or severe chest indrawing
No response to social cues
Weak, high-pitched or continuous cry
Mx sepsis
Ceftriaxone, IV fluids
Correction of clotting in DIC: FFP, cryoprecipitate, platelet transfusion
Causative organisms sepsis
Associated with staph aureus or staph pneumonia in children
In neonates group B stress or E.coli
Features bacterial meningitis
Usually follows bacteraemia
Release of inflammatory mediators and activated leukocytes cause cerebral odea, and fibrin deposits block resorption of CSF
Causative organisms bacterial meningitis
Neonates: GBS, E.coli, Listeria
1month-3 months: Neisseria meningitidis, strep pneumonia, H. influenza
>6 years: N. meningitidis, step pneumonia
Mx bacterial meningitis
Administer antibiotics and supportive therapy: third gen cephalosporin
Prophylaxis rifampin or ciprofloxacin given to eradicate nasal carriage in household contacts and vaccination against Men C
Causative organism viral meningitis
Usually enterovirus, EBV, adenovirus and mumps
Atypical organisms meningitis
Mycoplasma, borrelia bordefei, TB, fungal infection
Usually in immunodefiency
Features encephalitis
nflammation of the brain substance
Most commonly enterovirus, respiratory virus and herpes virus
High dose acyclovir given to all in case of HSV encephalitis
HSV encephalitis:
-Rare cause
-Detected by PCR
-CT/MRI shows focal lesions due to the destructive nature of virus
-High mortality with severe neurological sequelae
Mx toxic shock syndrome
Usually requires ICU to managed shock
Areas of infection need surgical debridement
Third cephalosporin antibiotics to switch of bacterial toxin production
IVIg can be used to neutralise circulation toxin
Features toxic shock syndreom
Toxin producing bacteria: staph aureus, group A strep
Characterised by: fever over 39’c, hypotension, diffuse erythema, macular rash
Multiple organ dysfunction
Desquamation of palms and soles can occur 1-2 weeks following onset of illness
Features necrotising faciitis
Severe cutaneous infection involving skin place to fascia/muscle
Typically staph aureus or group A strep
Severe pain and systemic illness
Usually requires ICU
IV antibiotics are not sufficient alone
Surgical intervention and debridement of necrotic tissue
Features Kawasaki
Systemic vasculitis: requires immediate treatment
Affects children aged 6 months- 4yars with peak onset at year 1
More common in Japanese and Balck carribean origin
Typically high fever over 5 days resistant to antipyretics
Conjunctival injection, bright red/cracked lips, strawberry tongue, cervical lymphadenopathy, red palms on hands and soles of feet
Clinical diagnosis, no specific testing
Mx Kawasakis
High dose aspirin: reduces thrombosis, given until the fever subsides and inflammatory markers return to normal
Lower dose given for 6 weeks after normal echo
IVIg given within first 10 days
Echocardiogram: screening for coronary artery aneurysm (giant aneurysm requires warfarin)
Presentations of staph
Impetigo Boils Periorbital cellulitis Orbital cellulitis Staphylococcal scalded skin syndrome
Presentations of H. influenzae
otitis media, pneumonia, epiglottitis, cellulitis, osteomyelitis, septic arthritis
Presentations of pneumococcus
pharyngitis, otitis media, conjunctivitis, sinusitis
Features herpes virus infection
gastroenteritis, cold sores, eczema herpeticum, herpetic whitlows (edematous white pustules, typically on finger), eye disease, dissemination
Features chicken pox
Common skin condition of childhood with characteristic rash and prodrome including fever, headache, malaise, abdominal pain
Self resolving in most children
Prophylaxis indications chicken pox
IV acyclovir and IVIg in immunocompromised and pregnancy with exposure to children
Features EBV
Tropism for B lymphocytes and epithelial cells of the oropharynx
Oral transmission
Fatigue prominent feature
Fever, malaise, tonsillitis, pharyngitis, lymphadenopathy, petechiae, splenomegaly, hepatomegaly, maculopapular rash, jaundice
Long course typically 1-3m
Mx EBV
Symptomatic treatment
Corticosteroids given where airway is compromised
Group A strep commonly concurrent- penicillin
Avoid amoxicillin and ampicillin which can cause a florid maculopapular rash
Ix EBV
Blood film shows atypical lymphocytes and numerous large T cells
Monospot test positive (Poor sensitivity)
Seroconversion with antibodies
Features CMV
subclinical in most immunocompetent hosts
Mx CMV
IV ganciclovir and valganciclovir
Used as prophylaxis in immunocompromised .e.g. transplant
Features HPV B19
Causes slapped cheek syndrome
Commonly occurs in outbreaks typically in the summer
Effects erythroblastosis red cell precursors in bone marrow
Multiple clinical syndromes: erythema infectiosum; aplastic crisis;fetal disease
Features mumps
Replicated in epithelial cells: access to parotid via widespread dissemination
Fever, malaise, parotitis often unilateral and becomes bilateral
Can cause orchitis especially in post pubertal males: unilateral hence infertility is uncommon
Transient hearing loss associated
Pancreatic involvement causes abdo pain
Features tuberculosis
Latent disease is asymptomatic: more likely to progress to active disease in children
Local inflammatory responses typically limits progression of infection
Lymphatic spread occurs in failure of immune response in children, causing systemic symptoms of fever, anorexia, weight loss, cough
Ix Tuberculosis
Sputum sample difficult to acquire in children <8years of age
Gastric washing can be used to collected swallow septum in children
Culture shows acid fast bacilli and PCR
Mantoux test positive for previous infection and vaccination
Induration of 5mm is positive of active TB regardless of previous vaccination
ChestXray shows hilar lymphadenopathy, collapse and consolidation/pleural effusion
Mx tuberculosis
Quadruple therapy: rifampicin, isoniazid, pyrimidine, ethambutol for 2 months then decreasing to rifampicin and isoniazid for 4 months
Pyridoxine is given weekly in adolescents to prevent peripheral neuropathy associated with isoniazid
BCG vaccination for high risk individuals only
Dexamethasone given in meningitis
Latent TB in children can be treated prophylactically to decrease reactivation in later life
Features rheumatic fever
Rare in developed world
Response to group A beta haemolytic strep
Affects children aged 5-15
Prevention by use of antibiotics for 10 days in initial strep infection
Latent period of 2-6 weeks
Main manifestations:
-Endocarditis
-Myocarditis and heart failure
-Pericarditis (friction rub, effusion, tarde)
-Sydenham Chorea
-Migratory arthritis: ankles, knees and wrists
-Erythema Marginatum: rash on trunk and limbs
-Subcutaneous nodules: extensor surfaces
Heart disease is often long term damage from scarring and fibrosis of valvular tissue- associated with mitral stenosis developing in adult life
Ix Rheumatic fever
GAS titre including culture or antigen- raised in acute phase
Prolonged PR interval on ECG
Mx Rheumatic fever
Bed rest and anti-inflammatories
High dose aspirin effective in suppression of inflammatory responses
Corticosteroids for non-resolving fever and inflammation
Heart failure controlled by diuretics and ACE inhibitors
Recurrence prevented by daily oral penicillin or monthly injection of benzylpenicillin (erythromycin in penicillin allergy)
Prophylaxis given for 10 years post infection or until age 21
Topical infections examples
Malaria Typhoid Dengue Chiniingiya Zika virus Viral haemorrhagic fever
Examples T cell defects
Severe combined immunodeficiency Wiskott Aldrich syndrome DiGeorge Duncan disease Ataxia telangiectasia
Features T cell defect immunodeficiency
Severe and unusual viral and fungal infection and faltering growth in the first few months
Abnormal FBC and lymphocyte subsets
Mx T cell immunodeficiency
Cotrimoxazole to prevent PCP and itraconazole/fluconazole to prevent fungal infection
Features wiskott aldrich syndrome
Triad of immunodeficiency, thrombocytopenia and eczema
X linked
Features Duncan disease
poor response to EBV
Susceptible to lymphoma
Features ataxia telangiectasia
Defect in DNA repair
Increased risk of lymphoma
Cerebellar ataxia
Developmental Delay
Dx HIV
Diagnosis is by antibody detection in children over 18 months
Before 18 months, maternal IgG is present: HIV PCR is diagnostic test
2 negative tests within first 3 months confirms lack of HIV
Mx HIV
All children followed up with ART following diagnosis
Prophylaxis for PCP given in low CD4 count
Reduction in vertical transmission during pregnancy by good regimen HAART and no breastfeeding, good labour management including possible C section
Childhood presentation HIV
Mild: lymphadenopathy or parotid enlargement
Moderate: recurrent bacterial infections, candidiasis, chronic diarrhoea, lymphocytic interstitial pneumonitis
Severe: opportunistic infections, severe growth faltering, encephalopathy, malignancy
Features B cell immunodeficiency
In first 2 years severe bacterial infections, especially hearts, sinus, pulmonary, and skin infections.
Recurrent diarrhoea and faltering growth
Immunoglobulin levels and subclasses
Mx B cell deficiency
Antibiotic prophylaxis .e.g. Azithromycin to prevent recurrent bacterial infections
Examples B cell defects
X-linked ammaglobulinaemia
Common variable immune deficiency
Hyper IgM syndrome
Selective IgA deficiency
Features leukocyte function defects
Delayed separation of the umbilical cord, delayed wound healing, chronic skin ulcers, deep-seated infections
Leukocyte adhesion deficiency: Deficiency of neutrophil surface adhesion molecules causes inability of neutrophils to migrate to sites of infection and inflammation
Features Complement Defects
Recurrent bacterial infections
SLE like illness
Recurrent meningococcal, pneumococcal and H.influenzae infection
E.g. Early complement component deficiency, terminal complement component deficiency, mannose-binding lectin deficiency
Ix complement defects
Tests of classical and alternative complement pathways, mannose binding lectin levels and assay for individual complement proteins.
dDx infectious rashes
Chicken pox Measles Rubella Erythema Infectiosum Scarlet fever Hand, foot, and mouth
Features chicken pox rash
Initially a fever
Itchy rash, starting on head/trunk before spreading.
Initially macular then popular than vesicular
Systemic illness usually mild
Features Measles
Irritable, conjunctivitis, fever prodrome
Koplick spots: white spot on buccal mucosa
Rash starting behind ears spreading to whole body
Discrete maculopapular rash become blotchy and confluet
Features Rubella
Pink maculopapular initially on face before spreading to whole body
Usually afdes by day 3-5
Lymphadenopathy affecting suboccipital and postauricular
Features Erythema Infectiosum
Slapped cheek syndrome
Associated with parvovirus B19
Lethargy, fever, headache, , cheek rash spreading to arms and extensor surfaces
Feasture Scarlet fever
Group A haemolytic streptococci
Fever, malaise, tonsillitis, strawberry tongue
Rash is fine punctate sandpaper rash sparing around the mouth (circumoral pallor)
Features hand foot and mouth
Coxsackie A16 virus
Mild systemic upset of sore throat and fever
Vesicles in the mouth and on palms and soles of feet
