Infection + immunity Flashcards
What type of infection is a febrile 2 month old infant likely to have?
bacterial
passive immunity to viral infection from mothers
septic screen
IV abx
What are risk factors for infection?
unwell contacts
travel to regions with endemic contagious disease
contact with animals
What are Red Flags signs of infection?
38 3-6 months, T >39 pale, mottled, blue skin reduced consciousness, neck stiffness, bulging fontanelle, status epilepticus, focal neuro signs, seizures significant resp distress bile stained vomit severe dehydration/shock
What comprises a septic screen?
blood culture, FBC, CRP, ESR, albumin, urine dip, M,C + S
consider:
CXR, LP, meningo/pneumococcal PCR, viral PCR
rapid antigen screen
What can cause encephalitis?
direct neurotoxic virus invasion of the cerebrum e.g. HSV
disordered neuro-immuno response to viral antigen e.g. post infectious encephalopathy
slow virus infection e.g. HIV or SSPE after measles
What are the consequences of HSV encephalitis?
severe neuro sequelae
focal changes seen on EEg and CT/MRI, oft temporal lobes
IV aciclovir given to all children with encephalitis
proven cases treated for 3 wks
How does Toxic Shock Syndrome present?
fever > 39
hypotension
diffuse erythematous macular rash
What causes TSS?
toxin producing Staph aureas and GpA strep
infection at any site
toxin acts as superantigen
What is the treatment for TSS?
ABC: resucitate/stabilise
3rd gen cephalosporin: ceftriaxone + clindamycin
acts on bacterial ribosome to switch off toxin production
PICU
surgical debridement
IVIg to neutralise circulating toxin
1-2 wks after onset: desquamation of hands and feet
What is PVL-producing staph aureas?
recurrent skin/soft tissue infection
necrotising fasciitis
necrotising haemorrhagic pneumonia
PVL toxin -> procoagulant state venous thrombosis
What is necrotising fascitis / cellulitis?
severe subcutaneous infection which travels along tissue planes large poorly perfused necrotic areas of tissue severe pain systemic illness staph aureas / Gp A strep \+- syndergistic anaerobe IV abx + aggressive surgical debridement IVIg
meningococcal meningitis
lowest risk of long term neuro sequelae
septicaemia + purpuric rash
non -blanching, irregular, necrotic centre
when extensive = purpura fulminans
pneumococcal meningits
high morbidity and mortality
seen in young infants
poor immune response to encapsulated organisms
hyposplenic children req daily prophylactic penicillin
What infections can haemophilus cause?
otitis media pneumonia epiglottitis cellulitis osteomyelitis septic arthritis
How do superantigens work?
usually antigens stimulate ony a small subset of T cells with a specific receptor
superantigens bind to receptors that many T cells share
->massive T cell proliferation and cytokine release
What is impetigo?
localised, highly contgious staph or strep skin infection
more common with pre existing skin disease
lesions usually on face, neck and hands
confluent honey crusted lesions
spreads readily via autoinnoculation of infected exudate
How do you treat impetigo?
topical abx e.g. mupirocin if mild
narrow spec abx e.g. flucloxacilling if severe
better adherence with co-amoxiclav
erradicate nasal carriage with nasal cream containingmupirocin or chlorhexidine + neomycin
What is a boil?
staph aureas infection of a hair follicle/sweat gland
systemic abx/occasionally surgery
persistent boils usually due to nasal carriage/family resevoir
rarely indication of immune deficiency
what is periorbital cellulitis?
fever, with erythema, tenderness and oedema of the eyelid
unilateral
if unimmunised - H influenzae b!
due to local trauma or spread from paranasal sinus/dental abscess
How would you manage periorbital cellulitis?
prompt IV abx
to prevent posterior spread and orbital cellulitis
What are the signs of orbital cellulitis?
proptosis painful, limited occular movement reduced visual accuity complications inc abscess, meningitis, cavernous sinus thrombosis
How would you manage orbital cellulitis?
CT scan: assess posterior spread
LP: exclude menigitis
What is scalded skin syndrome?
exfoliative staphylococcal toxin
fever, malaise, purulent crusting around face, widespread erythema and tenderness of skin
Nikolsky sign: areas of skin separate on gentle pressure
= denuded areas of skin
How would you manage SSS?
IV anti-staph abx
analgesia
monitoring fluid balance
What is HSV?
Viral infection initially of mucous membranes or skin causing intense local mucosal damage
HSV1: lip
HSV2: genital
mostly asymptomatic
What is aciclovir
viral DNA polymerase inhibitor used to treat severe HSV infection
Gingivostomatitis
10 months - 3 years
vesicular lesions on lips, gums, tongue, hard palate
-> extensive painful ulceration with bleeding
high fever
2 wk duration
symptom management - dehydration a concern
What is a herpetic whitlow?
HSV
painful, erythematous, oedematous, white pustules on the site of broken skin on the fingers
spread by autoinoculation from gingivostomatitis or from lips of infected parents
What is eczema herpeticum?
serious
widespread vesicular lesions develop on eczematous skin
can be complicated by secondary bacterial infection and result in septicaemia
Can HSV afeect the eyes?
Yes
it can cause blepharitis or conjunctivitis
may extend to involve the cornea
can cause scarring and loss of vision
if herpetic lesions are near the eye opthalmic investigation of the cornea by slit lamp is req
How are neonates affected by HSV?
infection can be focal or widely disseminated.
skin and eyes usually affected
encephalitis can occur
morbidity and mortality are high
What are the complications of VZV?
Secondary staph/GpA strep Infection, may -> TSS/nec fasc
consider where onset of new fever or persistent high T after first few days
Encephalitis generalised, e\arly days of illness, gd prognosis
mostly VZV assoc cerebellitis
usually occurs 1 wk after onset of rash
child is ataxic with cerebellar signs
Purpura Fulminans:
production of antiviral antibodies may cross react and inactivated protein S -> dysreg of fibrinolysis and incr clotting
Disseminated Disease:
may occur in immunocompromise
vesicular erruptions persist and become haemorrhagic 20% mortality
What is EBV
virus transmitted by oral contact
majority = subclinical
can -> infectious mononucleosis syndrome
involved in pathogenesis of:
Burkitts lymphoma
lymphoproliferative disease in the immunocompromised and naopharyngeal carcinoma
How might children with infectious mononucleosis syndrome present?
fever
malaise
tonsillopharyngitis
lymphadenopathy
(petechiae on soft palate, splenomegaly, hepatomegaly, mac-pap rash, jaundice)
How do you diagnose infectious mononucleosis syndrome?
blood film: atypical lymphocytes - numerous large T cells
+ve monospot test
Igm + IgG to EV antigens
What is infectious mononucleosis syndrome?
immune response to EBV
can last up to 3 months
treatment is symptomatic
e.g. corticosteroids may be req in case of airway compromise
Why should you not give ampicillin or amoxicillin in cases of suspected EBV?
it will cause a florid maculopapular rash
What is CMV?
virus transmitted in bodily fluids
usually mild/subclinical infection
most infected by 2 yrs
an issue in the immunocompromised and the fetus
Fetal: deafness, IUGR, hydrocephalus, thrombocytopenia
What precautions are taken to avoid CMV transmission in those undergoing transplantation?
CMV -ve blood
anti-CMV prophylaxis
don’t transplant CMV +ve organs
What effects can CMV have in the immunocompromised ?
retinitis pneumontis bone marrow failure encephalitis hepatitis colitis oesophagitis
How is CMV treated?
ganciclovir
foscarnet
What is exanthem subitum?
2yrs aka roseola infantum high fever + malaise for a few days generalised macular rash rare -req serological confirmation HHV6 or 7 commonly causes febrile convulsions
What illnesses can parvovirus B 19 cause?
Asymptomatic infection
Erythema Infectiosum: aka
slapped cheek/fifth disease
transmission: resp secretions/vertical/blood
fever, malaise, headache, myalgia, facial rash
Aplastic crisis: in children with chronic haemolytic anaemias causing incr RBC turnover or immunosuppressed
Fetal disease:
vertical transmission -> fetal hydrops + death
What clinical syndromes are caused by enteroviruses?
mostly cause asymptomatic/self-limiting illnes with rash (purpuric)
hand, foot and mouth disease herpangina aseptic meningitis pleurodynia myocarditis/pericarditis
What is Guillaine-Barré syndrome?
Acute post infectious polyneuropathy 2-3 wks after URTI or campylobacter Ascending symmetrical weakness Autonomic dysfunction (urinary retention, will req cath) Depression of respiration (measure vital cap + peak flow, may req vent) Arreflexia CSF protein raised Max weakness 2-4 wks after onset Supportive treatment
What is haemolytic uraemic syndrome and how does it present?
Hx of gastroenteritis infection (e.coli) Oliguria Oedema Petechiae Pallor (jaundice) AKI + fluid overload = severe htn, HF, convulsions
How to treat malaria
Evidenc of ruptured spleen -
Salmonella typhi
Rose spots !!!
SCID
Low B cells
Low Ig
Low T cells
Hyper IgM
CD40 ligand defect
Recurrent infections
Normal B cells
Normal T cells
Bruton’s agammaglobulinaemia
Normal T cells
Low B cells
Low Ig
Predisposition to Resp and CNS infections
Thymic absence/ hypoplasia
No T cells
Normal B cells
Normal Ig
Risk from encapsulated organisms: strep pneumoniae, haemophilus influenzae
Complement deficiency: c3
Recurrent pyogenic infection
Complement deficiency: c1, c2, c4
Autoimmune issues
Complement deficiency: c5-9
N.meningitidis
Infection risk in the immunocompromised (HIV, steroids, chemo)
TB Pneumocystis jiroveci (PCP)
Opportunistic infection prevented by prophylactic septrin post transplant
Pneumocystis jiroveci
Pos transplant infection risks
CMV
VZV
Fungal:
Drugs used for immunosuppression post transplant
Tacrolimus
Ciclosporin
Mycophenolate mofetil
Fifth disease
Aka slapped cheek
Aka erythema infectiosum
Aka parvovirus
Slapped cheek appearance -> macpap rash on limb
Malaise + fever
Complications incl: arthralgia + aplastic anaemia
Do FBC to rule out aplastic crisis
VZV
Aka chicken pox
14-21 day incubation
Rash on trunk + scalp: vesicles + pustules
Fever
Complications incl: encephalitis(ataxia), pneumonitis, conjunctival lesions
More dangerous with concurrent eczema
Measles
1-12 day incubation
Lethargy, fever, cough, coryza, conjunctivitis
4 days later Macular rash starts on face -> trunk
Koplik’s spots in mouth
Complications incl: pneumonia, otitis media, encephalitis
Scarlet fever
Gp A beta-haemolytic strep
Tonsillitis
7 day incubation
Erythematous rash, mostly on trunk
Strawberry tongue + desquamation
Complications incl: otitis media, rheumatic fever, acute nephritis
Diagnosis: raised ASOT titres, gp A strep on throat swab
Roseola infantum
Aka exanthema subitum
HHV 6+7
High fever malaise
Generalised macular rash
Ddx on finding evidence of virus in serum
Kawasaki
Childhood vasculitis, most
Managing giardiasis
Oral metronidazole
Mumps
Paramyxovirus
Droplet spread in pre adolescents
Parotitis and constitutional sx
Complications: orchitis, meningitis, pancreatitis
Management: bed rest, scrotal support, analgesia
Orchitis -> testicular atrophy in 50%, bilat = infertility
Diphtheria
Flu like illness + neck swelling Sore throat with grey slough covering mucosa of pharynx and tonsils Corynebacterium diptheriae G+ve anaerobe \+ demonstration of toxin req for Dx Toxin can cause sever hypotension
Quinsy
Aka peritonsillar abscess
Unwell
Severe dysphagia, earache, trismus(lockjaw)
Unilat bulge of soft palate with deviation of uvula to opposite side
Inflamed tonsils + halitosis
Rupture of the abscess can result in aspiration pneumonia
Tetanus
G+ve Anaerobe clostridium tetani Neurotoxin= tetanospasmin Acts on motor cells of CNS Signs: trismus (lockjaw), risus sardonicus (grinning face), opisthotonus (arched body + hyperextended neck), autonomic dysfunction (tachycardia, arrhythmia, low bp, sweating) Anti-tetanospasmin Ig
Poliomyelitis
RNA poliovirus
Ant horn cells of lower motor neurones
Flu like illness, muscle pain, flaccid paralysis, areflexi
Pertussis
Aka whooping cough
Bordetella pertussis
Coryza, dry cough, becomes paroxysmal
No treatment
Complications incl pneumonia + bronchiectasis
