Infection And Immunity Flashcards
Causes and presentation of fever in less than 3 months
Often have bacterial infection because viral is rare due to passive immunity from mothers
Usually present with non-specific clinical features and fever
Need urgent investigation with septic screen and IV antibiotics
Severe fever in less than 3 months
If less than 3 months then 38 is severe
If 3-6 months then >39
Other signs of severe illness in febrile infant
Pale, blue and mottled Reduced consciousness, bulging fontanelle, neck stiffness, status epilepticus, focal neurological signs or seizures (meningitis) Significant Resp distress Bile stained vomiting Severe dehydration or shock
Which antibiotics are given to seriously unwell febrile infants
3rd generation cephalosporin eg. Cefotaxime or ceftriaxone if >3 months
If 1-3 months then cefotaxime and ampicillin
What should be given to febrile child if herpes simplex encephalitis suspected
Aciclovir
Where does most of the damage come from in bacterial meningitis? X3
From host immune response rather than organism itself
Release of inflammatory mediators and activated leukocytes, together with endothelial damage lead to cerebral oedema, raised ICP and decreased cerebral blood flow
Inflammatory response below the meninges causes vasculopathy - cortical infarction
Fibrin deposits block resorption of CSF leading to hydrocephalus
Common organisms causing meningitis in neonate-3months x3
Group b strep
E Coli
Listeria monocytogenes
Common meningitis organisms 1 month- 6 years x3
Neisseria meningitidis
Strep pneumoniae
Haemophilus influenzae
Common meningitis organisms >6 years x2
Neisseria meningitidis
Strep pneumoniae
Investigations for meningitis
Lumbar puncture for CSF FBC Coag screen and crp Blood, urine, throat swab, stool culture Blood and csf PCR
What is brudzinski sign
Sign of meningitis
Flexion of neck when supine causes knee and hip flexion
What is Kernig sign
When supine with hips and knees flexed, back pain on extension of knee
Sign of meningitis
Meningitis antibiotics
3rd generation cephalosporin eg. Cefotaxime or ceftriaxone
What can be given with antibiotics in the management of meningitis beyond neonatal period and why
Dexamethasone to reduce long term complications such as deafness
Cerebral complications of meningitis x 6
Hearing loss from inflammatory damage to cochlear hair cells
Local vasculitis causing cranial nerve damage or focal lesions
Local cerebral infarctions
Subdural effusion (esp. With haemophilius influenzae and pneumococcal)
Hydrocephalus
Cerebral abscess - suspect if clinical condition deteriorates and signs of SOL and fluctuating temperature
Most common presentation of encephalitis x3
Fever, altered consciousness and seizures
Most frequent causes of encephalitis in UK x3
Enteroviruses, resp viruses and herpesvirus
What should all children with encephalitis be treated with and why?
Aciclovir because although rare - herpes encephalitis can have devastating long term consequences
Therefore all started with high dose until herpes eliminated
Investigations for encephalitis
Same for meningitis
How long do you treat proven or highly suspicious herpes encephalitis for?
3 weeks IV aciclovir
What causes toxic shock syndrome
Toxin producing staph aureus and group a strep
Characteristics of toxic shock syndrome x3
Fever >39
Hypotension
Diffuse erythematous macular rash
What happens in toxic shock syndrome
Toxin producing bacteria released from an infection at any site including small lesions
Toxin acts as super antigen and causes organ dysfunction
Effects of toxic shock syndrome x6
Mucositis (conjunctivae, oral and genital mucosa)
GIT dysfunction (d and v)
Renal impairment
Liver impairment
Clotting abnormalities and thrombocytopenia
CNS disturbances
Management of toxic shock syndrome
Surgical debridement and antibiotics (3rd generation cephalosporin) also clindamycin - switches off toxin production by acting on bacterial ribosome
ICU to manage the shock
What happens 1-2 weeks after onset of toxic shock syndrome
Desquamation of palms, soles, fingers and toes
Complication of toxic shock syndrome causing severe problems
PVL (Panton-Valentine leukocidin) producing staph aureus causes recurrent skin and tissue infections
Can also cause necrotising fasciitis and a necrotising haemorrhagic pneumoniae following influenza type illness
What is necrotising fasciitis and management?
Infection often involving all tissue planes down to fascia and muscle
Need surgical debridement to treat
What causes meningoccoal infection and meningitis
Neisseria meningitidis
Risks associated with meningoccocal infection
Can kill within hours but out of the 3 main causes of bacterial meningitis it has the lowest risk of long-term neurological sequelae
Characteristic of meningococcal infection
Non blanching rash, irregular lesions with necrotic centre - may or may not be meningitis present
Treatment of meningococcal infection (rash)
Immediate IV antibiotics eg. Penicillin
Vaccinations against meningoccoal infection?
Against group a and c meningococcus but none against group b which causes majority of isolates in UK
What causes impetigo?
Staph aureus (both) or strep pyogenes (only non-bullous)
What is impetigo?
Highly contagious, localised skin infection - most common in infants and young children
Rapid spread via autoinoculation
When is impetigo more common?
In pre existing skin disease eg. Eczema
Features of impetigo
Non-bullous - Lesions usually on face, neck and hands
Begin as erythematous macules that become vesicular/pustular and then rupture with exudation of fluid and get honey coloured crusted lesions
Usually asymptomatic - might be a bit itchy
Or bullous - Blisters that then burst to form crusts - less commonly affects the face (more neck folds, nappy area and axilla) painful and systemic symptoms more common
Treatment of impetigo
Non-bullous - fusidic acid TDS/QDS 7 days or oral fluclox if widespread (clarithro or erythro if pen allergic) for 7 days
Bullous - oral always needed - as above
MRSA then mupirocin
What are boils and what caused by?
Infected sweat glands or hair follicles by staph a
Treatment with systemic antibiotics and occasionally surgery
What causes peri orbital cellulitis?
Staph a or strep
Also haem influenzae type b - which may also be accompanied by other infection sites eg. meningitis
Presentation of peri orbital cellulitis
Fever with erythema, tenderness and oedema of eyelid
Management of periorbital cellulitis
Treatment with IV antibiotics to present posterior spread of infection to orbital cellulitis
CT scan to see if spread posterior
Maybe LP to exclude meningitis
Signs of orbital cellulitis
Proptosis, painful or limited eye movements and reduced visual acuity
What is scalded skin syndrome?
Staph a toxin causing separation of epidermal skin layers
Who gets scalded skin syndrome?
Infants and young children
Signs of scalded skin syndrome
Fever, malaise and may have purulent, crusting, localised infection around eyes, nose, mouth - subsequent widespread erythema and tenderness of skin
Epidermis separates on gentle pressure (Nikolsky sign) leaving denuded areas of skin which subsequently dry and heal without scar
Management of scaled skin syndrome x3
IV anti-Staph antibiotic
Analgesia
Monitor fluid balance
How accurate is axillary temp?
Generally underestimates by 0.5 degrees
How do herpes simplex viruses typically enter the body?
Through mucosal membranes or skin - site of primary infection typically has intense local mucosal damage
Where does herpes simplex 1 typically affect?
Lip and skin lesions
Where does herpes simplex 2 typically affect
Genital lesions
But both HSV can cause oral and genital lesions
Treatment of HSV
Aciclovir
Most common primary HSV infection in children
Gingivostomatitis
When does herpes gingivostomatitis typically occur?
10 months to 3 years
Presentation of herpes gingivostomatitis
Vesicular lesions on lips, gums, tongue and hard palate
Very painful and ulceration leads to bleeding
High fever and child unhappy
Decreased eating and drinking can lead to dehydration and poor nutrition
Management of herpes gingivostomatitis
Aciclovir
IV fluids and nutrition
Skin manifestation of HSV x2
Eczema herpeticum (serious condition, widespread vesicular lesions which develop on eczematous skin - can be complicated by secondary bacterial infection which may result in septicaemia) Herpetic whitlow (painful, erythematous, oedematous white pustules on site of broken skin on fingers - spread is from autoinnoculation or parents kissing children's fingers or from HSV 2 in sexually active teens)
Eye disease of HSV x4
May cause blephritis or conjunctivitis
Can extend to cornea producing dendritic ulceration
Can lead to corneal scarring and loss of vision
Clinical features of chicken pox x5
Vascular rash with 200-500 lesions that start on torso and progress to peripheries - papules then vesicules, then pustules and then crusts
Crops appear at different times for up to one week
Itchy
Complications of chickenpox x3
Secondary bacterial infection with staph or group a strep (impetigo) - can lead to further complications such as toxic shock or necrotising fasciitis
Encephalitis - good prognosis (unlike HSV) ataxic and cerebellum presentation
Purpura fulminans - consequence of vasculitis in skin and SC tissues, best known in relation to meningoccoal disease but can rarely occur after VZV infection
What can occur in immunocompromised patient with VZV
Primary infection can result in severe progressive disseminated disease - mortality of up to 20%
Vesicular eruptions persist and can become haemorrhagic
Treatment of chickenpox
Aciclovir has no proven benefit - unless immunocompromised
If organ dissemination has not occurred then vaciclovir can be used
Vaciclovir can be used in older children and adults who have worse illness
Prevention of chickenpox
Human varicella zoster immunoglobulin for immunocompromised patients following contact with chickenpox
Shingles in children?
Is uncommon
Occurs most commonly in thoracic regions and in children who had primary infection in first year of life
Shingles in immunocompromised infant
Can get recurrent or multi dermal shingles
Reactivated infection can also disseminate to cause severe disease
Features of EBV infection
Fever, malaise, tonsillopharyngitis, lymphadenopathy
Less commonly - Petechiae on soft palate, HSMG, maculopapualar rash, jaundice
Treatment of EBV
Symptomatic
If group a strep is grown on Tonsils (5%) can be treated with penicillin
How is CMV transmitted
Saliva, genital secretions or breast milk
Also more rarely blood products, organ transplant and transplacentally
What does CMV infection cause in normal hosts
Mild or sub clinical infection
May cause glandular fever type syndrome
What can CMV infection cause in immunocompromised host
Retinitis, pneumonitis, bone marrow failure, encephalitis, hepatitis, colitis and oesophagitis
When is CMV an important pathogen - eg. When high risk?
Following organ transplantation
How can CMV disease be treated - problem?
Ganciclovir or foscamet can be used but both have serious side effects
What does parvovirus B19 cause?
Erythema infectiosum or slapped cheek syndrome
When do parvovirus B19 infections typically occur
Outbreaks most common in spring but can happen at any time
What does parvovirus b19 infect
Erythroblastoid red cell precursors in bone marrow
What are the four clinical syndromes that parvovirus B19 can cause?
Asymptomatic infection - common about 5-10% of preschool children
Erythema infectiosum
Aplastic crisis
Fetal disease
Features of erythema infectiosum
Most common illness from parvovirus b19 infection
Viraemic phase of fever, malaise, headache and myalgia
Week later slapped cheek rash on face
Progressing to maculopapular rash on trunk and limbs
What is aplastic crisis
In children with haemolytic anaemias and parvovirus b19
Fetal disease with parvovirus b19
Maternal transmission may lead to fetal hydrops and death due to severe anaemia
But majority of infected fetuses will recover
When do enteroviruses commonly occur?
Autumn and summer
What different infections can enteroviruses cause?
Hand foot and mouth disease
Herpangina (vesicular and ulcerated lesions on soft palate and uvula)
Pleurodynia (acute illness with fever, pleuritic chest pain and muscle tenderness)
Myocarditis and pericarditis
Features of measles
Prodromal phase fever, cough, runny nose, conjunctivitis, marked malaise
Then development of Kopliks spots (pathognomic - White spots on red buccal mucosa) and rash
Pathognomonic sign if measles
Kopliks spots
Features of rash in measles
Starts behind the ears and spreads downwards onto face and then rest of body
Discrete maculopapular to begin with and then becomes blotchy and confluent
Serious complications of measles x3
Pneumonia
Encephalitis 1-2weeks after illness onset
Subacute sclerosing panencephalitis - 7 years after measles, loss of neurological function progresses to dementia and death
Treatment of measles
Symptomatic
Isolate infected children in hospital
If immunocompromised - ribavirin
Features of mumps x4
Fever, malaise and parotitis
In up to 30% it is sub clinical
Parotitis typically 1 day after general signs
Parotitis in mumps?
May be unilateral initially but usually progresses to be bilateral
Children may complain of earache on eating and drinking
Test in mumps
Plasma amylase may be elevated in association with abdominal pain - pancreatitis
Consequences of mumps infection
Usually mild and self limiting infection
Sometimes unilateral transient hearing loss
Viral meningitis in 10% and encephalitis in 1 in 5000
Epididymo-orchiditis rarely and unilaterally
Importance of rubella
Congenital infection can cause severe damage to fetus but usually mild in childhood
What age typically is affected by Kawasaki disease?
Age 6 months to 4 years
What sort of disease is Kawasaki disease?
Systemic vasculitis
Features of Kawasaki disease
Prolonged fever >5 days Adenopathy Conjunctivitis Inflammation of BCG site High inflammatory markers Red, oedeamotous palms and soles of feet - can peel Rash scarlitiform Lips or buccal mucosa red and inflamed
Serious complications of Kawasaki disease
Coronary artery aneurysm - therefore aspirin at high dose during infection and then maintenance dose for 6 weeks until echo shows no aneurysm
May need long term warfarin if serious
Treatment of Kawasaki
IV immunoglobulin
Persistent inflammation or fever may require infliximab, steroids or ciclosporin
What does mantoux pick up
Current tb (infection or disease) or past BCG
Features of TB x5
Prolonged fever, malaise, anorexia, weight loss or focal signs of infection
Treatment of TB
Triple or quadruple therapy with rifampicin, isoniazid, pyrazinamide, ethambutol - recommened until sensitivity found
Then reduce to rifampicin and isoniazid after 2 months
Usually for 6 months if uncomplicated
Give pyridoxine weekly to prevent peripheral neuropathy of isoniazid
HIV signs in children with mild immunosuppression
Lymphadenopathy or parotitis
Moderate HIV immunosuppression
Recurrent bacterial infections, candidiasis, chronic diarrhoea, lymphocytic interstitial pneumonitis
Severe immunosuppression with full blown aids
Opportunistic infections such as PCP, severe failure to thrive or encephalopathy and malignancy
Rare in children
Type of rash in rheumatic fever
Erythema marginatum, pink rings on the torso
Main criteria of rheumatic fever x5
Erythema marginatum Sydenham's chorea Polyarthritis Carditis (endo-, myo- or peri-) Subcutaneous nodules
Features of hand foot and mouth disease
Initial prodrome lasting 1-2 days
Followed by oral ulceration
Soon followed by macules and papules on the hand and feet - more commonly on margins than on soles/palms
Management of hand foot and mouth
Self-limiting therefore just monitor and keep up hydration
Cause of hand foot and mouth
Coxsackie virus (A16 most commonly)
What causes scarlet fever
Strep pyogenes (group A strep)
When does scarlet fever usually occur (age and season)
age 4 average
Autumn and winter
highly contageous therefore occurs in outbreaks
Features of scarlet fever
Initial sore throat, high fever and general malaise
Followed 12-48hr by rash that starts on abdomen and then spreads
Also lymphadenopathy
Strawberry tongue
Flushed face and circumoral pallor
Features of scarlet fever rash
Red, extensive, punctate like sand paper
Rash especially florid in skin folds
Complications of scarlet fever
Rheumatic fever
Streptococcal glomerulonephritis
Management of scarlet fever
Antibiotics - Phenoxymethylpenicillin (penicillin V) or azithromycin if pen allergic
Features of tetanus infection
Suspect if tonic muscle stiffness and spasm (including lock jaw) develops several days after skin wound or burn
Management of tetanus infection
Treat with antitoxin, wound debridement and general support
Features of diptheria infection
Fatal infection spread by droplet or touching infected material - close contact etc Grey/white film over back of throat High temp Breathing difficulties Sore throat
Where else can diptheria infect
Myocardium, adrenals and nervous system
Features of roseola infantum
Exanthem subitum, also known as 6th disease - caused by herpes virus 6
typically affects children 6m-2y
Very high fever for a few days (febrile convulsions common)
then maculopapular rash
diarrhoea and cough common
