Infectious diseases Flashcards
Conditions caused by GAS (strep pyogenes)
Pharyngitis
Retropharyngeal abscess
Scarlet fever
Impetigo, erysipelas, cellulitis (inc perianal)
Strep TSS
Rheumatic fever
APSG
Describe scarlet fever rash
- Fine, diffuse “sandpaper” rash - appears 24-48 hrs into illness (after 1st fever) but can be first sign
- Begins on neck and upper chest, spreads to rest of trunk and extremities, spares palms and soles
- Prominent in flexor skin creases (Pastia lines [from capillary rupture] - pathognomonic for scarlet fever)
- Lasts approx 1 week then fades with desquamation of trunk, hands and feet
Features of scarlet fever
- Due to GAS pyrogenic exotoxin
- Pharyngitis, lymphadenopathy, fever
- Sandpaper rash, appears 1-2 days post onset of fever
- Pastia’s lines
- Strawberry tongue
- Circumoral pallor
- Desquamation of trunk, hands and feet with fading of rash (~1 week after onset)
- Abdo pain, myalgia, malaise
What systemic complication is associated with impetigo? (GAS)
Post strep GN (from M serotypes 49, 55, 57,59)
NOT rheumatic fever
CMV (HHV-5) transmission
Urine, resp secretions, blood
Vertically - in utero by transplacental passage, passage through infected genital tract, postnatally via breast milk (or donor milk)
CMV cytomegalic inclusion disease signs
IUGR
Jaundice, hepatosplenomegaly
Thrombocytopaenia/anaemia
Blueberry muffin rash (also in rubella)
Microcephaly, cerebral atrophy
Chorioretinitis
SNHL
Lethargy, hypotonia, seizures
Periventricular intracebral calcifications (CMV CircuMVents the ventricles)
CMV - SNHL stats
10% asymptomatic children (1/3 if symptomatic) will have progressive SNHL +/- neurodisability (also seizures and CP)
Eye signs CMV v rubella
CMV - chorioretinitis
Rubella - cataracts
Risk period of CMV infection in pregnancy
Early in pregnancy - transmission rate 30-50%
Diagnosis CMV
Urine CMV culture/PCR (and other sites) - must be within 2-4 wks to be “congenital”
Infant blood for CMV PCR
Paired maternal and infant serology
+ neuroimaging, opthal, audiology
MRI findings of CMV
Ventriculomegaly (hydrocephalus)
Periventricular calcifications
CMV v toxoplamosis MRI
CMV - microcephaly, ventriculomegaly, periventricular calcifications, lenticulostriate changes
Toxoplasmosis - hyrocephalus, diffuse cerebral calcifications
Congenital CMV treatment
Oral valganciclovir if <28 days AND moderate symptomatic disease (or IV ganciclovir if poor oral absorption)
Must treat for 6 mths
Risk of neutropaenia
TORCH
Toxoplasmosis
Other - syphilis, VSV, parvovirus, enteroviruses, Zika, GBS
Rubella
CMV
HSV
Neonatal HSV - risk of transmission
High if primary infection og genital herpes near the time of delivery
Low if hx of recurrent herpes
60-80% of pregnant F with HSV + babies have no prior clinical hx of HSV sx
Neonatal HSV presentation
45% - skin, eyes, mouth (SEM) - present in 1st 1-2 wks (sx = vesicular lesions, conjunctivitis, keratitis, chorioretinitis)
30% CNS only - present in 2nd-3rd week (sx = irritability, sz, poor feeding, lethargy - haemorrhagic CSF common with HSV)
25% disseminated - present in 1st 1-2 wks (sx = liver, lung, heart, kidney, CNS). Fatal in 50% cases
Neonatal HSV workup
HSV culture of mth, nasopharynx, eyes, anus
HSV culture and PCR of skin and mucosal lesions
HSV PCR of blood and CSF
LFTs
CXR
Opthal
Neuroimaging - MRI
Neonatal HSV treatment
Skin, eyes, mouth (SEM) - IV acyclovir 14 days
CNS or disseminated - IV acyclovir min 21 days + 6 mths PO acyclovir suppressive therapy
Hep B - chronic infection and complications rate of perinatal infections
90% become chronically infected if contract perinatally
25% develop cirrhosis and/or liver cancer in adult life
Maternal hep B Ag status - risk of transmission
Hep B - prevention of maternal transmission
1) Universal screening - if high initial, test viral load
2) Infants born to HbsAg pos Mo -> Hep B vaccin and HBIG within 12 hrs of birth
3) 3 further doses of Hep B vaccine as per immunisation schedule
4) Infant testing at > 9 mths to monitor surface antibody and rule out infection (ie HBsAg neg)
5) +/- tenofovir anti-viral Rx in Mo
Parvovirus B19 - complication of neonatal infection
Fetal anaemia, cardiac failure, hydrops
Treatment for parvovirus B19
No intervention available to prevent infection
Test fetus -> if positive, intrauterine transfusion to prevent foetal anaemia/hydrops
Monitor for anaemia postnatally
Presentation of neonatal parechovirus
Sepsis features - high fever, tachycardia, irritability, mottling, poor perfusion
Other - mottled red rash (erythrodermic), abdo distension, oedema, hepatitis
Presentation more severe than appears from bloods
Test via PCR (throat/rectal swabs)
Nb HPeVs-3 outbreak 2015
Condition?
Parechovirus - septic, oedematous, mottled red rash, abdominal distension
Congenital rubella - antenatal risk period
Highest risk if maternal infection pre-conception or 1st trimester (up to 50%)
Congenital rubella syndrome - classic triad
SNHL (58%)
Eyes - cataracts, retinopathy, micropthalmia (43%)
Cardiac - PA stenosis, PDA
Antenatal risk of VSV
Highest between 8 and 20 wks gestation - more likely to have birth defects then
VSV - clinical signs
Cicatricial skin scarring (dermatomal distribution)
Limb hypoplasia
Microcephaly, cortical atrophy
Seizures
Cataracts
Chorioretinitis, micropthalmia, nystagmus
Neuro defects
VSV treatment for exposed pregnant women
If immune compromised -> give VZ IG ASAP - until 10 days post exposure
If not available - give IVIG
Do NOT give VSV vaccine if pregnant (live vaccine)
Treatment for neonatal exposure to maternal VSV
> 7 days before delivery - no treatment
<7 days before ->2 days post - give VZIG
If under 28 weeks - give VZIG (maternal antibodies would not have crossed placenta)
Toxoplasmosis - how caught + presentation
Risk factors - ats, kitty litter, gardening, eating unwashed/raw vegetables or undercooked meat
Self limited non-specific illness in immune competent hosts
Crosses placenta 4-8 wks after maternal infection
Toxoplasmosis - risk of maternal infection
1st trimester - low risk (10-15%) but complications +++
1nd trimester - 30%
3rd trimester - 60%, but low complication rate
Congenital toxoplasmosis - clinical features
85% normal at birth
Of these, 85% if untreated will have 1 or more episodes of chorio-retinitis
Hearing loss 10-30%, developmental delay 20-75%
Only 75% of congenitally infected produce detectable IgM
Toxoplasmosis - antenatal diagnosis
Maternal IgM detectable within 1-2 wks, undetectable by 6-9 mths
IgG avidity (bonding of antigen and antibodies)
Fetal antibody - unlikely before 20 weeks
Amniotic fluic PCR - good after 18 weeks gestation
Toxoplasmosis - antenatal treatment
If maternal infection but fetus not affected - Spiramycin
If Mo and fetus infected - Pyrimethamine plus Suphadiazine
Neonatal diagnosis of toxoplasmosis (if sx)
Paired maternal and infant serology (IgM, IgG, IgG avidity)
PCR on blood +/- CSF
CSR, neuro imaging, opthal, audiology
Monitor IgG and IgM over time
Condition?
Toxoplasmosis
Toxoplasmosis - treatment in infant
Treat until 12 mths
- Pyrimethamine (haem toxicity - monitor)
- Sufadiazine
- Folinic acid (leucovorin)
Monitor FBC due to risk of neutropaenia
Neurodevelopmental, opthal, audiology f/u
GBS - presentation
Early onset <5-7 days - sepsis, pneumonia, meningitis 10%
Late onset >5-7 days - occult bacteraemia, meningitis 30%, osteoarticular involvement
Very late onset >90 days - usually in premature or prolonged hospital stay
Neonatal syphillis - signs
Osteochondritis/periostits
Snuffles, haemorrhagic rhinitis
Skin - bullous lesions, palms/soles involved (desquamating rash), mucous patches
Unexplained large placenta
Nephrotic syndrome (rare - usually 2-3 mths old)
Hepato/splenomegaly, jaundice
Non-immune hydrops fetalis
Infant syphilis workup
Serology - trepenemal (TPPA aka acquired antibodies from Mo) + RPR - level of disease response
Long bone xrays - periosteal reactions
LP - SCF VDRL, protein, cell count
Skin lesions/placenta - darkfield microscopy for spirochetes
Check if Mum had full STI evaluation (HIV, hep B&C)
Treatment if confirmed/suspected - 10 days IV benpen
F/U infant serology 3&6 mths
Condition?
Herpetic whitlow
May treat with acyclovir
Do NOT burst lesions
HHV-6 - symptoms
Roseola (6th disease, exanthema subitum)
Fever 3-5 days, then abrupt cessation of fever
Then macular-to-maculopapular rash
Seizures can occur in febrile stage
Other: Nagayama spots, irritability, LOA, diarrhoea, URTI sx, lymphadenopathy, palpebral/periorbital oedema (Berlinger sign)
Quantitiative HIV RNA viral load reverse transcriptase (RT) CPR
1st line to diagnose infectivity. In adults and older kids, ELISA and Western blotting can be used to detect HIV specific antibodies.
Can be performed within 24 hrs of infection.
A positive virologic result should be confirmed with repeat testing with a 2nd sample ASAP after result is available.
UTI bugs
F: E Coli, Klebsiella, Proteus
M: E Coli, gram + organisms
UTI treatment in infant
Neonate - amox + gent
Infant - ceftriaxone
Duration IV treatment meningitis > 1mth
N meningitidis - 5 days
S pneumoniae - 10-14 days
H influenzae - 7 days
GBS - 14-21 days
Gram neg bacilli - 21 days
Listeria - 21 days
Cerebellar ataxia + oculucutaneous telangectasia - ?dx
Ataxia telangiectasia
- Ataxia usually presents before age 5 yrs
- Telangiectasia most common in bulbar conjunctivae, but also ears, neck and ACF
- AFP is raised
Pin worm/threadworm
Enterobius vermicularis
- Eggs = bean shaped
- Adult females = pin shaped.
- Presents as white threads in stool
Whipworm
Trichuris
- Occurs in tropics
- Ass. with poor hygiene & poverty
- Usually asymptomatic, but can have symptoms if heavy parasite burden
- Eggs = barrel shaped
- Complications = rectal prolapse
Hookworm
Necator americanus
- Chronic infection leads to anaemia and poor gth
- Often ass. with eosinophilia
Necator americanus - regions
Hookworm
Africa, Americas, Indonesia, Sth Pacific
Necator duodenale - regions
Hookworm
Mediterranean countries, Iran, India, Pakistan, Far East
Hookworm varieties
Necator americanus
Ancylostoma duodenale
Ancylostoma braziliense (cats and dogs)
Ancylostoma caninum (dogs)
Roundworm varieties
Ascaris lumbrocoides (humans)
Ascaris suum (pigs)
Trichuris (whipworm)
Pinworm/threadworm
Enterobius vermicularis
Hep C - method of transmission
IV blood exposure
Mucous membranes possible but less efficient
Abx treatment CAP > 2 mths
High dose amoxicillin - studies have shown equivalent outcomes to parenteral therapy for moderately severe CAP
Dengue
Flavivirus
- Aedes aegypti mosquito
- Sx: high temp, myalgias, retro-orbital headache
- Also: thrombocytopaenia and mild bleeding (petechiae, epistaxis) at defervescence common
- Dengue haemorrhagic fever can lead to distributive shock
- Similar to Chikungunya, but C does not have bleeding sx
Plasmodium vivax
- Malarial illness
- Mild cf P faciparum
- May occur despite prophylaxis
- Dormant hepatic phase, so may present some mths/years after initial infection
- Ix = thick and thin blood films, but PCR and antigen testing is possible
Enterotoxigenic e coli
- Most common form of traveller’s diarrhoea
- Sx = watery diarrhoea and abdominal cramping +/- vomiting +/- fever
- If high fever or bloody diarrhoea, think campylobacter jejuni or S typi
CXR - myocarditis
Enlarged cardiac shadow
Bilateral patchy opacification (from HF/viral infection)
Pathogenic mosquitos
- Aedes aegyptes - Dengue fever and Zika
- Anopheles - malaria
- Tsetse flies - trypanosomiasis
- Sandflies - leishmaniasis
- Ixodes ticks - Lyme disease
Endocarditis prophylaxis - when indicated
- Prosthetic cardiac valve
- Previous IE
- CHD if unrepaired cyanotic defect (or persistent defect post repair), for 6 mths post op
- heart transplant with valvulopathy
- RHD if extraction, periodontal, replanting avulsed teeth, other surgery
Commonly associated bacteraemia in malaria
Salmonella
Thick and thin blood smear - used to detect what?
Malaria
- Thin - measures parasite density AND identification of parasite (through RBC morphology)
- Thick - parasite density. RBC lysed so does NOT identify particular parasite.
Indications for IvIG
- Dermatomyositis (reduces MAC in plasma, and C3b and MAC deposited in endomysial capillaries)
- Guillain-Barre syndrome (hastens recovery)
- ITP (superior to corticosteroids)
- Kawasaki’s (used with aspirin reduces risk of CA aneurysms)
Otitis externa - bugs
P aeruginosa
S epidermidis
S aureus
Diagnosis?
Varicella zoster virus
Would be itchy but NOT painful (cf otitis externa)
Enterococcus fecalis
- Gram positive cocci
- Causes UTIs in pts with indwelling catethers or underlying renal tract abnormalities
- Cephalosporin resistant
Bacterial tracheitis - bug
- Staph aureus - most common
- Moraxella catarrhalis - more severe disease
- Strep pneumoniae
Viral causes of paralysis
Poliovirus type 3
Enterovirus 71
HHV-6
- aka roseola infantum, exanthem subitum, 6th disease
- 3-5 days fever, resolves abruptly following by rash
- acute febrile illness with or without rash with fever, fussiness, rhinorrhoea
IV agent for neonatal candiasis
Amphoterocin B
Features of GAS perianal infection
Perianal erythema
Fever
Intensely itchy
Pain on defection
Mucopurulent anal discharge
PFAPA (Marshal syndrome) - acronym
Periodic fever with aphthous stomatitis, pharyngitis and adenitis
NOT associated with amyloidosis
Periodic fever syndrome associated with amyloidosis
Familial mediterranean fever
Granulomatosis infantiseptica
- Caused by listeria when severe in utero infection
- Causes abscesses in fetal liver, lungs, kidney, spleen and brain
- Stillborn or die shortly after birth
Meningococcal serotypes
A - linked with outbreaks in Africa and Asia
B - most common
C - 2nd most common
W135 - responsible for small outbreaks internationally, increasingly common in Aust
Y - uncommon in Austraia
HFM virus
Coxsackie A16
ESKAPE organisms (multi-drug resistant organisms)
Enterococcus faecium
Staphylococcus aureus Klebsiella pneumoniae Acinetobacter baumannii Pseudomonas aeruginosa Enterobacter spp.
Leishmania - method of transmission
Sandflies
