Microbiology of neonatal and childhood infections Flashcards
Define congenital infections
Babies are born with congenital infections–i.e. transmitted vertically from mother to baby
Infection can occur at any time during pregnancy–Between first trimester and birth
- if it happens in first trimester - could have more serious consequences.
- later infection less serious
What does screening target in pregnancy? What else could it look at?
•Current screening mother during pregnancy
–Hep B
–HIV
–Syphilis
•Currently NOT screened but possible
–CMV
–Toxoplasmosis
–Hep C
–Group B Streptococcus
–Rubella
How do congenital infections present?
- Varied presentations and non-specific signs
- Need to be considered in any sick neonate
What is the ‘TORCH’ screen?
•‘TORCH’ screen
–Toxoplasmosis
–Other – syphilis; HIV; hepatitis B/C
–Rubella
–Cytomegalovirus (CMV)
–Herpes simplex virus (HSV)
What are the common clinical features of congenital infections?
•Common clinical features
–Mild/no apparent maternal infection
–Wide range of severity in the baby
–Similar clinical presentation
–Serological diagnosis
–Long term sequelae if untreated
•Examples
–Low platelets, rash
–Cerebral abnormalities
–Hepatosplenomegaly/hepatitis/jaundice
Describe the life cycle of toxoplasmosis.
The only known definitive hosts for Toxoplasma gondii are members of family Felidae (domestic cats and their relatives). Unsporulated oocysts are shed in the cat’s feces (1) . Although oocysts are usually only shed for 1-2 weeks, large numbers may be shed. Oocysts take 1-5 days to sporulate in the environment and become infective. Intermediate hosts in nature (including birds and rodents) become infected after ingesting soil, water or plant material contaminated with oocysts (2) . Oocysts transform into tachyzoites shortly after ingestion. These tachyzoites localize in neural and muscle tissue and develop into tissue cyst bradyzoites (3) . Cats become infected after consuming intermediate hosts harboring tissue cysts . Cats may also become infected directly by ingestion of sporulated oocysts (4). Animals bred for human consumption and wild game may also become infected with tissue cysts after ingestion of sporulated oocysts in the environment (5) .
Humans can become infected by any of several routes:
•eating undercooked meat of animals harboring tissue cysts (6).•consuming food or water contaminated with cat feces or by contaminated environmental samples (such as fecal-contaminated soil or changing the litter box of a pet cat) (7) .•blood transfusion or organ transplantation (8) .•transplacentally from mother to fetus (9) .
In the human host, the parasites form tissue cysts, most commonly in skeletal muscle, myocardium, brain, and eyes; these cysts may remain throughout the life of the host. Diagnosis is usually achieved by serology, although tissue cysts may be observed in stained biopsy specimens (10) . Diagnosis of congenital infections can be achieved by detecting T. gondii DNA in amniotic fluid using molecular methods such as PCR (11)
What are the consequences of congenital toxoplasmosis?
•May be asymptomatic at birth
– 60% but may still go on to suffer long term sequelae
–Deafness, low IQ, microcephaly–
40% symptomatic at birth
–Choroidoretinitis
–Microcephaly/hydrocephalus
–Intracranial calcifications
–Seizures
–Hepatosplenomegaly/jaundice
What is the mechanism of congenital rubella syndrome infection? What are the consequences?
- Effect on foetus – dependent on time of infection
- Mechanism – mitotic arrest of cells; angiopathy; growth inhibitor effect•
Eyes: cataracts; microphthalmia; glaucoma; retinopathy
- Cardiovascular syndrome: PDA; ASD/VSD
- Ears: deafness
- Brain: microcephaly; meningoencephalitis; developmental delay
- Other: growth retardation; bone disease; hepatosplenomegaly; thrombocytopenia; rash
Describe the picture
Congenital rubella syndrome
Describe the image
HSV
What are the other congenital infections
What is the neonatal period
•Definition varies
–First 4-6 weeks of life–
•If born early (premature)
–Neonatal period longer and is adjusted for expected birth date
Why is infection relevant in neonatal period?
- Higher incidence of infections
- Can become ill rapidly and seriously
- Unlike adults or older children – need to treat with antibiotics when first suspicion of infection
- Immature host defences
- Increased risk with increased prematurity
–Less maternal IgG
–NICU care
–Exposure to microorganisms; colonisation and infection
How do we classify neonatal infections?
- Early and late onset infection
- Early onset – usually within 48 hours of birth
–Some definitions 3-5 days
•Organisms
–Group B streptococci
–E. coli
–Listeria monocytogenes
Describe group B streptococci
- Gram positive coccus
- Catalase negative
- Beta-haemolytic
- Lancefield Group B
- In neonates: Can go to the CNS, into the blood and then the CNS
–Bacteraemia
–Meningitis
–Disseminated infection e.g. joint infections
Describe E.coli
- Gram negative rod
- In neonates:
–Bacteraemia
–Meningitis
–UTI
What type of infection might this be?
Listeria monocytogenes - food hygiene!
Gram +ve rod
Classical appearance
What are early onset sepsis-risk factors
What are the investigations for early onset sepsis?
- Full blood count
- C-reactive protein (CRP)
- Blood culture
- Deep ear swab
- Lumbar puncture (CSF)
- Surface swabs
- Chest X-ray (full body)
How do we treat early onset sepsis?
•Supportive management:
–Ventilation
–Circulation
–Nutrition
–Antibiotics: e.g. benzylpenicillin & gentamicin
If meningitis, add amoxicillin
What is late onset sepsis? What microorganisms cause it?
How do we treat late onset sepsis?
What is the clinical significance of meningitis in childhood?
It can be difficult to do an LP (low plus) - look for strep and pneumococcus in blood
Complete the table
- If no growth PCR may be positive
- Rapid antigen tests can be useful
Gram -ve coccus - neisseria meningitides
What is this?
Non-blanching rash. Bacterial meningitis
What is this?
Meningococcal rash
What is this?
Severe meningococcal rash
What is this?
Streptococcus pneumonias - gram +ve - pneumococcus
Gram -ve rod, haemophilia influenza. Rarely causes meningitis. High morbidity.
Plate - needs to be burned blood (red cell lysed)
What are the common organisms causing meningitis in different age groups?
What are the common causative organisms that cause RTIs in childhood?
Describe mycoplasma pneumonias. How does it present? Who does it affect?
What are the extra-pulmonary manifestations of mycoplasma pneumonia?
If persistent cough, what should we consider?
Describe UTIs in childhood.
How should UTIs be managed in A&E?
What is this?
E. coli
What are the other organisms causing UTIs?
How should we manage UTIs?
Recurrent or persistent infections
- May be a sign of immunodeficiency – either congenital or acquired – e.g. HIV, SCID•
- Warrants investigation by Paediatric Infectious Diseases doctors
Group B strep
Men B
