Obstetric and Perinatal Infections

Question 1

Why is the newborn immune system especially susceptible?

Answer 1

1. Cells have a high growth rate
2. Maternal immunosuppression
3. Fetal immune system is immature (all immunity is passive via maternal transplacental IgG and IgA in breast milk)

Question 2

What are the three routes of infection for obstetric / perinatal infection?

Answer 2

1. Congenital - across placenta in utero
2. Perinatal - acquisition during birth canal passage (in utero)
3. Postnatal - milk, blood, saliva, contact

Question 3

What is the leading cause of bacterial meningitis in newborns?

Answer 3

Group B Streptococci - Strepococcus agalactiae

Question 4

What is the morphology of Group B Strep (GBS) and where does it normally live? How does the baby get it?

Answer 4

Gram positive diplococci

Normally lives in GI and GU tract of mom

Baby gets it from having a large inoculum inhaled or eaten during birth (oropharyx, gastrointestinal tract)

Question 5

What are the risk factors for early onset GBS?

Answer 5

Heavily colonized mother lacking specific anti-capsule antibody, with pre-term delivery, preterm rupture of membranes, and prolonged labor

Question 6

What results from early onset GBS?

Answer 6

Meningitis, pneumonia, and bacteremia within 7 days of both, which is 60% fatal with sequelae in survivors

Question 7

What is used for prevention of early onset GBS?

Answer 7

“Blind” treatment of sick baby who has risk factors

Question 8

What is late onset GBS and is it better or worse in prognosis?

Answer 8

GBS at 7 weeks to 3 months, better prognosis as horizontal and nosocomial transmission may be implicated. Only 20% fatal, with predominantly meningitis

Question 9

What is the primary virulence factor of GBS and how does it work?

Answer 9

Polysaccharide capsule with sialic acid moiety on terminal sugar, limiting C3b deposition and decreasing phagocytosis

Question 10

What is the primary GBS virulence factor related to pneumonia? How does it play into meningitis?

Answer 10

Beta-hemolysin causes lung epithelial cell injury, can also help with invasion through blood brain barrier

Question 11

What is intrapartum prophylaxis for GBS?

Answer 11

Use of antibiotics to reduce GBS load (as part of normal flora) in mom to prevent risk of infection

Question 12

What is the second leading causing of neonatal meningitis? What is its morphology?

Answer 12

Escherichia coli K1

Gram negative bacillus

Question 13

What is the prognosis for E. coli meningitis and how is it contracted?

Answer 13

Via ruptured amniotic membranes in low BW and pre-term births

Prognosis is poor, mortality as high as 80% with survivors having CNS sequelae.

Most will present with septicemia

Question 14

What are the two primary virulence factors of E. coli K1?

Answer 14

1. Polysialic capsule - resistance to neutrophil killing and survival in blood and CSF
2. Invasins - Contribute to crossing of blood-brain-barrier

Question 15

What is the morphology of Listeria monocytogenes?

Answer 15

Gram positive rod

Question 16

What is the immunity against L. monocytogenes and who is most at risk?

Answer 16

Immunity is primarily cell-mediated

At risk: immunosuppressed and pregnant women / neonates

Question 17

What are the routes of infection of newborns for Listeria? Most common way?

Answer 17

congenital (transplacental), perinatal (ascending) or postnatal

Most commonly: mother contracts via food-borne transmission, transfers to fetus

Question 18

What are the in utero results of Listeria infection?

Answer 18

Spontaneous abortion, premature birth, stillbirth, or death within a short period after birth. Infant will have septicemia develop within hours of a perinatal infection

Question 19

What will Listeria most likely cause if contracted perinatally?

Answer 19

Meningitis (3rd leading cause in newborns, beside GBS and E. coli K1)

Question 20

What three virulence factors mediate the lifestyle of Listeria and how?

Answer 20

Intracellular lifestyle

1. Internalins - adhesins aiding in cell invasion
2. Listeriolysin O - helps Listeria escape from host vacuoles
3. ActA - recruits host actin filaments to spread to neighboring cell without leaving previous cell (evade humoral immune response)

Question 21

What is one atypical way humans can become infected with T. gondii?

Answer 21

Blood transfusion / organ transplantation (if organ contains bradyzoites)

Question 22

When does congenital T. gondii infection affect the baby and when is it worst?

Answer 22

Affects the baby when its the mother’s first time being exposed (no immune response)

Worst when the fetal infection happens earlier in pregnancy

Question 23

What do infants born with T. gondii often show? (if not aborted or stillbirthed)

Answer 23

Microcephaly, hydrocephaly, psychomotor disturbances, and convulsions (CNS involvement)

Question 24

What is the most common complication of T. gondii infection?

Answer 24

Chorioretinitis, with bouts of eye pain and loss of visual acuity

Question 25

What are longterm sequelae of neonatal T. gondii infection?

Answer 25

Epilepsy or cognitive impairment years later

Question 26

How is T. gondii detected in utero?

Answer 26

Via PCR of amniotic fluid