Neonatal sepsis (early and late onset)

The classification, and why it carries the rest

Neonatal infection is classified by the hour of onset, and the cut is 48 h:

• Early onset infection: less than 48 h
• Late onset infection: more than 48 h

That one line decides the rest. Early and late onset differ in where the infection comes from, in which organisms are found, and in which antibiotic is started, so the hour of onset is asked first and the rest follows from it.

Early onset: the source and the risk

The source in early onset infection is an ascending infection from the vaginal canal. The steps given are: a long period of membrane rupture, more than 18 h, then the organism invades the amniotic fluid, which is in direct contact with the fetal lung, and this process will end up with lung infection and later neonatal sepsis.

The risk factors given for early onset infection are:

• Prolonged or premature rupture, more than 18 h
• Chorioamnionitis

Early onset: the organisms

The organisms causing early onset infection are given as group B streptococci, Listeria monocytogenes, and other Gram-positive organisms.

A second page puts it differently, and that is worth holding because it is what an item turns on: in the newborn period the two most common causes of neonatal sepsis are group B Streptococcus and Escherichia coli. On that page Listeria monocytogenes was once a more common cause but it is now uncommon, Streptococcus pneumoniae is an uncommon cause of sepsis in neonates, and Staphylococcus aureus and group A Streptococcus are not as common but should be considered in newborns with cellulitis.

So when the stem says in addition to group B Streptococcus, the other one asked for is Escherichia coli.