Neonatal sepsis occurs when a serious bacterial or viral infection in the blood affects babies within the first 28 days of life. Neonatal sepsis is categorised into:

• early-onset (<72 hours of life)
• late-onset (>72 hours)

with each category tending to have a distinct group of causes and common presentations.

Neonatal sepsis account for 10% of all neonatal mortality and therefore must be promptly identified and managed to prevent significant consequences, as untreated, the mortality can be very high.

Epidemiology

• Male:female incidence 1:1
• Incidence of neonatal sepsis: 1-5 per 1000 live births
  • Term neonates: 1-2 per 1000 live births
  • Late pre-term infants: 5 per 1000 live births
  • Birth weight <2.5kg: 0.5 per 1000 live births
• Black race is an independent risk factor for group B streptococcus-related sepsis

Causes

• Neonatal infection is present in 8 per 1000 live births (note: this is the incidence of neonatal infection, not yet necessarily progressed to neonatal sepsis), and is the key factor which leads to subsequent life-threatening neonatal sepsis

Causative organism: The overall most common causes of neonatal sepsis are group B streptococcus (GBS)/Streptococcus agalcticae and Escherichia coli, accounting for approximately two thirds of neonatal sepsis cases

• Early-onset sepsis in the UK is primarily caused by GBS infection (75%)
  • Infective causes in early-onset sepsis are usually due to transmission of pathogens from the mother to the neonate during delivery
• Late-onset sepsis usually occurs via the transmission of pathogens from the environment post-delivery, this is normally from contacts such as the parents or healthcare workers
  • Infective causes are more commonly coagulase-negative staphylococcal species such as Staphylococcus epidermidis, Gram-negative bacteria such as Pseudomonas aeruginosa, Klebsiella and Enterobacter, and fungal species
• Other less common causes include:
  • Staphylococcus aureus
  • Enterococcus
  • Listeria monocytogenes
  • Viruses including herpes simplex and enterovirus

Risk factors

• Mother who has had a previous baby with GBS infection, who has current GBS colonisation from prenatal screening, current bacteruria, intrapartum temperature ≥38ºC, membrane rupture ≥18 hours, or current infection throughout pregnancy
• Premature (<37 weeks): approximately 85% of neonatal sepsis cases are in premature neonates