Microbes and the Inflammatory Response in Necrotising Enterocolitis

Necrotising enterocolitis (NEC) is a progressive disease of the neonatal intestine beginning in the distal ileum and proximal colon and characterised by inflammatory necrosis [1,2]. It typically affects low birth-weight, preterm infants who account for the majority (70–90%) of cases [3–5]. Since the 1960s, advances in medical care have raised the survival rate for preterm infants with increasingly shortened gestation periods, resulting in a concomitant surge in NEC cases. The overall incidence of NEC is generally accepted as ranging from <1% to 5% of neonatal intensive care unit (NICU) admissions, or up to 5 cases per 1,000 live births [4– 6]. There is an inverse relationship between NEC and birth-weight, so that very low birthweight infants (VLBW; <1500 g) carry the greatest burden of disease [4,5,7]. Caplan report‐ ed NEC rates for VLBW infants vary greatly across countries, ranging from 1.5% in Japan to 28% in Hong Kong, with racial disparity apparent in VLBW black infants who have an increased risk and greater associated mortality [5,8]. Despite advances in neonatal care, the overall mortality remains high at around 20–30% [3,8-10]. An estimated 20-40% of infants with NEC require surgery, which has a case fatality rate of up to 50%, the smallest, least mature infants having the worst prognosis [5]. Most cases of NEC are sporadic with no clear seasonal distribution, but outbreaks have been documented [5]. Treatment of NEC is mainly supportive with the administration of broad-spectrum antibiotics while surgery is indicat‐ ed for intestinal perforation or removal of necrotic bowel segments. NEC complications and sequelae include serious neurodevelopmental delay, poor growth, intestinal obstruction due to scarring, short bowel syndrome, and liver failure due to prolonged hyperalimentation [6, 9]. The annual financial cost of NEC is considerable and in the USA has been estimated at $500 million to $1 billion [9].