A ten year, multicentre study of coagulase negative staphylococcal infections in Australasian neonatal units

Abstract

Objective: To study late onset systemic infections with coagulase negative staphylococci.

Methods: Prospective longitudinal study of coagulase negative staphylococcal infection in 18 Australasian neonatal nurseries.

Results: From 1991 to 2000 inclusive, there were 1281 cases of coagulase negative staphylococcal (CoNS) sepsis, comprising 57.1% of all late onset infections. The male/female ratio was 1.27:1 (p < 0.05). The incidence of CoNS sepsis was 3.46 episodes per 1000 live births. Most infected babies (71%) were 24-29 weeks gestation at birth (mode 26 weeks). The first positive culture was day 7-14 in 49% of babies (mode 10 days). Five cases of meningitis were reported, an incidence of 0.4% of all CoNS infections. Twenty nine babies (2.3%) had concurrent necrotising enterocolitis and CoNS septicaemia. Four babies (0.3%) died from CoNS infection, but CoNS infection possibly contributed to the death of an additional 20 babies (1.6%). The mortality directly attributable to CoNS infection was significantly lower than that from late onset infections with Staphylococcus aureus (13.1%; relative risk (RR) = 36.1 (95% confidence interval (CI) 13.0 to 100.2) or with Gram negative bacilli (14.2%; RR = 45.5 (95% CI 16.8 to 123.3)).

Conclusions: CoNS are currently responsible for most late onset neonatal infections. Most infected babies are < 30 weeks gestation at birth, and usually present between 7 and 14 days of age. CoNS infections may be associated with necrotising enterocolitis, although causality is unproven. Neonatal CoNS infections are relatively benign: meningitis is rare and mortality low compared with infection from other organisms. Over-vigorous attempts to reduce the incidence of CoNS infections using prophylactic antibiotics are not advisable.

Figure 1

Gestational age of infected babies at birth. NB 81 babies born at > 37 weeks gestation are not included.

Figure 2

Day of first positive culture of coagulase negative staphylococci from blood or cerebrospinal fluid. NB 160 babies whose first positive culture was at > 30 days old are not included.