Characteristics of Invasive Staphylococcus aureus in United Kingdom Neonatal Units

Background: In industrialized countries, Staphylococcus aureus (SA) is a leading cause of late-onset neonatal sepsis. Methods: Culture-proven episodes were identified prospectively from neonatal units participating in the neonatal infection surveillance network. Demographic, risk factor, and outcome data were collected. Results: Between 2004 and 2009, there were 117 episodes of SA infections (including 8 methicillin-resistant SA) in 116 infants from 13 units. The median gestational age and birth-weight were 27 weeks (90% <= 37 weeks, 85% <= 32 weeks) and 850 g (90% <= 2500 g), respectively. The overall incidence was 0.6 per 1000 live births and 23/1000 in infants < 1500 g. Most episodes (94%) occurred more than 48 hours after birth (late onset). There were 7 early-onset episodes (< 48 hours) (median gestational age, 38.5 weeks), all due to methicillin-susceptible SA. At the time of culture, 67 of 95 (71%) infants were receiving respiratory support and 47 of 94 (50%) had a central line in situ. The majority of infants had nonspecific clinical features although evidence of focal infection (skin, soft tissue, bone, joint, or pneumonia) was ultimately seen in 41 of 91 (45%). There were 18 deaths, 4 (all late onset) directly due to methicillin-susceptible SA sepsis (4.4%). Conclusions: SA is the second most common pathogen causing late-onset neonatal infections in this neonatal network. Infants who weigh < 1500 g in intensive care settings are the most vulnerable group. Clinical signs are not sufficiently distinctive to allow targeted therapy, suggesting that an antistaphylococcal agent should be part of empiric therapy for late-onset sepsis in premature infants.