Late onset neonatal Gram-negative bacillary infection in Australia and New Zealand: 1992-2002

Abstract

Background: Late onset neonatal Gram-negative bacillary infection is a significant cause of morbidity and mortality.

Objective: To determine the incidence and mortality from late onset Gram-negative bacillary infections in neonatal units.

Methods: An 11-year longitudinal prospective surveillance study. Clinicians in 20 neonatal units in Australia and New Zealand collected data. Late onset sepsis was defined as clinical signs of infection starting more than 48 hours after birth, with laboratory evidence supporting sepsis and pure growth of a pathogen from blood and/or cerebrospinal fluid.

Results: Overall, 702 of 3113 (22.5%) episodes of late onset sepsis in 681 infants were from Gram-negative bacilli. Overall mortality was 20.8% (142 of 681 infants) and significantly related to maturity, birth weight and infecting organism. Mortality was 25% for infants <30 weeks compared with 11.5% for infants > or =30 weeks gestation (P < 0.0001) and 24.2% for infants with birth weights <1500 g versus 12.7% if > or =1500 g (P < 0.0001). Infection by Pseudomonas aeruginosa was associated with 52.3% mortality (46 of 88 infants), significantly higher than the 13.7% to 23.8% fatality from other Gram-negative bacilli (P < 0.0001). During the surveillance, the late onset Gram-negative bacillary infection rate remained stable at 1.14 per 1000 live births (range 0.87-1.5). Similarly, mortality was unchanged, being 0.25 per 1000 live births (range 0.12-0.43).

Conclusions: Gram-negative bacilli remain important causes of late onset neonatal sepsis, especially among very low birth weight infants, and result in a high mortality, particularly with P. aeruginosa infections.