[Neonatal sepsis: epidemiologic indicators and relation to birth weight and length of hospitalization time]

All cases of neonatal septicemia among neonates admitted to the neonatal unit in the pediatric department (CHUS) in Santiago de Compostela between 1992 and 1995 were studied. Our aims were: 1) To assess the incidence and microbial epidemiology. 2) To study the incidence of coagulase-negative staphylococci (CONS) sepsis stratified according to birth weight and gestational age. 3) To assess the incidence density of sepsis (IDS) and 4) To analyze the associated mortality.

One hundred eighteen episodes of sepsis in 103 neonates which fulfilled clinical and laboratory criteria with positive blood cultures were included in this study. Between the years of 1992 and 1995 there were 318 neonates suspect of having sepsis among the 2,083 who were admitted to the unit during this period and which came from our own maternity department, as well as other centers.

In this period there were 10,457 live births in our maternity department. The annual incidence of sepsis was 6/1000 live births. Early onset sepsis was observed in 2.5/1000 live births (26 cases) and the occurrence of late onset increased to 3.5/1000 live births (36 cases). Neonatal sepsis was confirmed in 103 neonates (4.9%) corresponding to 118 episodes of sepsis. S. epidermidis was the most frequent agent isolated in blood cultures (38.1%). The highest incidence of sepsis caused by S. epidermidis was observed in neonates below 1500 g (12.1%) and less than 32 weeks gestational age (13.4%). The incidence was lower in those whose birth weights were more than 2500 g (1.9%) and > 37 weeks of gestational age (1.6%), p < 0.001. Overall mortality due to sepsis was 0.7% and increased to 5.0% among hospitalized newborns with birth weights below 1500 g. The average IDS stratified in three groups of birth weight and gestational age was 18 sepsis work-ups per 1000 patient-days of hospitalization, the lowest IDS 12.9/1000 was found in neonates whose birth weights were between 1501 g and 2500 g in comparison with neonates who weighted more than 2500 g (21.5/1000), p < 0.05, and very similar to the IDS found in the intermediate group of gestational age (13.1/1000).

S. epidermidis and other CONS are the main agents causing sepsis in hospitalized neonates, although there is a decreasing trend of incidence (-71.1%) between the years 1992 and 1995 (5.0% vs 1.5%). Gram-negative organisms and S. agalactiae played a minor role as agents causing sepsis even though S. agalactiae is the most important agent in early onset sepsis. Overall mortality associated with sepsis (7/1000 live births) is in or under the average range of international statistics. Indexes of IDS are more valuable as epidemiological tools in assessing septicemia than the simple attack rate because they have taken into consideration the length of stay, number of hospitalized newborns, as well as the number of positive sepsis work-ups in the calculating process.