Introduction

Bacterial sepsis of the neonate is defined as systemic signs of infection with bacteremia, occurring in the first 30 days of life. Meningitis accompanies sepsis in approximately one-quarter of cases of neonatal disease, but the two processes share a common etiology and pathogenesis. This chapter will cover only bacterial sepsis of the term infant; meningitis is covered elsewhere. Prematurity and residence in an intensive care unit are independent risk factors for bacterial sepsis that differ from sepsis in the term infant. In addition, the emphasis of this chapter will be on early-onset neonatal disease, with less of a concentration on late-onset sepsis.

Epidemiology

Although the ability to diagnose bacterial sepsis has improved, septicemia remains a frequent cause of neonatal morbidity and mortality. The first records of positive blood cultures were reported from Yale in 1928. Since this time there has been a changing prevalence of prominent bacterial organisms that cause sepsis in the neonate, requiring an ever-vigilant approach to this disease, and it is likely that changes will continue to occur with the use of intrapartum antibiotics.

Two distinct patterns of neonatal sepsis have been described, differentiated by time of disease onset, predominant organism, and associated risk factors. Early-onset disease is defined as occurring ≤7 days postnatally with a strong association with obstetrical complications or risk factors. Therefore, disease is caused by microorganisms that colonize the maternal genital tract.