pediatrics
Neonatal Sepsis
Pathophysiology of Neonatal Sepsis
Certain maternal perinatal and obstetric factors increase risk, particularly of early-onset neonatal sepsis, such as the following: Prelabor Rupture of Membranes (PROM) (PROM) occurring Maternal Intraamniotic Infection (most commonly manifesting as maternal fever shortly before or during delivery with maternal leukocytosis, tachycardia, uterine tenderness, and/or foul-smelling amniotic fluid) Colonization with GBS Preterm Labor None Hematogenous and transplacental dissemination of maternal infection occurs in the transmission of certain viral (eg, Congenital Rubella , Though the intensity of maternal colonization is directly related to risk of invasive disease in the neonate, many mothers with low-density colonization give birth to infants with high-density colonization who are therefore at risk. Amniotic fluid contaminated with meconium or vernix caseosa promotes growth of group B streptococcus andE. coli. Hence, the few organisms in the vaginal vault are able to proliferate rapidly after PROM, possibly contributing to this paradox. Organisms usually reach the bloodstream by fetal aspiration or swallowing of contaminated amniotic fluid, leading to bacteremia. The ascending route of infection helps to explain such phenomena as the high incidence of PROM in neonatal infections, the significance of adnexal inflammation (amnionitis is more commonly associated with neonatal sepsis than is central placentitis), the increased risk of infection in the twin closer to the birth canal, and the bacteriologic characteristics of early-onset neonatal sepsis, which reflect the flora of the maternal vaginal vault. Themost important risk factorin late-onset sepsis is Preterm Labor None Other risk factors include Prolonged use of intravascular catheters Associated illnesses (which may, however, be only a marker for the use of invasive procedures) Exposure to antibiotics (which selects resistant bacterial strains) Prolonged hospitalization Contaminated equipment or IV or enteral solutions Gram-positive organisms (eg, coagulase-negative staphylococci andStaphylococcus aureus) may be introduced from the environment or the patient’s skin. Gram-negative enteric bacteria are usually derived from the patient’s endogenous flora, which may have been altered by antecedent antibiotic therapy or populated by resistant organisms transferred from the hands of personnel (the major means of spread) or contaminated equipment. Therefore, situations that increase exposure to these bacteria (eg, crowding, inadequate nurse staffing, inconsistent provider handwashing) result in higher rates of hospital-acquired infection. Risk factors for candidal sepsis include prolonged (>10 days) use of central IV catheters, hyperalimentation, use of antecedent antibiotics (especially 3rd-generation cephalosporins), and abdominal pathology. Initial foci of infection can be in the urinary tract, paranasal sinuses, middle ear, lungs, or gastrointestinal tract and may later disseminate to meninges, kidneys, bones, joints, peritoneum, and skin. 