246 SECTION II Bacterial Infections inadequ<strong>at</strong>e nutrition, lack of pren<strong>at</strong>al care, and infectious medical complic<strong>at</strong>ions encountered in addicted pregnant women [415,416]. ADMINISTRATION OF DRUGS OTHER THAN ANTIBIOTICS TO THE NEONATE Administr<strong>at</strong>ion of indomethacin to neon<strong>at</strong>es for the closure of a p<strong>at</strong>ent ductus arteriosus has been associ<strong>at</strong>ed with a higher incidence of sepsis and necrotizing enterocolitis in the indomethacin-tre<strong>at</strong>ed groups compared with infants tre<strong>at</strong>ed with surgery or other medic<strong>at</strong>ions [417–419]. The mechanism by which indomethacin predisposes low birth weight infants to sepsis is unknown [420]. A meta-analysis of studies comparing ibuprofen with indomethacin for p<strong>at</strong>ent ductus arteriosus closure did not identify differences in the incidence of sepsis, mortality, or dur<strong>at</strong>ion of hospitaliz<strong>at</strong>ion [421]. O’Shea and colleagues [420] described the outcomes of very low birth weight (500 to 1250 g) infants given dexamethasone <strong>at</strong> 15 to 25 days of age for the prevention of chronic lung disease. Among 61 infants tre<strong>at</strong>ed with tapering doses of dexamethasone for 42 days, there was no increase in the incidence of sepsis or the number of sepsis evalu<strong>at</strong>ions in the tre<strong>at</strong>ment group compared with a control popul<strong>at</strong>ion. Further trials of dexamethasone administr<strong>at</strong>ion for prophylaxis of chronic lung disease in very low birth weight infants confirmed a lack of increased risk for sepsis [422]. A strong associ<strong>at</strong>ion between intravenous lipid administr<strong>at</strong>ion to newborns and bacteremia caused by CoNS has been established [99,423]. The role of lipid as a nutritional source for the bacteria, mechanical blockage of the c<strong>at</strong>heter by deposition of lipid in the lumen, and the effect of lipid emulsions on the function of neutrophils and macrophages each might contribute to the observed increased risk for bacteremia. Avila-Figueroa and colleagues [423] identified exposure to intravenous lipids <strong>at</strong> anytime during hospitaliz<strong>at</strong>ion as the most important risk factor (odds r<strong>at</strong>io 9.4) for development of CoNS bacteremia in very low birth weight infants, calcul<strong>at</strong>ing th<strong>at</strong> 85% of these bacteremias were <strong>at</strong>tributable to lipid therapy. A randomized trial found th<strong>at</strong> changing intravenous tubing for lipid infusion in neon<strong>at</strong>es every 24 hours instead of every 72 hours may reduce bloodstream infections and mortality by approxim<strong>at</strong>ely 50% [424]. More recently, a surprisingly strong associ<strong>at</strong>ion between ranitidine therapy in neon<strong>at</strong>es admitted to one NICU and the risk of l<strong>at</strong>e-onset bacterial sepsis was reported [425]. The mechanism for such an associ<strong>at</strong>ion is unclear, but warrants further analysis. PATHOLOGY Infants with severe and rapidly f<strong>at</strong>al sepsis generally have minimal or no histologic indic<strong>at</strong>ion of an infectious process [315,426]. Findings typical of bacteremia, such as multiple dissemin<strong>at</strong>ed abscesses of similar size, purulent vasculitis, and intravascular identific<strong>at</strong>ion of bacteria, are evident in a few infants [426]. Shock accompanying sepsis sometimes causes findings such as periventricular leukomalacia and intraventricular hemorrhage, sc<strong>at</strong>tered areas of nonzonal hep<strong>at</strong>ic necrosis, renal medullary hemorrhage, renal cortical or acute tubular necrosis, and adrenal hemorrhage and necrosis. Evidence of dissemin<strong>at</strong>ed intravascular coagulop<strong>at</strong>hy, manifested by strands of interlacing fibrin in the vessels or by a well-demarc<strong>at</strong>ed subarachnoid fibrinous hem<strong>at</strong>oma, also can be present [344,426]. The p<strong>at</strong>hology of infections of the respir<strong>at</strong>ory, genitourinary, and gastrointestinal tracts and focal suppur<strong>at</strong>ive diseases is discussed in subsequent chapters. The p<strong>at</strong>hology of neon<strong>at</strong>al meningitis [344,427,428] and brain abscess [429,430] is similar to th<strong>at</strong> in older children and adults. The major fe<strong>at</strong>ures are ventriculitis (including inflamm<strong>at</strong>ion of the choroid plexus), vasculitis, cerebral edema, infarction, cortical neuronal necrosis, and periventricular leukomalacia; chronic p<strong>at</strong>hologic fe<strong>at</strong>ures include hydrocephalus, multicystic encephalomalacia and porencephaly, and cerebral cortical and white m<strong>at</strong>ter <strong>at</strong>rophy [431]. Significant collections of purulent m<strong>at</strong>erial can be present in the sulci and subarachnoid space, particularly around the basal cisterns, of infants with meningitis. Because the fontanelles are open, exud<strong>at</strong>ive m<strong>at</strong>erial can collect around the base of the brain without a significant increase in intracranial pressure. Hydrocephalus may result from closure of the aqueduct or the foramina of the fourth ventricle by purulent exud<strong>at</strong>e or by means of inflamm<strong>at</strong>ory impairment of CSF resorption through the arachnoid channels [344,432]. Ventriculitis has been described in 20% to 90% of cases [23,344,432] and often is the reason for persistence of bacteria in CSF when obstruction ensues and for a slow clinical recovery [433]. Acute inflamm<strong>at</strong>ory cells infiltr<strong>at</strong>e the ependymal and subependymal tissues, causing destruction of the epithelial lining of the ventricles. Hemorrhage, venous thrombosis, and subdural effusions often are present. Brain abscesses and cysts in the neon<strong>at</strong>e are distinguished by the large size of the lesions and poor capsule form<strong>at</strong>ion. They occur most frequently in associ<strong>at</strong>ion with meningitis caused by C. koseri, E. sakazakii, S. marcescens, and Proteus mirabilis and usually are loc<strong>at</strong>ed in the cerebrum, involving several lobes [155,166,347,429]. These organisms characteristically give rise to a hemorrhagic meningoencephalitis caused by intense bacterial infiltr<strong>at</strong>ion of cerebral vessels and surrounding tissues. The resulting vascular occlusion is followed by infarction and widespread necrosis of cerebral tissue with liquefaction and form<strong>at</strong>ion of multiple locul<strong>at</strong>ed abscesses and cysts [347,350]. CLINICAL MANIFESTATIONS Signs of fetal distress can be the earliest indic<strong>at</strong>ion of infection in neon<strong>at</strong>es with sepsis, beginning <strong>at</strong> or soon after delivery. Fetal tachycardia in the second stage of labor was evalu<strong>at</strong>ed as a sign of infection by Schiano and colleagues [434]. Pneumonia or sepsis occurred in 3 of 8 infants with marked fetal tachycardia (>180 be<strong>at</strong>s/ min), in 7 of 32 infants with mild tachycardia (160 to 179 be<strong>at</strong>s/min), and in 1 of 167 infants with lower heart r<strong>at</strong>es. M<strong>at</strong>ernal risk factors such as prem<strong>at</strong>ure rupture of membranes, foul-smelling amniotic fluid, and evidence of acute placental inflamm<strong>at</strong>ion are associ<strong>at</strong>ed with increased risk of neon<strong>at</strong>al sepsis and should prompt detailed evalu<strong>at</strong>ion of the newborn [435,436]. A low Apgar score, suggesting distress <strong>at</strong> or before delivery, also has been correl<strong>at</strong>ed with sepsis and
associ<strong>at</strong>ed adverse outcomes in the newborn period [435,437]. Infants delivered vaginally had a 56-fold higher risk of sepsis when the Apgar score was less than 7 <strong>at</strong> 5 minutes compared with infants with higher Apgar scores [438]. Among infants born after rupture of the amniotic membranes for 24 hours or more, St. Geme and colleagues [316] found a significant increase in the risk for perin<strong>at</strong>al bacterial infection in infants with an Apgar score of less than 6 <strong>at</strong> 5 minutes, but found no associ<strong>at</strong>ion with fetal tachycardia (>160 be<strong>at</strong>s/min). The Apgar score is well characterized in term infants, but less so in prem<strong>at</strong>ure infants, who have higher <strong>at</strong>tack r<strong>at</strong>es for sepsis. Because low Apgar scores (
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