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To the Editor: The immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome, a rare disorder characterized by multiorgan autoimmunity, often results in death in infancy.1 The IPEX syndrome results from mutations in the forkhead box P3 (FOXP3) gene, which encodes a transcriptional repressor considered to be the master regulator of differentiation in CD4+ regulatory T (Treg) cells.2,3 Multiple FOXP3 mutations resulting in a range of clinical outcomes have been characterized.1–3 Since neither genetic sequencing nor protein expression correlates reliably with clinical manifestations in the IPEX syndrome,4 identification of the functional consequences of individual mutations is critical to . . .

Group B Streptococcus (GBS) is the most common cause of neonatal sepsis and meningitis. Despite antibiotics, GBS in the newborn initiates a cascade of molecular and biological events leading to altered cerebral perfusion, blood-brain barrier disruption, cerebral edema, intracranial hypertension, neurological damage, and even death. Having previously shown that GBS infection impairs cerebral blood flow autoregulation and increases prostaglandin (PG) levels, we examined the regulation of some crucial inflammatory mediators (PGs, nitric oxide (NO), tumor necrosis factor-a) in the brain and cerebral microvessels (MVs) from newborn piglets. Cyclooxygenase (COX), the key enzyme in PG biosynthesis, exists in two isoforms, COX-1 and COX-2. Both may be directly induced by NO in a model of renal inflammation. Besides its neurotransmitter role, NO is a potent vasorelaxant whose production is catalyzed by at least three distinct nitric oxide synthases (NOS) (bNOS, ecNOS, iNOS). Western blot analyses showed that the newborn (4 day old) brain expressed lower levels of COX-1 (8-fold), COX-2 (20-fold), bNOS (12-fold), and ecNOS (5-fold) than in the 1 day old. MV showed approximately equal levels of COX-2, lower levels of COX-1 (4-fold), bNOS (5-fold), and higher levels of ecNOS (20-fold) in comparison to 4-day-old cerebral MV. A 4-day-old brain expressed lower levels of bNOS (5-fold), ecNOS (10-fold), and COX-1 (2-fold) than the 6-week-old pig. COX-2 protein was undetected in a 4-day-old pig brain, but present in great excess in MV. Purified MV showed lower ecNOS (14-fold), COX-1 (2-fold), and about equal levels of bNOS and COX-2 in comparison with MV from 6-week-old pigs. Reverse transcription polymerase chain reaction analyses confirmed these results. Treatment with noo-nitro-L-arginine (LNA), a NOS inhibitor, downregulated COX-1 expression in the newborn brain and both COX-1 and COX-2 cerebral MV expression. GBS infection (10(9) colony-forming units, 0.5 mL intracerebroventricular) of sedated newborn piglets induced the expression of tumor necrosis factor-alpha in the cerebrospinal fluid after 2 hours, upregulated bNOS expression in both brain and MVs, upregulated ecNOS in MVs, and downregulated COX-1, COX-2, and ecNOS in the brain. GBS did not trigger the expression of iNOS. Our data suggest that there is a net deficiency of NOS isoforms in the immature brain and microvasculature of the 4-day-old piglet and that the differences in expression lead to the immature control of NO and PG production, rendering newborns particularly susceptible to neurological damage because of the undeveloped nature of their response mechanisms. Moreover, the GBS-induced cascade deregulates the gene expression of interacting inflammatory mediators and may cause a net vasoconstrictor/vasodilator imbalance, leading to cerebral hypertension and edema in the early stages of infection. Pharmacological manipulations of the inflammatory cascade could lead to novel therapeutic approaches for the treatment of GBS meningitis.

A heightened susceptibility to bacterial infections exists during the neonatal period. Newborn infants frequently are treated with antibiotics for suspected or proven infections. Physicians caring for these infants must familiarize themselves with the proper use of antibiotics in this special age group. This article reviews salient pharmacologic characteristics of newborn infants, emphasizing the marked differences between neonates, especially the small premature infants, and children of other ages. The excretion of antibiotics into breast milk is discussed. The pharmacologic principles of the antibiotics used more commonly in newborn infants, including mechanisms of action and resistance, antibacterial spectra, pharmacokinetics, safety, and indications for use are reviewed. Dosage schedules for use of these antibiotics in newborn infants is presented in tabular form.

Group B streptococci continue to be major perinatal pathogens, both for mothers and their infants, and are associated with significant morbidity, mortality, and its attendant cost to society. Approaches to prevention are directed toward either eliminating exposure to the organism or enhancing host resistance, that is, chemoprophylaxis and immunoprophylaxis. Intrapartum chemoprophylaxis has been shown to effectively interrupt vertical transmission of group B streptococci from the genitally colonized mother to the infant and to decrease the incidence of both maternal and early-onset neonatal group B streptococcal disease. To avoid unnecessarily exposing large numbers of colonized women to antibiotics, only those with defined risk factors should be selected for intrapartum chemoprophylaxis. This regimen is ampicillin given intravenously, 2 g initially at onset of labor or rupture of membranes, followed by 1 g every 4 hours until delivery. Risk factors include premature onset of labor or rupture of membranes before 37 weeks' gestation, rupture of membranes of more than 12 hours, intrapartum fever, group B streptococcal bacteriuria, or having previously delivered an infant with group B streptococcal disease. Detection of anogenital colonization is accomplished either by culture late in the second or early in the third trimester or by intrapartum group B streptococcal antigen testing of vaginal swabs from those previously culture-negative or not cultured. Although this approach combines the advantages of several proposed strategies, it will still miss those cases of group B streptococcal disease developing in the absence of discernible risk factors. Intrapartum prophylaxis does not prevent late-onset group B streptococcal disease. Prenatal and postnatal chemoprophylaxis have not been shown to be effective. Symptomatic infants born to mothers given chemoprophylaxis should be evaluated for neonatal sepsis and treated accordingly. This approach is also suggested for asymptomatic premature infants, those whose mothers have not received adequate prophylaxis or have previously delivered infants with group B streptococcal disease, and for twin siblings of infants developing group B streptococcal disease. Successful implementation of this approach may be limited by the availability and sensitivity of the rapid antigen test used. Immunoprophylaxis, and active immunization in particular, is the most promising method of preventing perinatal group B streptococcal disease in mothers and their infants, including late-onset disease. Immunization of pregnant women with type III polysaccharide vaccine has resulted in adequate provision of functional antibody to the infants born to responders.(ABSTRACT TRUNCATED AT 400 WORDS)

The meningeal inflammatory response to a heat-killed mutant unencapsulated strain of type III group B Streptococcus (GBS) was studied in a newborn piglet model. GBS (109 colony-forming unit equivalents) or saline (control) was inoculated intraventricularly. Serial cerebrospinal fluid measurements were done at baseline and over the course of the next 24 h for cytochemical changes and production of tumor necrosis factor (TNF) and prostaglandins. In separate experiments, we defined the time course of early changes during the first 6 h and dose response relationship over a range of inocula 106 to 109 colony-forming unit equivalents. The intraventricular inoculation of the heat-killed unencapsulated GBS induced marked leukocytosis and increased protein by 6 h. These changes were preceded by a several hundredfold increase in TNF (maximum at 2 h) and prostaglandins (maximum at 2–4 h). The early and sharp rise in TNF suggests its pivotal role in initiating the inflammatory cascade. The magnitude of the inflammatory response increased with increasing bacterial dose over the range studied. To study the effect of encapsulation of GBS in the induction of meningeal inflammation, we compared the response to the unencapsulated mutant strain with that to the encapsulated parent strain. The encapsulated strain produced much smaller inflammatory changes, and only with high doses of bacteria. The GBS cell wall appeared to be the primary bacterial product triggering inflammation. Intraventricular injection of the heat-killed unencapsulated GBS with exposed cell wall can serve as a valid model for studying neonatal meningitis.

Group B Streptococcus (GBS) meningitis in the neonate may cause early cerebral hyperemia possibly mediated by NO. We hypothesized that L-Nitroarginine (LNA), a nitric oxide synthase blocker may protect CBF autoregulation at the upper limit in GBS treated piglets. Two groups of sedated piglets (1-5 days old) were studied. The GBS group (n=7) had cerebrointraventricular injection of 0.5 ml heat killed, unencapsulated GBS(109cfu) whereas the GBS + LNA group (n=9) had GBS (109cfu) + 300 mg/kg of LNA. CBF was measured by radioactive microspheres over a range of normotension (MABP range = 50-90 mmHg) and hypertension (MABP range = 90 - 125 mmHg) induced by inflating balloon tipped catheters placed at the descending aorta, at 5 time points: 15 min pre- (baseline) and post injection of GBS with or without LNA and during normo- and hypertension. Using linear regression analysis of CBF (ml/min/100g) vs cerebral perfusion pressure (CPP), the GBS group showed a pressure passive CBF (p=0.0404, r=0.5167). In contrast, the GBS+ LNA group had CBF held constant at CPP 50-125 mmHg (r=0.16, p=0.4). Thus, NO inhibition restores CBF autoregulation at the upper limit and may reduce the amount of cerebral hyperemia in GBS meningitis.Figure

Group B streptococcal (GBS) meningitis impairs cerebral blood flow (CBF) autoregulation in newborn piglets probably via inflammatory mediators in response to GBS. We tested whether TNFα mediates early CBF impairment by GBS in 3 grps of awake sedated newborn piglets (0-5 days). Grp 1 (CTRL), n=8 had normal saline (0.5ml) via the lateral cerebral ventricle (icv), Grp 2(n=7) had heat killed unencapsulated GBS (109 cfu, 0.5ml icv) and Grp 3 had TNFα, 1,000 units icv, 0.5ml). CBF was measured over a range of mean arterial blood pressure (35-125 mmHg) induced by inflating balloon tipped catheters at the aortic root to produce cerebral hypotension or descending aorta for hypertension at 5 time points: 15 min pre (baseline) and post injection of either saline, GBS or TNFα), and during randome hypo-, normo-, and hypertension. RESULTS: 1) Grp 1, CBF and CPP (cerebral perfusion pressure) best fitted a 3rd order polynomial regression (R2=0.57,p=0.008) with constant CBF at 50-90 mmHg CPP. 2) Grp 2, GBS caused direct correlation in CBF and CPP (50-110 mmHg), r=0.52, p

NITRIC OXIDE (NO) MEDIATES CEREBRAL HYPEREMIA IN NEWBORN PIGLETS WITH GROUP B STREPTOCOCCAL (GBS) MENINGITIS. † 1072

Group B Streptococcal (GBS) meningitis impairs cerebral blood flow (CBF) autoregulation in newborn piglets. We determined whether the early impairment could be related to increased prostaglandin (PG) production and if dexamethasone and ibuprofen alter PG production in the early phase (1st 6 hrs) of GBS meningitis. Net cerebrovascular PG production (calculated as total CBF× (sagittal-arterial plasma PG concentration) of 6-keto-PGF1α (stable metabolite of prostacyclin), TXB2(thromboxane B2) and PGE2 were measured in 4 groups of piglets given either 1) saline 0.5 ml intracerebroventrically (icv, control grp, n=9), 2) GBS alone (109 cfu/0.5 ml GBS icv, n=7), or 3) GBS icv plus dexamethasone (DEX) 1 mg/kg intraarterial, ia, n=8) or 4) GBS icv plus ibuprofen (IBU) 30 mg/kg ia,n=7) during periods of normotension (MABP= 50-90 mmHg), hypotension (MABP 90mmHg). MABP was randomly adjusted by balloon tipped catheters in the aortic root and descending aorta. CBF was measured by radioactive microsphere technique and PG's were measured by radioimmunoassay. Results show that within each treatment group there was a decrease in cerebrovascular production of 6 keto-PGF1α, TXB2 and PGE2 (p < 0.05) during hypotension possibly due to relative depletion in tissue oxygen for cyclo-oxygenation of arachidonate. However, between treatment groups (Control, GBS alone, GBS+DEX, and GBS+IBU) PG production did not change with BP adjustments except for increased PGE2 during cerebral hypertension(mean±SD, PGE2=250±25 ng/min/100 g brain tissue) compared to hypotension in GBS alone (PGE2=325±30 ng/min/100 g brain, p< 0.05). Irrespective of MABP, cerebral PG production is highest for PGE2, followed by 6-keto PGF1α with no production of TXB2. Since cerebral PG production is minimally influenced by GBS with or without DEX or IBU over a wide range of cerebral perfusion pressures, we suggest that vasoactive mediators other than PG's may mediate CBF impairment in early meningitis. Thus, treatment directed to PG's may not prevent CBF impairment in neonatal GBS meningitis.

Asthma is a chronic inflammatory disease of the airways that affects a growing number of children and adolescents. Inhaled corticosteroids (ICS) are the mainstay of treatment in persistent asthma, with a stepwise approach to increasing doses of ICS depending on asthma severity and control. ICS have known local and systemic side effects, of which adrenal suppression is still under-recognized. The latter is associated with chronic exposure and higher doses, although it has rarely been reported in children receiving low doses for a short period of time. The Canadian Society of Allergy and Clinical Immunology (CSACI) therefore recommends that physicians screen for adrenal suppression in children receiving high doses for more than 6 months and to consider screening those on medium dose if the risk is deemed higher by factors that increase an individual's systemic corticosteroid exposure. Morning serum cortisol level can be used as a screening tool and abnormal results or normal results with a high index of suspicion should be confirmed with low-dose ACTH stimulation tests.