Necrotizing Enterocolitis Is Not Associated With Sequence Variants in Antioxidant Response Genes in Premature Infants.

Reactive oxygen species mediate intestinal injury in necrotizing enterocolitis (NEC), and yet the contribution of antioxidant response (ARE) gene polymorphisms to NEC risk remains unknown. Premature infants recruited in a multicenter study were genotyped for 6 ARE variants. Among 637 infants, 52 had NEC, and 22 developed surgical NEC. Gestational age <28 weeks (P < 0.02) and African American race (P = 0.03) were associated with NEC. The NFE2L2 (rs6721961), SOD2 (rs4880), GSTP1 (rs1695), NQO1 (rs1800566), GCLC (rs17883901), and HMOX1 (rs2071747) variants were not associated with medical or surgical NEC. This study does not support a role for common deleterious ARE variants in NEC.

Antioxidant response genes sequence variants and BPD susceptibility in VLBW infants.

BACKGROUND: Lung injury resulting from oxidative stress contributes to bronchopulmonary dysplasia (BPD) pathogenesis. Nuclear factor erythroid-2 related factor-2 (NFE2L2) regulates cytoprotective responses to oxidative stress by inducing enzymes containing antioxidant response elements (ARE). We hypothesized that ARE genetic variants will modulate susceptibility or severity of BPD in very-low-birth-weight (VLBW) infants. METHODS: Blood samples obtained from VLBW infants were used for genotyping variants in the SOD2, NFE2L2, GCLC, GSTP1, HMOX1, and NQO1 genes. SNPs were genotyped utilizing TaqMan probes (Applied Biosystems (ABI), Grand Island, NY), and data were analyzed using the ABI HT7900. Genetic dominance and recessive models were tested to determine associations between SNPs and BPD. RESULTS: In our cohort (n = 659), 284 infants had BPD; 135 of whom developed severe BPD. Presence of the hypomorphic NQO1 SNP (rs1800566) in a homozygous state was associated with increased BPD, while presence of the NFE2L2 SNP (rs6721961) was associated with decreased severe BPD in the entire cohort and in Caucasian infants. In regression models that adjusted for epidemiological confounders, the NQO1 and the NFE2L2 SNPs were associated with BPD and severe BPD, respectively. CONCLUSION: Genetic variants in NFE2L2-ARE axis may contribute to the variance in liability to BPD observed in preterm infants. These results require confirmation in independent cohorts.

The NFKB1 (g.-24519delATTG) variant is associated with necrotizing enterocolitis (NEC) in premature infants.

OBJECTIVE: While it is known that gene-environment interactions contribute to necrotizing enterocolitis (NEC) pathogenesis, characterization of genetic risk-factors that can predict NEC in preterm infants remains nascent. We hypothesized that altered intestinal immune responses arising from sequence variation in the toll-like receptor (TLR) pathway genes contribute to NEC susceptibility. MATERIALS AND METHODS: Very low birth weight (VLBW) infants were recruited prospectively in a multi-center, cohort study involving collection of blood samples along with collation of clinical information. DNA obtained from blood samples was used to genotype nine single nucleotide polymorphisms (SNPs) in eight TLR pathway genes by single-base extension. Prevalence of the variant allele was compared between cases and controls using Fisher's exact test. RESULTS: In our cohort of 271 infants, 15 infants (5.6%) developed NEC, and five died from it. Infants with NEC were less mature (P < 0.001), and were more likely to be African-American (P = 0.007). SNPs in the TLR2, TLR4, TLR5, TLR9, IRAK1, and TIRAP genes were not associated with NEC. The NFKB1 (g.-24519delATTG) variant was present in all infants with NEC but only in 65% of infants without NEC (P = 0.003), while the NFKBIA (g.-1004A>G) variant was present in 13.3% of infants with NEC but in 49% of infants without NEC (P = 0.007). After correcting for multiple comparisons, the NFKB1 and NFKBIA variants remained associated with NEC (P < 0.05). CONCLUSIONS: These data suggest that TLR genetic variants can alter susceptibility to NEC in VLBW infants and support the hypothesis that genetically programmed differences in the innate immune response contribute to NEC pathogenesis.

Cohort study of the pathogenesis and molecular epidemiology of catheter-related bloodstream infection in neonates with peripherally inserted central venous catheters.

OBJECTIVE: To better define the pathogenesis of catheter-related bloodstream infection (BSI) in neonates with peripherally inserted central venous catheters (PICCs) to guide the development of more effective strategies for prevention. DESIGN: Prospective nested cohort study. SETTING: Level III neonatal intensive care unit in a community hospital. METHODS: During a randomized trial to assess the safety and efficacy of a prophylactic vancomycin-heparin catheter-lock solution for the prevention of catheter-related BSI in neonates with PICCs, we performed cultures of peripheral and catheter-drawn blood samples, and quantitative cultures of catheter hub samples if BSI was suspected clinically. We performed semiquantitative cultures of the catheter tip and the catheter hub and the skin at the insertion site when the catheter was removed. Molecular subtyping by pulsed-field electrophoresis was used to determine the probable pathogenesis of all BSIs due to coagulase-negative staphylococci (CoNS); for BSIs caused by other microorganisms, epidemiologic concordance was based on speciation and antibiograms. Catheter-related BSI was considered extraluminally acquired if concordance was demonstrable solely between isolates recovered from the catheter tip and the blood, independent of concordance with isolates recovered from the insertion site. Catheter-related BSI was considered intraluminally acquired if concordance was demonstrated only between isolates recovered from the catheter hub and the blood. The source of the infection was considered indeterminate if both concordance patterns were present. RESULTS: Nosocomial BSI was identified in 23 of the 82 neonates in the cohort. Fifteen of these infections, 14 of which were caused by CoNS, were considered definite or probable catheter-related BSIs. Catheter-related BSI was intraluminally acquired in 10 (67%) of 15 patients, extraluminally acquired in 3 (20%), and indeterminate in 2 (13%). CONCLUSIONS: Most catheter-related BSIs in neonates with PICCs are caused by CoNS and derive from intraluminal contamination. Strategies for prevention of catheter-related BSI directed at this predominant mechanism of infection are most likely to be effective.

The effect of a prolonged time interval between antenatal corticosteroid administration and delivery on outcomes in preterm neonates: a cohort study.

OBJECTIVE: This study was undertaken to determine whether the neonatal benefit of a single complete course of antenatal corticosteroids diminishes when delivery is remote from administration (> 14 days). STUDY DESIGN: This retrospective 2 center cohort trial included women who received a single complete course of antenatal corticosteroids and delivered a viable singleton infant between 26 and 34 weeks of gestation. Patients were divided into 1 of 2 groups on the basis of the interval from first corticosteroid dose to delivery (2-14 days and > 14 days). Neonatal outcomes among treatment groups were stratified by gestational age at delivery (< 28 weeks, > or = 28 weeks). Regression models were used to control for potential confounders. RESULTS: Three hundred fifty-seven pregnancies were included, of which 98 women delivered at > 14 days after antenatal corticosteroids. Neonates at > or = 28 weeks of gestation and who delivered at > 14 days after antenatal corticosteroids were more likely to require surfactant therapy (60% vs 48%; p = .02) and to require ventilatory support for > 24 hours (58% vs 46%; P = .02). Differences in outcomes between groups remained in regression models that were controlled for confounders. There was no significant difference between treatment groups for neonates who delivered at < 28 weeks of gestation. Rates of survival without chronic lung disease and intraventricular hemorrhage were similar between groups. CONCLUSION: A time interval of > 14 days between the administration of antenatal corticosteroids and delivery is associated with an increased risk for ventilatory support and surfactant use in neonates who deliver at > 28 weeks of gestation.

Effect of dose on response to adrenocorticotropin in extremely low birth weight infants.

CONTEXT: Various cosyntropin doses are used to test adrenal function in premature infants, without consensus on appropriate dose or adequate response. OBJECTIVE: The objective of this study was to test the cortisol response of extremely low birth weight infants to different cosyntropin doses and evaluate whether these doses differentiate between groups of infants with clinical conditions previously associated with differential response to cosyntropin. DESIGN: The design was a prospective, nested study conducted within a randomized clinical trial of low-dose hydrocortisone from November 1, 2001, to April 30, 2003. SETTING: The setting was nine newborn intensive care units. PATIENTS: The patients included infants with 500-999 g birth weight. INTERVENTION: The drug used was cosyntropin, at 1.0 or 0.1 microg/kg, given between 18 and 28 d of birth. MAIN OUTCOME MEASURE: We measured the cortisol response to cosyntropin. RESULTS: Two hundred seventy-six infants were tested. Previous hydrocortisone treatment did not suppress basal or stimulated cortisol values. Cosyntropin, at 1.0 vs. 0.1 microg/kg, yielded higher cortisol values (P < 0.001) and fewer negative responses (2 vs. 21%). The higher dose, but not the lower dose, showed different responses for girls vs. boys (P = 0.02), infants receiving enteral nutrition vs. not (P < 0.001), infants exposed to chorioamnionitis vs. not (P = 0.04), and those receiving mechanical ventilation vs. not (P = 0.02), as well as a positive correlation with fetal growth (P = 0.03). A response curve for the 1.0-microg/kg dose for infants receiving enteral nutrition (proxy for clinically well infants) showed a 10th percentile of 16.96 microg/dl. Infants with responses less than the 10th percentile had more bronchopulmonary dysplasia and longer length of stay. CONCLUSIONS: A cosyntropin dose of 0.1 microg/kg did not differentiate between groups of infants with clinical conditions that affect response. We recommend 1.0 microg/kg cosyntropin to test adrenal function in these infants.

A TLR5 (g.1174C > T) variant that encodes a stop codon (R392X) is associated with bronchopulmonary dysplasia.

Current evidence supports a major role for inherited factors in determining bronchopulmonary dysplasia (BPD) susceptibility. The Toll-like receptor (TLR) family of proteins maintain pulmonary homeostasis in the developing lung by aiding pathogen recognition and clearance, regulating inflammation, and facilitating reparative tissue growth. We hypothesized that sequence variation in the TLR pathway genes would alter the susceptibility/severity of BPD in preterm infants. Very low birth-weight infants were recruited prospectively in a multi-center study involving collection of blood samples and clinical information. Nine TLR pathway single-nucleotide polymorphisms were genotyped using a multiplexed single-base extension assay. BPD outcomes were compared among infants with and without the variant allele using Chi-square or Fisher's exact tests. In our cohort (n = 289), 66 (23.6%) infants developed BPD, out of which 32 (11.2%) developed severe BPD. The TLR5 (g.1174C > T) variant was associated with BPD (P = 0.03) and severe BPD (P = 0.004). The TIRAP (g.2054C > T) variant was associated with BPD (P = 0.04). Infants heterozygous for the X-linked IRAK1 (g.6435T > C) variant had a lower incidence of BPD compared to infants homozygous for either the reference or variant allele (P = 0.03). In regression models that controlled for potential epidemiological confounders, the TIRAP variant was associated with BPD, and the TLR5 variant was associated with severe BPD. Our data support the hypothesis that aberrant pathogen recognition in premature infants arising from TLR pathway genetic variation can contribute to BPD pathogenesis.

Strategies to prevent ventilator-associated pneumonia in neonates.

Ventilator-associated pneumonia (VAP) is one of the leading causes of preventable morbidity and mortality in neonatal intensive care units. This review examines the epidemiology and pathogenesis of VAP in neonates as well as the dilemmas faced by caregivers to diagnose and prevent VAP.

Strategies to prevent bacterial and fungal infection in the neonatal intensive care unit.

Hospital-acquired infections are one of the leading causes of preventable morbidity and mortality in neonatal intensive care units (NICUs). Device-related infections, such as catheter-associated blood stream infections (CABSIs) and ventilator-associated pneumonia (VAP), are the most common nosocomial infections. This review examines the pathogenesis of CABSIs and methods, widely accepted and novel, that can be used to help prevent them. Strategies to prevent fungal infections, which are often associated with the presence of a central venous catheter, are also reviewed. Finally, the dilemmas in the diagnosis and prevention of VAP in the NICU are discussed.

A vancomycin-heparin lock solution for prevention of nosocomial bloodstream infection in critically ill neonates with peripherally inserted central venous catheters: a prospective, randomized trial.

OBJECTIVE: Critically ill neonates are at high risk for vascular catheter-related bloodstream infection (CRBSI), most often caused by coagulase-negative staphylococci. Most CRBSIs with long-term devices derive from intraluminal contaminants. The objective of this study was to ascertain the safety and the efficacy of a vancomycin-heparin lock solution for prevention of CRBSI. METHODS: A prospective, randomized double-blind trial was conducted during 2000-2001 at a community hospital level III NICU. Very low birth weight and other critically ill neonates with a newly placed peripherally inserted central venous catheter were randomized to have the catheter locked 2 or 3 times daily for 20 or 60 minutes with heparinized normal saline (n = 43) or heparinized saline that contained vancomycin 25 microg/mL (n = 42). The origin of each nosocomial bloodstream infection (BSI) was studied by culturing skin, catheter hubs, and implanted catheter segments and blood cultures, demonstrating concordance by restriction-fragment DNA subtyping. Surveillance axillary and rectal cultures were performed to detect colonization by vancomycin-resistant organisms. The main outcome measures were (1) CRBSIs and (2) colonization or infection by vancomycin-resistant Gram-positive bacteria. RESULTS: Two (5%) of 42 infants in the vancomycin-lock group developed a CRBSI as compared with 13 (30%) of 43 in the control group (2.3 vs 17.8 per 1000 catheter days; relative risk: 0.13; 95% confidence interval: 0.01-0.57). No vancomycin-resistant enterococci or staphylococci were recovered from any cultures. Vancomycin could not be detected in the blood of infants who did not receive systemic vancomycin therapy. Twenty-six neonates (8 vancomycin-lock group, 18 control group) had at the end of a catheter-lock period asymptomatic hypoglycemia that resolved promptly when glucose-containing intravenous fluids were restarted. CONCLUSIONS: Prophylactic use of a vancomycin-heparin lock solution markedly reduced the incidence of CRBSI in high-risk neonates with long-term central catheters and did not promote vancomycin resistance but was associated with asymptomatic hypoglycemia. The use of an anti-infective lock solution for prevention of CRBSI with long-term intravascular devices has achieved proof of principle and warrants selective application in clinical practice.

Prophylaxis of early adrenal insufficiency to prevent bronchopulmonary dysplasia: a multicenter trial.

BACKGROUND: Infants developing bronchopulmonary dysplasia (BPD) show decreased cortisol response to adrenocorticotropic hormone. A pilot study of low-dose hydrocortisone therapy for prophylaxis of early adrenal insufficiency showed improved survival without BPD at 36 weeks' postmenstrual age, particularly in infants exposed to histologic chorioamnionitis. METHODS: Mechanically ventilated infants with birth weights of 500 to 999 g were enrolled into this multicenter, randomized, masked trial between 12 and 48 hours of life. Patients received placebo or hydrocortisone, 1 mg/kg per day for 12 days, then 0.5 mg/kg per day for 3 days. BPD at 36 weeks' postmenstrual age was defined clinically (receiving supplemental oxygen) and physiologically (supplemental oxygen required for O2 saturation > or =90%). RESULTS: Patient enrollment was stopped at 360 patients because of an increase in spontaneous gastrointestinal perforation in the hydrocortisone-treated group. Survival without BPD was similar, defined clinically or physiologically, as were mortality, head circumference, and weight at 36 weeks. For patients exposed to histologic chorioamnionitis (n = 149), hydrocortisone treatment significantly decreased mortality and increased survival without BPD, defined clinically or physiologically. After treatment, cortisol values and response to adrenocorticotropic hormone were similar between groups. Hydrocortisone-treated infants receiving indomethacin had more gastrointestinal perforations than placebo-treated infants receiving indomethacin, suggesting an interactive effect. CONCLUSIONS: Prophylaxis of early adrenal insufficiency did not improve survival without BPD in the overall study population; however, treatment of chorioamnionitis-exposed infants significantly decreased mortality and improved survival without BPD. Low-dose hydrocortisone therapy did not suppress adrenal function or compromise short-term growth. The combination of indomethacin and hydrocortisone should be avoided.