Coagulase-negative staphylococcal sepsis as a predictor of bronchopulmonary dysplasia

Altered Gut Microbiome and Fecal Immune Phenotype in Early Preterm Infants With Leaky Gut

Intestinal barrier immaturity, or "leaky gut", is the proximate cause of susceptibility to necrotizing enterocolitis in preterm neonates. Exacerbated intestinal immune responses, gut microbiota dysbiosis, and heightened barrier injury are considered primary triggers of aberrant intestinal maturation in early life. Inordinate host immunity contributes to this process, but the precise elements remain largely uncharacterized, leaving a significant knowledge gap in the biological underpinnings of gut maturation. In this study, we investigated the fecal cytokine profile and gut microbiota in a cohort of 40 early preterm infants <33-weeks-gestation to identify immune markers of intestinal barrier maturation. Three distinct microbiota types were demonstrated to be differentially associated with intestinal permeability (IP), maternal breast milk feeding, and immunological profiles. The Staphylococcus epidermidis- and Enterobacteriaceae-predominant microbiota types were associated with an elevated IP, reduced breast milk feeding, and less defined fecal cytokine profile. On the other hand, a lower IP was associated with increased levels of fecal IL-1α/β and a microbiota type that included a wide array of anaerobes with expanded fermentative capacity. Our study demonstrated the critical role of both immunological and microbiological factors in the early development of intestinal barrier that collectively shape the intestinal microenvironment influencing gut homeostasis and postnatal intestinal maturation in early preterm newborns.

An Update on the Prevention and Management of Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is a common morbidity affecting preterm infants and is associated with substantial long-term disabilities. There has been no change in the incidence of BPD over the past 20 years, despite improvements in survival and other outcomes. The preterm lung is vulnerable to injuries occurring as a result of invasive ventilation, hyperoxia, and infections that contribute to the development of BPD. Clinicians caring for infants in the neonatal intensive care unit use multiple therapies for the prevention and management of BPD. Non-invasive ventilation strategies and surfactant administration via thin catheters are treatment approaches that aim to avoid volutrauma and barotrauma to the preterm developing lung. Identifying high-risk infants to receive postnatal corticosteroids and undergo patent ductus arteriosus closure may help to individualize care and promote improved lung outcomes. In infants with established BPD, outpatient management is complex and requires coordination from several specialists and therapists. However, most current therapies used to prevent and manage BPD lack solid evidence to support their effectiveness. Further research is needed with appropriately defined outcomes to develop effective therapies and impact the incidence of BPD.

Late-Onset Sepsis as a Risk Factor for Bronchopulmonary Dysplasia in Extremely Low Birth Weight Infants: A Nationwide Cohort Study

This study aimed to determine the effect of late-onset sepsis (LOS) on the development of bronchopulmonary dysplasia (BPD) in extremely low birth weight (ELBW) infants. A prospective cohort study was performed using data collected from 64 centres registered in the Korean national registry. LOS was defined as a positive blood culture and antibiotics treatment after 72 hours of life and prior to 36 weeks postmenstrual age (PMA). Data on the causative organisms were collected and analysed for respiratory outcomes. Among the 1,434 ELBW infants who survived to 36 weeks PMA, 481 (34%) developed LOS caused by bacteria (n = 405), fungi (n = 28), or both (n = 48). The incidence of BPD was significantly associated with LOS in both the entire cohort and the propensity score-matched cohort. Two or more LOS episodes were a risk factor for BPD. The impact of multiple episodes of LOS on BPD was prominent in infants who received mechanical ventilation for two weeks or less. The estimated odds ratios for BPD and severe BPD were greater with fungal LOS than with bacterial LOS. In conclusion, LOS, particularly complicated by multiple episodes and/or fungi, was a risk factor for BPD in ELBW infants.

Beyond sepsis: Staphylococcus epidermidis is an underestimated but significant contributor to neonatal morbidity

Staphylococcus epidermidis accounts for the majority of cases of neonatal sepsis. Moreover, it has been demonstrated to be associated with neonatal morbidities, such as bronchopulmonary dysplasia (BPD), white matter injury (WMI), necrotizing enterocolitis (NEC) and retinopathy of prematurity (ROP), which affect short-term and long-term neonatal outcome. Imbalanced inflammation has been considered to be a major underlying mechanism of each entity. Conventionally regarded as a harmless commensal on human skin, S. epidermidis has received less attention than its more virulent relative Staphylococcus aureus. Particularities of neonatal innate immunity and nosocomial environmental factors, however, may contribute to the emergence of S. epidermidis as a significant nosocomial pathogen. Neonatal host response to S. epidermidis sepsis has not been fully elucidated. Evidence is emerging regarding the implication of S. epidermidis sepsis in the pathogenesis of neonatal inflammatory diseases. This review focuses on the interplay among S. epidermidis, neonatal innate immunity and inflammation-driven organ injury.

Heteroresistant Vancomycin Intermediate Coagulase Negative Staphylococcus in the NICU: A Systematic Review

CONTEXT

NICUs in the province of Québec have seen an increase in hVICoNS, detected in the clinical laboratory.

OBJECTIVE

To investigate the clinical relevance of hVICoNS on the course of infection, and to determine the prevalence of hVICoNS sepsis in the NICU.

METHODS

We searched MEDLINE, EMBASE, and PubMed from 1 January 1980 to 1 July 2016. Both observational and interventional studies were considered eligible if they provided data on hVICoNS in the NICU population. Two investigators independently reviewed studies for data extraction. Data extracted included: number of CoNS cultures, prevalence of hVICoNS, and clonality of strains.

RESULTS

Of the 613 studies identified, 19 studies were reviewed, and 5 studies included in the final review. No studies addressed the clinical significance of hVICoNS in the NICU. The prevalence of hVICoNS in the NICU varied greatly, ranging from 2.3% to 100%.

LIMITATIONS

Publication bias could not be assessed, and risk of bias in some of the included studies due to small sample size and poor methods reporting. The quality of all included studies was low according to GRADE criteria, and the inclusion criteria restricted to either English or French studies.

CONCLUSIONS

Our review suggests that heteroresistance to vancomycin is much more common than previously believed. Our search however did not identify any studies that explicitly assessed any clinical implications of hVICoNS infections, thereby highlighting the need for research to assess the true impact of hVICoNS infection and to determine its significance on patient mortality and morbidity in the NICU.

Sustained Reduction in Bloodstream Infections in Infants at a Large Tertiary Care Neonatal Intensive Care Unit

BACKGROUND

Bloodstream infections (BSI) cause significant morbidity and mortality among hospitalized infants.

PURPOSE

Reduction of BSIs has emerged as an important patient safety goal. Implementation of central line insertion bundles, standardized line care protocols, and health care provider education programs have reduced BSI in NICUs around the country. The ability of large tertiary care centers to decrease nosocomial infections, including BSI, has been demonstrated. However, long-term BSI reductions in infants are not well documented. We sought to demonstrate that a low incidence of BSI can be maintained over time in a tertiary care NICU.

RESULTS

Baseline BSI incidence for infants admitted to the NICU was 5.15 and 6.08 episodes per 1000 infant-days in 2005 and 2006, respectively. After protocol implementation, the incidence of BSI decreased to 2.14/1000 infant-days and 2.44/1000 infant-days in 2008 and 2009, respectively. Yearly incidence remained low over the next 4 years and decreased even further to 0.20 to 0.45 infections per 1000 infant-days. This represents a 92% decrease in BSI over a period of more than 5 years.

IMPLICATIONS FOR PRACTICE

Implementation of a nursing-led comprehensive infection control initiative can effectively produce and maintain a reduction in the incidence of BSI in infants at a large tertiary care NICU.

IMPLICATIONS FOR RESEARCH

Additional research is needed to effectively expand prevention of central line-associated BSIs to BSIs of all etiologies.

No survival benefit with empirical vancomycin therapy for coagulase-negative staphylococcal bloodstream infections in infants

BACKGROUND

Coagulase-negative Staphylococcus (CoNS) is the most common cause of bloodstream infections (BSI) in hospitalized infants. CoNS BSI is most reliably treated with vancomycin; however, concerns about side effects and promoting resistance often delay empirical vancomycin therapy until culture results become available.

METHODS

All infants with CoNS BSI discharged from 348 neonatal intensive care units managed by the Pediatrix Medical Group from 1997 to 2012 were identified. Empirical vancomycin therapy was defined as vancomycin exposure on the day of the first positive blood culture. Delayed vancomycin therapy was defined as vancomycin exposure 1-3 days after the first positive blood culture. We used multivariable logistic regression with random effects for site to evaluate the association between the use of empirical vancomycin therapy versus delayed vancomycin therapy and 30-day mortality, controlling for gestational age, small-for-gestational age status, postnatal age on the day of the first positive culture, oxygen requirement, ventilator support and inotropic support on the day the first positive culture was obtained.

RESULTS

A total of 4364 infants with CoNS BSI were identified; 2848 (65%) were treated with empirical vancomycin. The median postnatal age at first positive culture was 14 days (interquartile range: 9, 21). Unadjusted 30-day mortality was similar for infants treated with empirical vancomycin and infants treated with delayed vancomycin therapy [166/2848 (6%) vs. 69/1516 (4%); P = 0.08]. There was no significant difference in 30-day mortality on multivariable analysis [odds ratio: 1.14 (0.84, 1.56)]. The median duration of bacteremia was 1 day longer for infants with delayed vancomycin therapy [4 days (interquartile range: 2, 6) vs. 3 days (2, 5); P < 0.0001].

CONCLUSIONS

The median duration of bacteremia was 1 day longer in infants with CoNS BSI who received delayed vancomycin therapy. Despite this finding, empirical vancomycin therapy for CoNS BSI was not associated with improved mortality.

Molecular epidemiology of coagulase-negative Staphylococcus carriage in neonates admitted to an intensive care unit in Brazil

Background

Nasal colonization with coagulase-negative Staphylococcus (CoNS) has been described as a risk factor for subsequent systemic infection. In this study, we evaluated the genetic profile of CoNS isolates colonizing the nares of children admitted to a neonatal intensive care unit (NICU).

Methods

We assessed CoNS carriage at admittance and discharge among newborns admitted to a NICU from July 2007 through May 2008 in one of the major municipalities of Brazil. Isolates were screened on mannitol salt agar and tryptic soy broth and tested for susceptibility to antimicrobials using the disc diffusion method. Polymerase chain reaction (PCR) was used to determine the species, the presence of the mecA gene, and to perform SCCmec typing. S. epidermidis and S. haemolyticus isolated from the same child at both admission and discharge were characterized by PFGE.

Results

Among 429 neonates admitted to the NICU, 392 (91.4%) had nasal swabs collected at both admission and discharge. The incidence of CoNS during the hospitalization period was 55.9% (95% confidence interval [CI]: 50.9-60.7). The most frequently isolated species were S. haemolyticus (38.3%) and S.epidermidis (38.0%). Multidrug resistance (MDR) was detected in 2.2% and 29.9% of the CoNS isolates, respectively at admittance and discharge (p = 0.053). The mecA gene was more prevalent among strains isolated at discharge (83.6%) than those isolated at admission (60%); overall, SCCmec type I was isolated most frequently. The length of hospitalization was associated with colonization by MDR isolates (p < 0.005). Great genetic diversity was observed among S. epidermidis and S. haemolyticus.

Conclusions

NICU represents an environment of risk for colonization by MDR CoNS. Neonates admitted to the NICU can become a reservoir of CoNS strains with the potential to spread MDR strains into the community.

Neonatal host defense against Staphylococcal infections

Preterm infants are especially susceptible to late-onset sepsis that is often due to Gram-positive bacterial infections resulting in substantial morbidity and mortality. Herein, we will describe neonatal innate immunity to Staphylococcus spp. comparing differences between preterm and full-term newborns with adults. Newborn innate immunity is distinct demonstrating diminished skin integrity, impaired Th1-polarizing responses, low complement levels, and diminished expression of plasma antimicrobial proteins and peptides, especially in preterm newborns. Characterization of distinct aspects of the neonatal immune response is defining novel approaches to enhance host defense to prevent and/or treat staphylococcal infection in this vulnerable population.

Systemic responses of preterm newborns with presumed or documented bacteraemia

AIM

To compare the frequency of elevated concentrations of inflammation-related proteins in the blood of infants born before the 28th week of gestation who had documented bacteraemia and those who had presumed (antibiotic-treated but culture-negative) bacteraemia to those who had neither.

METHODS

The subjects of this study are the 868 infants born at 14 institutions for whom information about protein measurements on at least two of the three protocol days (days 1, 7, and 14) was available and who did not have Bell stage 3 necrotizing enterocolitis or isolated bowel perforation, which were strongly associated with bacteraemia in this sample.

RESULTS

Newborns with presumed early (week 1) bacteraemia had elevated concentrations of only a few inflammation-related proteins, while those who had presumed late (weeks 2-4) bacteraemia did not have any elevations. In contrast, newborns who had documented early bacteraemia had a moderately strong signal, while those who had documented late bacteraemia had a stronger signal with more protein concentrations elevated on two separate occasions a week apart.

CONCLUSIONS

Culture-confirmed early and late bacteraemia are accompanied/followed by systemic inflammatory responses not seen with presumed early and late bacteraemia.

Excess soluble vascular endothelial growth factor receptor-1 in amniotic fluid impairs lung growth in rats: linking preeclampsia with bronchopulmonary dysplasia

Epidemiological studies have shown that maternal preeclampsia (PE) increases the risk of bronchopulmonary dysplasia (BPD), but the underlying mechanism is unknown. Soluble vascular endothelial growth factor receptor-1 (soluble VEGFR1, known as soluble fms-like tyrosine kinase 1, or sFlt-1), an endogenous antagonist of vascular endothelial growth factor (VEGF), is markedly elevated in amniotic fluid and maternal blood in PE. Therefore, we hypothesized that antenatal exposure to excess sFlt-1 disrupts lung development through impaired VEGF signaling in utero, providing a mechanistic link between PE and BPD. To determine whether increased sFlt-1 in amniotic fluid is sufficient to cause sustained abnormalities of lung structure during infancy, sFlt-1 or saline was injected into amniotic sacs of pregnant Sprague-Dawley rats at 20 days of gestation (term, 22 days). After birth, pups were observed through 14 days of age for study. We found that intra-amniotic sFlt-1 treatment decreased alveolar number, reduced pulmonary vessel density, and caused right and left ventricular hypertrophy in 14-day-old rats. In addition, intra-amniotic sFlt-1 treatment suppressed activation of lung VEGF receptor-2 and increased apoptosis in endothelial and mesenchymal cells in the newborn lung. We conclude that exposure to excess sFlt-1 in amniotic fluid during late gestation causes sustained reductions in alveolarization and pulmonary vascular growth during infancy, accompanied by biventricular hypertrophy suggesting pulmonary and systemic hypertension. We speculate that impaired VEGF signaling in utero due to exposure of high amniotic fluid levels of sFlt-1 in PE disrupts lung growth and contributes to the increased risk of BPD in infants born to mothers with PE.

Frequency and clinical correlates of radiographic patterns of bronchopulmonary dysplasia in very low birth weight infants by term age

Our aim was to study the frequency and clinical correlates of two radiographic patterns of bronchopulmonary dysplasia (BPD), the cystic BPD (cBPD) and the leaky lung syndrome (LLS). Radiographic findings of BPD from sixth day of life until term in a cohort of 82 very low birth weight (VLBW) infants were evaluated and scored independently by a neonatologist and a paediatric radiologist. Data on prenatal factors and events during the first hospitalisation were collected prospectively. Forty-four (53.7%) infants showed radiographic evidence of BPD, 19 (23.2%) cBPD and 25 (30.5%) LLS. In multivariate analysis, the best predictors for radiographic BPD were oxygen dependency at 28 days (odds ratio (OR) 10.2 [95% confidence interval (CI) 2.49-41.4]), more than 2 days on ventilator (OR 10.4 [95% CI 1.8-61.5]) and volume expanders in the first 2 h (OR 7.36 [95% CI 1.32-41.2]). During the first week of life, infants with radiographic BPD received less energy per kilogram (p < 0.001) and more daily fluids per kilogram of body weight (p = 0.013). Sixty-two percent of the infants with radiographic BPD were not oxygen dependent at 36 weeks postmenstrual age (PMA). Seventeen (89.5%) of the 19 infants who needed oxygen supplementation at 36 weeks PMA also had abnormal chest X-rays.

CONCLUSIONS

Radiographic BPD findings appeared to be common in VLBW infants. In addition to the well-known respiratory risk factors (oxygen and ventilator therapy), poor nutrition and excessive fluid administration in early life seem to be significantly associated with radiological findings of lung injury in these patients.

A quantitative analysis of Ureaplasma urealyticum and Ureaplasma parvum compared with host immune response in preterm neonates at risk of developing bronchopulmonary dysplasia

Multiplex, real-time PCR for the identification of Ureaplasma urealyticum and Ureaplasma parvum was performed on nucleic acids extracted from sequential endotracheal aspirates obtained from preterm neonates born at <29 weeks of gestation and ventilated for more than 48 h admitted to two level 3 neonatal intensive care units. Specimens were obtained shortly after birth and sequentially up until extubation. One hundred fifty-two specimens (93.8%) contained material suitable for analysis. Ureaplasma spp. were identified in 5 of 13 neonates studied. In most cases, the DNA load of the detected Ureaplasma species was low and decreased over time. In addition, changes in detectable Ureaplasma species DNA did not relate to changes in the inflammatory marker C-reactive protein (CRP) or respiratory status. All but two blood samples obtained at times of suspected sepsis were culture positive for other microorganisms; the species cultured were typically coagulase-negative staphylococci and were associated with increased levels of CRP (>10 mg/liter). This study was limited by the small number of patients examined and does not have the power to support or contradict the hypothesis that postnatal lung infection with Ureaplasma parvum is causally related to bronchopulmonary dysplasia (BPD) or adverse respiratory outcomes after preterm birth. However, in this study, increases in CRP levels were not associated with patients in whom Ureaplasma parvum was detected, in contrast to the detection of other bacterial species.

Coagulase-negative staphylococcal infections in the neonatal intensive care unit

BACKGROUND

Coagulase-negative staphylococci (CoNS) are the most commonly isolated pathogens in the neonatal intensive care unit (NICU). CoNS infections are associated with increased morbidity, including neurodevelopmental impairment.

OBJECTIVE

To describe the epidemiology of CoNS infections in the NICU. To determine mortality among infants with definite, probable, or possible CoNS infections.

METHODS

We performed a retrospective cohort study of all blood, urine, and cerebrospinal fluid cultures from samples obtained from infants aged <121 postnatal days.

SETTING

A total of 248 NICUs managed by the Pediatrix Medical Group from 1997 to 2009.

RESULTS

We identified 16,629 infants with 17,624 episodes of CoNS infection: 1,734 (10%) definite, 3,093 (17%) probable, and 12,797 (73%) possible infections. Infants with a lower gestational age and birth weight had a higher incidence of CoNS infection. When controlling for gestational age, birth weight, and 5-minute Apgar score, we found that infants with definite, probable, or possible CoNS infection had lower mortality (odds ratio [OR], 0.74 [95% confidence interval {CI}: 0.61, 0.89], 0.68 [95% CI, 0.59, 0.79], and 0.69 [95% CI, 0.63, 0.76], respectively) compared with infants who had negative culture results (P = .001). No significant difference in overall mortality was found in infants who had definite CoNS infection compared with those who had probable or possible CoNS infection (OR, 0.93 [95% CI, 0.75, 1.16] and 0.85 [95% CI, 0.70, 1.03], respectively).

CONCLUSIONS

CoNS infection was strongly related to lower gestational age and birth weight. Infants with clinical sepsis and culture-positive CoNS infection had lower mortality rates than infants with clinical sepsis and negative blood culture results. No difference in mortality between infants with a diagnosis of definite, probable, or possible CoNS infection was observed.

Endothelial function in children with a history of premature prolonged rupture of membranes and bronchopulmonary dysplasia--a pilot study

AIM

To investigate vascular function in children with a neonatal history of generalised inflammation indicated by premature prolonged rupture of membranes (PPROM) and bronchopulmonary dysplasia (BPD).

METHODS

Children born at <or=30 weeks 1994-2000 were investigated at a present age of 6-12 years. Twenty-eight children participated and were divided into two groups with regard to BPD/no BPD (n=15/13) and PPROM/no PPROM (n=10/18). Vascular endothelial function was assessed by acetylcholine (ACh)-induced skin vasodilatation.

RESULTS

Maximum ACh-induced skin perfusion was statistically significantly lower in the PPROM group compared with the non-PPROM group (p=0.045) after adjustment for confounders. We found no association between BPD and maximum ACh-induced skin perfusion (p=0.404), after adjustment for confounders.

CONCLUSION

A neonatal history of prolonged premature rupture of membranes was associated with later impairment of vascular endothelial function in childhood. This association was not observed with BPD. Some forms of perinatal inflammation may be associated with later cardiovascular function.

The role of inflammation and infection in the development of chronic lung disease of prematurity

CLD is a significant cause of infant morbidity and mortality. The lung injury is multifactorial in origin with supplemental oxygen and ventilatory damage being only part of the picture. Antenatal and postnatal infection and inflammation are also important in the development of CLD, although their precise role has still to be fully ascertained. In the future, therapeutic strategies need to be considered to decrease the incidence and severity of CLD. In particular a definitive trial investigating the role of antibiotics against Ureaplasma urealyticum in preventing CLD needs to be performed. Increased use of newer microbiological methods will also improve our understanding of the role of infection in CLD and further guide research and clinical management.