Christèle Gras-Leguen

Development of intestinal microbiota in infants and its impact on health.

Throughout the human lifetime, the intestinal microbiota performs vital functions, such as barrier function, metabolic reactions, trophic effects, and maturation of the hosts innate and adaptive immune responses. Development of the intestinal microbiota in infants is characterized by rapid and large changes in microbial abundance, diversity, and composition. These changes are influenced by medical, cultural, and environmental factors such as mode of delivery, diet, familial environment, diseases, and therapies used. Thus, it is nearly impossible to define a universal standard for intestinal colonization and development of the intestinal microbiota. This review discusses recent data on the early colonization of the gut by microbial species, development of the intestinal microbiota, and its impact on health.

Intrauterine infection induces programmed cell death in rabbit periventricular white matter

An association between chorioamnionitis and periventricular leukomalacia has been reported in human preterm infants. However, whether this link is causal has not been convincingly established, and the underlying molecular mechanisms remain unclear. The objective of this study was to establish a reproducible model of cerebral white matter disease in preterm rabbits after intrauterine infection. Escherichia coli was inoculated into both uterine horns of laparotomized pregnant rabbits when gestation was 80% complete. The fetuses were delivered by cesarean section and killed 12, 24, or 48 h after the inoculation. Programmed cell death in the white matter was evaluated by hematoxylin-eosin-saffron staining and in situ fragmented DNA labeling (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling). In a first group of 14 pregnant rabbits not treated with antibiotics, all fetuses delivered 48 h after inoculation were stillborn, whereas fetuses extracted 12 or 24 h after inoculation were alive. No significant cell death was detected in the live fetuses compared with the control noninfected rabbits. In a second group of five pregnant rabbits treated with ceftriaxone initiated 24 h after the inoculation and continued until cesarean section was performed 48 h after inoculation, 13 fetuses were alive, but all showed evidence of extensive programmed cell death in the white matter by hematoxylin-eosin-saffron staining and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling. White matter damage became histologically detectable only 48 h after inoculation. Three of the 13 brains displayed periventricular white matter cysts mimicking human cystic periventricular leukomalacia. The high reproducibility of white matter damage in our model should permit further studies aimed at unraveling the molecular mechanisms of periventricular leukomalacia.

Patterns of cerebral inflammatory response in a rabbit model of intrauterine infection-mediated brain lesion

Although the fetal inflammatory response syndrome seems crucial to the association between intrauterine infection and white matter disease in human preterm infants, the underlying mechanisms remain unclear. Using our previously described rabbit model of cerebral cell death in the white matter and hippocampus induced by intrauterine Escherichia coli infection, we investigated inflammatory and astroglial responses in placenta and brain tissues, in correlation with cell death distribution. Brains and placentas were studied 12, 24, or 48 h following intrauterine inoculation of E. coli or saline (groups G12, G24, and G48). Diffuse monocyte-macrophage infiltrates positive for inducible nitric oxide synthase (i-NOS) were significantly more marked in G24 and G48 placentas than in controls. In the G48 fetuses with both diffuse cell death and focal periventricular white matter cysts mimicking cystic periventricular leukomalacia, a strong rabbit macrophage and inducible nitric oxide synthase immunostaining was observed at the border of these cystic lesions. In contrast, in the fetuses with only diffuse and significant cell death, no inflammatory or astroglial responses were detected in the white matter or hippocampus. Cell death was accompanied by i-NOS immunostaining in the hippocampus but not the white matter. Hippocampal cells positive for i-NOS usually displayed a neuronal phenotype. In this model, focal white matter cysts are accompanied by a robust inflammatory response, and diffuse cell death, which may mimic the white matter and hippocampal damage seen in very and extremely pre-term infants, occur in the absence of a detectable brain inflammatory response.

Eradication of methicillin-resistant Staphylococcus aureus in a neonatal intensive care unit: which measures for which success?

BACKGROUND Various strategies for controlling methicillin-resistant Staphylococcus aureus (MRSA) outbreaks in neonatal intensive care units (NICUs) have been tried, with varying levels of success. We report a MRSA outbreak occurring between April 2004 and August 2007 in a 24-bed NICU in a large university hospital. We describe the difficulties involved in implementing measures to control the MRSA outbreak and the possible contribution of each measure. METHODS Cases were defined as neonates with MRSA obtained from either clinical cultures or surveillance cultures (from the anterior nares). Systematic screening of neonates for colonization was performed only between February and December 2005. Successive control strategies included barrier precaution and isolation in individual rooms, mupirocine ointment for neonates and health care workers, cohort isolation, hand hygiene observation, and staff training. RESULTS During the routine surveillance culture period (February to December 2005; 48 weeks), 46 neonates were found to be positive for MRSA and were treated with mupirocin. After December 2005, the outbreak was controlled, but the ongoing spread was not eradicated; 9 sporadic MRSA cases were detected by clinical culture up to August 2007. CONCLUSION The widespread use of mupirocine in staff and patients did not control the outbreak and is not recommended. The later control appeared to coincide with increased hand hygiene audits and training for staff, along with appropriate cohort isolation of neonates and cohort nursing.

Effects of hydroxyethyl starch on cardiac output in hypotensive neonates: a comparison with isotonic saline and 5% albumin.

AIM: To evaluate the effects of hydroxyethyl starch (6% HES 200/0.5) on cardiac output in hypotensive neonates with low cardiac output and absence of myocardial dysfunction. METHODS: In a prospective randomized blinded trial, 21 hypotensive neonates (mean gestational age of 29+/-3 wk) were randomly allocated to receive infusions of either 5% albumin (albumin group), isotonic saline (saline group) or hydroxyethyl starch (HES group). Infants had to show low cardiac output and an absence of myocardial dysfunction for inclusion in the study. Cardiac output was assessed by Doppler-derived mean aortic flow velocity. RESULTS: Ten minutes after infusion, 67% of all infants had more than a 10% increase in cardiac output. Increases in mean aortic flow velocity (m/s; median and range) were 0.05 (-0.02, +0.07), 0.03 (-0.03, +0.12) and 0.03 (-0.04, +0.11) for the albumin, saline and HES groups, respectively (p = 0.79). The percentage of blood pressure normalization (95% confidence interval) was 86% (60-100) in the albumin group, 57% (20-94) in the saline group and 71% (37-100) in the HES group (p = 0.50). CONCLUSION: This study did not provide evidence that hydroxyethyl starch is more efficient than isotonic saline or albumin.

Effect of maternal antibiotic treatment on fetal periventricular white matter cell death in a rabbit intrauterine infection model

Aim: To evaluate the effects of maternal antibiotic treatment on fetal brain cell death in a rabbit intrauterine infection model. Methods: After Escherichia coli uterine‐horn inoculation in 22 pregnant rabbits, followed at various times by ceftriaxone and caesarean section, cell death in white matter (histology and fragmented DNA staining) from fetuses killed at extraction was compared across groups using the Mantel‐Haenszel test and Fishers exact test for small numbers. Results: White matter cell death was consistently present at 48 h, with ceftriaxone initiation at 24 h (group 1), detectable at 84 but not 60 h, with ceftriaxone initiation at 12 h, and significantly reduced at 84 h with ceftriaxone initiation at 6 h (60% vs 100% in group 1, p < 0.001, Fishers exact test).

When should clinicians suspect group A streptococcus empyema in children? A multicentre case–control study in French tertiary care centres

Background The incidence of invasive group A streptococcus (GAS) infections is increasing worldwide, whereas there has been a dramatic decrease in pneumococcal invasive diseases. Few data describing GAS pleural empyema in children are available. Objective To describe the clinical and microbiological features, management and outcome of GAS pleural empyema in children and compare them with those of pneumococcal empyema. Design, setting and patients Fifty children admitted for GAS pleural empyema between January 2006 and May 2013 to 8 hospitals participating in a national pneumonia survey were included in a descriptive study and matched by age and centre with 50 children with pneumococcal empyema. Results The median age of the children with GAS pleural empyema was 2 (range 0.1–7.6) years. Eighteen children (36%) had at least one risk factor for invasive GAS infection (corticosteroid use and/or current varicella). On admission, 37 patients (74%) had signs of circulatory failure, and 31 (62%) had a rash. GAS was isolated from 49/50 pleural fluid samples and from one blood culture. The commonest GAS genotype was emm1 (n=17/22). Two children died (4%). Children with GAS empyema presented more frequently with a rash (p<0.01), signs of circulatory failure (p=0.01) and respiratory disorders (p=0.02) and with low leucocyte levels (p=0.04) than children with pneumococcal empyema. Intensive care unit admissions (p<0.01), drainage procedures (p=0.04) and short-term complications (p=0.01) were also more frequent in patients with GAS empyema. Conclusions Pleural empyema following varicella or presenting with rash, signs of circulatory failure and leucopenia may be due to GAS. These features should prompt the addition to treatment of an antitoxin drug, such as clindamycin.

Effects of hydroxyethyl starch on cardiac output in hypotensive neonates: A comparison with isotonic saline and 5% albumin: Hydroxyethyl starch in neonates

Aim: To evaluate the effects of hydroxyethyl starch (6% HES 200/0.5) on cardiac output in hypotensive neonates with low cardiac output and absence of myocardial dysfunction. Methods: In a prospective randomized blinded trial, 21 hypotensive neonates (mean gestational age of 29±3 wk) were randomly allocated to receive infusions of either 5% albumin (albumin group), isotonic saline (saline group) or hydroxyethyl starch (HES group). Infants had to show low cardiac output and an absence of myocardial dysfunction for inclusion in the study. Cardiac output was assessed by Doppler‐derived mean aortic flow velocity. Results: Ten minutes after infusion, 67% of all infants had more than a 10% increase in cardiac output. Increases in mean aortic flow velocity (m/s; median and range) were 0.05 (−0.02, +0.07), 0.03 (−0.03, +0.12) and 0.03 (−0.04, +0.11) for the albumin, saline and HES groups, respectively (p = 0.79). The percentage of blood pressure normalization (95% confidence interval) was 86% (60–100) in the albumin group, 57% (20–94) in the saline group and 71% (37–100) in the HES group (p = 0.50). Conclusion: This study did not provide evidence that hydroxyethyl starch is more efficient than isotonic saline or albumin.