Relationship between the presence of newborn and the house dust endotoxin Virginie Doyen a , Anne-Britt Johansson b , Laurence Hanssens c , Nathalie Dehennin d , Duc Huy Phong Dinh e , Georges Casimir c , Olivier Michel a, ⁎ a Clinic of Immuno-allergology, CHU Brugmann, Université Libre de Bruxelles (ULB), Belgium b Neonatal Intensive Care Unit, Hôpital Universitaire Des Enfants Reine Fabiola, HUDERF (ULB), Belgium c Department of Pulmonology, Allergology and Cystic Fibrosis, Hôpital Universitaire Des Enfants Reine Fabiola, HUDERF (ULB), Belgium d Pediatric Department, CHU Saint-Pierre (ULB), Brussels, Belgium e Department of Immunology, Pham Ngoc Thach University of Medicine (PNTU), Ho Chi Minh City, Vietnam abstract article info Article history: Received 9 March 2011 Received in revised form 7 September 2011 Accepted 8 September 2011 Available online 4 October 2011 Keywords: Endotoxin House dust Newborn Background: Exposure to house dust endotoxin induces of airways' inflammation. Endotoxin are produced by the Gram-negative bacteria, which are released into the stools and could contaminate domestic environment. Objective: The newborn could contaminate his mattress by endotoxin. Methods: The dusts of mattress and carpets of 97 newborn' dwellings were sampled at birth and after six months of life. Samplings were made in the bedroom from the baby and in the second place where the baby spent the longer time. The endotoxin concentration was measured by a quantitative Limulus assay and the bacterial contamination was evaluated using 3 selective agar media. Results: Endotoxin concentration at birth was positively associated with the presence of both sibling and the number of inhabitants (p b 0.01). At 6 months of life, the endotoxin concentration raised significantly not only in the mattresses (from a median of 17.6 (ranges: 0.4–346.7) to 79.6 (3.8–518.8) EU/mg) (p b 0.0001), but also in the dust from the second place where the baby is sleeping (from 20.4 (0.8–226.3) to 101.8 (6.5– 634.3) EU/mg) (p b 0.001). Importantly, there was no change in endotoxin concentration from the carpets dust, and the environmental dwelling characteristics remained unchanged. The total bacterial contamination was also positively associated with endotoxin concentration in newborn mattress at birth (p b 0.01) and showed a significant increase at 6 months of life of the newborn (p b 0.01). Conclusion: The newborn is a significant source of house dust's endotoxin. © 2011 Published by Elsevier B.V. 1. Introduction Endotoxins are pro-inflammatory constituents of the Gram-negative bacteria outer membrane. They are present in the house dust and in some occupational environments. Endotoxin exposure has been associated with chronic obstructive pulmonary diseases in occu- pational settings (Vogelzang et al., 1998), asthma severity in domestic settings (Michel et al., 1996; Rizzo et al., 1997), asthma prevalence (Thorne et al., 2005) and wheezing in infants (Park et al., 2001). An acute inhalation of endotoxin has been shown to amplify the allergic inflammation (Eldridge and Peden, 2000). Paradoxally, the house dust (HD) endotoxin concentration was reported to be lower in homes of allergen-sensitized that in non- sensitized children and the endotoxin concentration in children's mattresses was inversely correlated to the occurrence of hay fever, allergic asthma and atopic sensitization (Braun-Fahrländer et al., 2002). Few data are available on the environmental factors associated with the endotoxin contamination. The presence of animals and the number of inhabitants, have been associated with the risk of a high level of endotoxin (Gehring et al., 2004; Thorne et al., 2009; Giovannangelo et al., 2007). Seasonal variation, temperature and humidity have incon- stant effects on the dust endotoxin level (Park et al., 2000). The Gram- negative bacteria are growing in environments in presence of water or high level of humidity or are released from animals and/or humans (Horak et al., 1996). A wide variety of Gram-negative bacteria inhabits the normal body surfaces (the skin, oral cavity, respiratory tract, vagina, urinary tract and gastrointestinal tract). For example, the gut contains more than 1 kg of Gram-negative bacteria, which are released into the stools and could contaminate domestic environment (Täubel et al., 2009). We hypothesized that the newborn could be a source of envi- ronmental endotoxin. The endotoxin contamination of the mat- tresses and carpets in newborn's dwellings was measured at birth and after 6 months of life and related with several dwellings characteristics. Science of the Total Environment 409 (2011) 5313–5317 ⁎ Corresponding author at: Clinique d'Immuno-allergologie / CHU Brugmann (ULB), 4 pl Van Gehuchten, B-1020 Brussels, Belgium. Tel.: +32 2 477 3664; fax: +32 2 477 22 76. E-mail address: omichel@ulb.ac.be (O. Michel). 0048-9697/$ – see front matter © 2011 Published by Elsevier B.V. doi:10.1016/j.scitotenv.2011.09.026 Contents lists available at SciVerse ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv