title: Preterm infant gut colonization in the neonatal ICU and complete restoration 2 years later.
abstract: Preterm infants in a neonatal intensive care unit (NICU) are exposed to multidrug-resistant bacteria previously adapted to the hospital environment. The aim of the present study was to characterize the bacterial antibiotic-resistant high-risk lineages colonizing preterm infants during their NICU stay and their persistence in faeces after 2 years. A total of 26 preterm neonates were recruited between October 2009 and June 2010 and provided 144 faecal samples. Milk samples (86 mother's milk, 35 human donor milk and 15 formula milk) were collected at the same time as faecal samples. An additional faecal sample was recovered in 16 infants at the age of 2 years. Samples were plated onto different selective media, and one colony per morphology was selected. Isolates were identified by 16S rDNA nucleotide sequence and MALDI-TOF. Antibiotic susceptibility (agar dilution), genetic diversity (RAPD, PFGE and MLST) and virulence factors (only in enterococcal and staphylococcal isolates) were determined by PCR. A high proportion of antibiotic-resistant high-risk clones was detected in both faecal and milk samples during the NICU admittance. Almost all infants were colonized by Enterococcus faecalis ST64 and Enterococcus faecium ST18 clones, while a wider genetic diversity was observed for the Gram-negative isolates. Multidrug-resistant high-risk clones were not recovered from the faecal samples of the 2-year-olds. In conclusion, the gut of preterm infants admitted to the NICU might be initially colonized by antibiotic-resistant and virulent high-risk lineages, which are later replaced by antibiotic-susceptible community ones.
authors.affiliation: Departmento de Nutrición, Bromatología y Tecnología de los Alimentos, Universidad Complutense de Madrid, Madrid, Spain; Instituto Ramón y Cajal de Investigaciones Sanitarias (IRYCIS), Madrid, Spain.
authors.forename: L
authors.initials: L
authors.lastname: Moles
authors.affiliation: Departmento de Nutrición, Bromatología y Tecnología de los Alimentos, Universidad Complutense de Madrid, Madrid, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Gómez
authors.affiliation: Departmento de Nutrición, Bromatología y Tecnología de los Alimentos, Universidad Complutense de Madrid, Madrid, Spain; ProbiSearch, S.L., Tres Cantos, Madrid, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Jiménez
authors.affiliation: Departmento de Nutrición, Bromatología y Tecnología de los Alimentos, Universidad Complutense de Madrid, Madrid, Spain; ProbiSearch, S.L., Tres Cantos, Madrid, Spain.
authors.forename: L
authors.initials: L
authors.lastname: Fernández
authors.affiliation: Servicio de Neonatología Hospital Universitario 12 de Octubre, Madrid, Spain; Red de Salud Materno-Infantil y del Desarrollo (SAMID), Instituto Carlos III, Madrid, Spain.
authors.forename: G
authors.initials: G
authors.lastname: Bustos
authors.affiliation: Servicio de Microbiología, Hospital Universitario 12 de Octubre, Madrid, Spain; Servicio de Microbiología, Hospital Universitario Ramón y Cajal, Madrid, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Chaves
authors.affiliation: Instituto Ramón y Cajal de Investigaciones Sanitarias (IRYCIS), Madrid, Spain; Servicio de Microbiología, Hospital Universitario Ramón y Cajal, Madrid, Spain; Spanish Network for Research in Infectious Diseases (REIPI), Instituto de Salud Carlos III, Madrid, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Cantón
authors.affiliation: Departmento de Nutrición, Bromatología y Tecnología de los Alimentos, Universidad Complutense de Madrid, Madrid, Spain; ProbiSearch, S.L., Tres Cantos, Madrid, Spain.
authors.forename: J M
authors.initials: JM
authors.lastname: Rodríguez
authors.affiliation: Instituto Ramón y Cajal de Investigaciones Sanitarias (IRYCIS), Madrid, Spain; Servicio de Microbiología, Hospital Universitario Ramón y Cajal, Madrid, Spain; Spanish Network for Research in Infectious Diseases (REIPI), Instituto de Salud Carlos III, Madrid, Spain. Electronic address: rosacampo@yahoo.com.
authors.forename: R
authors.initials: R
authors.lastname: Del Campo
mesh_terms: D002675:Child, Preschool; D016000:Cluster Analysis; D016172:DNA Fingerprinting; D004275:DNA, Ribosomal / Q000235:genetics; D024881:Drug Resistance, Bacterial; D005243:Feces / Q000382:microbiology; D005260:Female; D005500:Follow-Up Studies; D000069196:Gastrointestinal Microbiome; D041981:Gastrointestinal Tract / Q000382:microbiology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007234:Infant, Premature; D007363:Intensive Care Units, Neonatal; D008297:Male; D064307:Microbiota; D008969:Molecular Sequence Data; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S
keywords: Antibiotic resistance; gut microbiota; human milk; nosocomial high-risk clones; preterm infants; virulence factors