Abstract
1 Institut National de la Recherche Agronomique, Unité dÉcologie et de Physiologie du Système Digestif, Jouy en Josas, France
2 Department of Paediatrics, Azienda Ospedaliera Santa Maria Nuova, Reggio Emilia, Italy
3 Department of Paediatrics, University of Modena and Reggio Emilia, Modena, Italy
4 Department of Clinical Science and Education, Sodersjukhuset, Sachs Childrens Hospital, Karolinska Institutet, Stockholm, Sweden
5 Department of Paediatric and Adolescent Medicine, University Medical Centre, Mannheim, Germany
6 Human Nutrition Section, Division of Developmental Medicine, University of Glasgow, Yorkhill Hospitals, Glasgow, UK
7 Department of Biochemistry and Molecular Biology, University of Granada, Spain
8 Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
9 Department of Statistics and Modelling Science, University of Strathclyde, Glasgow, UK
10 Nutrition and Dietetics, School of Medicine, Flinders University, Adelaide, Australia
Although it is well established that early infant feeding has a major influence on the establishment of the gut microbiota, very little is understood about how the introduction of first solid food influences the colonization process. This study aimed to determine the impact of weaning on the faecal microbiota composition of infants from five European countries (Sweden, Scotland, Germany, Italy and Spain) which have different lifestyle characteristics and infant feeding practices. Faecal samples were collected from 605 infants approximately 4 weeks after the introduction of first solid foods and the results were compared with the same infants before weaning (6 weeks of age) to investigate the association with determining factors such as geographical origin, mode of delivery, previous feeding method and age of weaning. Samples were analysed by fluorescence in situ hybridization and flow cytometry using a panel of 10 rRNA targeted group- and species-specific oligonucleotide probes. The genus Bifidobacterium (36.5 % average proportion of total detectable bacteria), Clostridium coccoides group (14 %) and Bacteroides (13.6 %) were predominant after weaning. Similar to pre-weaning, northern European countries were associated with a higher proportion of bifidobacteria in the infant gut microbiota while higher levels of Bacteroides and lactobacilli characterized southern European countries. As before weaning, the initial feeding method influenced the Clostridium leptum group and Clostridium difficile+Clostridium perfringens species, and bifidobacteria still dominated the faeces of initially breast-fed infants. Formula-fed babies presented significantly higher proportions of Bacteroides and the C. coccoides group. The mode of birth influenced changes in the proportions of bacteroides and atopobium. Although there were significant differences in the mean weaning age between countries, this was not related to the populations of bifidobacteria or bacteroides. Thus, although the faecal microbiota of infants after first complementary foods was different to that before weaning commenced, many of the initial influences on microbiota composition were still evident.