Although it has been generally assumed that new- borns are born germ free and that initial gut colonization occurs during birth, more recent studies suggest that fetal colonization begins prior to birth. Besides a possible prenatal transfer of maternal bacteria to fetus, other major determinants for neonatal gut colonization are mode of delivery, mode of feeding and perinatal antibiotic exposure. Several studies have shown effects of delivery mode on the gut micro- biota composition of newborns. Generally, vaginally born infants are first colonized by bacteria from the maternal vagina, mainly characterized by a prevalence of Prevotella, Sneathia, and Lactobacillus genera, also including bacteria present in the maternal gut, while the gut microbiota of infants born by Cesarean (C)-section more often resembles maternal skin and oral microbiota, with a prevalence of Propionibacterium spp., Corynebacterium spp., and Streptococcus spp. Moreover, infants born by C-section have delayed colonization of Bacteroides spp., and lower microbial diversity throughout the first 2 years of life. In a previous study, we also have evaluated the relation between intestinal ecosystem of the newborn and mode of delivery by means of a molecular biology approach, collecting fecal samples on day 3 of life in 23 infants born vaginally and in 23 infants delivered by C-section. The intestinal microbiota of neonates delivered by C-section actually appeared to be less diverse, in terms of bacteria species, than the microbiota of vaginally delivered infants, being characterized by an absence of Bifidobacteria spp. Conversely, vaginally delivered neonates, although showing individual microbial profiles, were characterized by predominant groups such as B. longum and B. catenulatum. However, the effects on species diversity between different modes of delivery are reported to progressively disappear by the first year of life, when infant microbiome becomes more similar to the maternal one. It has been suggested that the early gut colonization may have long-term medical consequences: indeed, C-section delivered babies seems to display higher incidence of celiac disease, obesity and asthma, with some implications on the maturation of the immune system, in terms of lower blood levels of T-helper cell-related chemokines, possibly due to the reduced gut colonization of Bacteroides genus. Perinatal antibiotic exposure is another major determinant of early gut microbial composition in newborns. Thanks to new molecular techniques currently available, we now have proof of antibiotic-induced intestinal dysbiosis, in turn associated with intestinal and plasma lipid profile alterations. Several studies have also demonstrated that antibiotic exposure in early infancy is associated with increased risk of developing overweight/obesity, as well as asthma, wheezing and inflammatory bowel disease later in life. There has been accumulating evi- dence that intestinal microbiota play a key role in mod- ulating the cross-talk between brain and gut (the so called “brain-gut-enteric microbiota axis”), by means of the synthesis of many neuroactive molecules such as serotonin, melatonin, adrenaline, dopamine, ace- tylcholine and GABA. Finally, mode of feeding also plays an important role in influencing early intestinal microbiota. Breastfeeding is undoubtedly the best way to promote the healthy development of human off- spring as it is considered to be the optimal source for all the nutritional and functional factors that infants need. Several studies have recently proven that human milk is not sterile and it is the predominant source for establishing a “healthy microbiome” in the newborn. Milk microbial composition changes over the lactation period, being colostrum predominantly colonized by Staphylococci spp., Streptococci spp., and Lactococci spp., whereas milk samples collected later on harbor oral cavity related bacteria, perhaps due to frequent interaction with the infant’s oral microbiota. The milk microbial colonization is likely derived from mother’s gut and the elevation of progesterone levels seems to be a major cause for increasing gut permeability, thus facilitating the bacterial passage to the bloodstream and then to mammary glands. The infant’s early gut colonization is therefore modulated both by human milk microbiome and by other unique nutritional components of human milk, such as oligosaccharides and lactoferrin, also known as prebiotic or bifido- genic factors. As a consequence, there are significant differences in the gut microbiota composition of breast-fed versus formula-fed infants. Several studies have pointed out that Bifidobacteria are the most abundant organisms in breast-fed infant guts, whereas the gut microbiota of formula-fed infants is domi- nated by Enterococci spp. and Clostridia spp., with more species diversity. In conclusion, although the complex interaction between host and intestinal microbiota is not fully clarified yet, neonatal early gut microbial colonization seems to be a crucial step at a critical age for modulating infant’s healthy immunological, hormonal and metabolic development.

THE EARLY GUT COLONIZATION IN NEW- BORNS / Biasucci, G. - ELETTRONICO. - 5:2(2016), pp. e050246.12-e050246.13. (Intervento presentato al convegno 12th International Workshop on Neonatology, Cagliari(Italy) - October 19th-22nd, 2016 tenutosi a Cagliari (Italy) nel October 19th-22nd, 2016) [10.7363/050246].

THE EARLY GUT COLONIZATION IN NEW- BORNS

Biasucci G
2016-01-01

Abstract

Although it has been generally assumed that new- borns are born germ free and that initial gut colonization occurs during birth, more recent studies suggest that fetal colonization begins prior to birth. Besides a possible prenatal transfer of maternal bacteria to fetus, other major determinants for neonatal gut colonization are mode of delivery, mode of feeding and perinatal antibiotic exposure. Several studies have shown effects of delivery mode on the gut micro- biota composition of newborns. Generally, vaginally born infants are first colonized by bacteria from the maternal vagina, mainly characterized by a prevalence of Prevotella, Sneathia, and Lactobacillus genera, also including bacteria present in the maternal gut, while the gut microbiota of infants born by Cesarean (C)-section more often resembles maternal skin and oral microbiota, with a prevalence of Propionibacterium spp., Corynebacterium spp., and Streptococcus spp. Moreover, infants born by C-section have delayed colonization of Bacteroides spp., and lower microbial diversity throughout the first 2 years of life. In a previous study, we also have evaluated the relation between intestinal ecosystem of the newborn and mode of delivery by means of a molecular biology approach, collecting fecal samples on day 3 of life in 23 infants born vaginally and in 23 infants delivered by C-section. The intestinal microbiota of neonates delivered by C-section actually appeared to be less diverse, in terms of bacteria species, than the microbiota of vaginally delivered infants, being characterized by an absence of Bifidobacteria spp. Conversely, vaginally delivered neonates, although showing individual microbial profiles, were characterized by predominant groups such as B. longum and B. catenulatum. However, the effects on species diversity between different modes of delivery are reported to progressively disappear by the first year of life, when infant microbiome becomes more similar to the maternal one. It has been suggested that the early gut colonization may have long-term medical consequences: indeed, C-section delivered babies seems to display higher incidence of celiac disease, obesity and asthma, with some implications on the maturation of the immune system, in terms of lower blood levels of T-helper cell-related chemokines, possibly due to the reduced gut colonization of Bacteroides genus. Perinatal antibiotic exposure is another major determinant of early gut microbial composition in newborns. Thanks to new molecular techniques currently available, we now have proof of antibiotic-induced intestinal dysbiosis, in turn associated with intestinal and plasma lipid profile alterations. Several studies have also demonstrated that antibiotic exposure in early infancy is associated with increased risk of developing overweight/obesity, as well as asthma, wheezing and inflammatory bowel disease later in life. There has been accumulating evi- dence that intestinal microbiota play a key role in mod- ulating the cross-talk between brain and gut (the so called “brain-gut-enteric microbiota axis”), by means of the synthesis of many neuroactive molecules such as serotonin, melatonin, adrenaline, dopamine, ace- tylcholine and GABA. Finally, mode of feeding also plays an important role in influencing early intestinal microbiota. Breastfeeding is undoubtedly the best way to promote the healthy development of human off- spring as it is considered to be the optimal source for all the nutritional and functional factors that infants need. Several studies have recently proven that human milk is not sterile and it is the predominant source for establishing a “healthy microbiome” in the newborn. Milk microbial composition changes over the lactation period, being colostrum predominantly colonized by Staphylococci spp., Streptococci spp., and Lactococci spp., whereas milk samples collected later on harbor oral cavity related bacteria, perhaps due to frequent interaction with the infant’s oral microbiota. The milk microbial colonization is likely derived from mother’s gut and the elevation of progesterone levels seems to be a major cause for increasing gut permeability, thus facilitating the bacterial passage to the bloodstream and then to mammary glands. The infant’s early gut colonization is therefore modulated both by human milk microbiome and by other unique nutritional components of human milk, such as oligosaccharides and lactoferrin, also known as prebiotic or bifido- genic factors. As a consequence, there are significant differences in the gut microbiota composition of breast-fed versus formula-fed infants. Several studies have pointed out that Bifidobacteria are the most abundant organisms in breast-fed infant guts, whereas the gut microbiota of formula-fed infants is domi- nated by Enterococci spp. and Clostridia spp., with more species diversity. In conclusion, although the complex interaction between host and intestinal microbiota is not fully clarified yet, neonatal early gut microbial colonization seems to be a crucial step at a critical age for modulating infant’s healthy immunological, hormonal and metabolic development.
2016
THE EARLY GUT COLONIZATION IN NEW- BORNS / Biasucci, G. - ELETTRONICO. - 5:2(2016), pp. e050246.12-e050246.13. (Intervento presentato al convegno 12th International Workshop on Neonatology, Cagliari(Italy) - October 19th-22nd, 2016 tenutosi a Cagliari (Italy) nel October 19th-22nd, 2016) [10.7363/050246].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11381/2931018
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