Newborn baby digestive tract: Difference between revisions
| Line 12: | Line 12: | ||
===Factors Affecting the Microflora Composition=== | ===Factors Affecting the Microflora Composition=== | ||
The mode of delivery determines the nature of microbes ingested by the infant. Through normal vaginal birth, an infant is exposed to the mother’s vaginal and fecal flora, which results in the colonization of ''[[Lactobacillus]]'', ''[[Bifidobacterium]]'', ''[[Escherichia coli]]'', and ''[[Enterococcus]]''. However, an infant delivered by Caesarian section is exposed to a different assortment of microbes, such as ''[[Clostridium]]'' and ''[[Streptococcus]]'', which are acquired from the tools used. These microbes can establish and colonize rapidly within the sterile digestive tract, because there are no pre-existing microbes to compete with. | The mode of delivery determines the nature of microbes ingested by the infant. Through normal vaginal birth, an infant is exposed to the mother’s vaginal and fecal flora, which results in the colonization of ''[[Lactobacillus]]'', ''[[Bifidobacterium]]'', ''[[Escherichia coli]]'', and ''[[Enterococcus]]''. However, an infant delivered by Caesarian section is exposed to a different assortment of microbes, such as ''[[Clostridium]]'' and ''[[Streptococcus]]'', which are acquired from the tools used. These microbes can establish and colonize rapidly within the sterile digestive tract, because there are no pre-existing microbes to compete with. Microbes are able to communicate with their environment as well as others by quorum sensing. Quorum sensing serves as a defense mechanism against colonization by new strains of bacteria ('''T''') | ||
| Line 30: | Line 30: | ||
|Infants are less prone to infections due to a large amount of Bifidobacteria. || Infants are more prone to infections due to the lower amount of Bifidobacteria. This can result in a higher risk of diarrhea and allergies. | |Infants are less prone to infections due to a large amount of Bifidobacteria. || Infants are more prone to infections due to the lower amount of Bifidobacteria. This can result in a higher risk of diarrhea and allergies. | ||
|} | |} | ||
==Microbial Diversity== | ==Microbial Diversity== | ||
Revision as of 22:29, 28 August 2008
Before birth, the tract of the fetus is sterile, but within hours of birth, the baby acquires a complex collection of microorganisms which populate the mouth—then eventually the full length of the digestive tract will be colonized. The development of specific microorganisms is influenced by the exposure to certain factors such as maternal microbiota, environmental contact, mode of delivery and the infant’s diet.
The Niche: Newborn Baby Digestive Tract
The newborn baby digestive tract includes the esophagus, stomach, small intestine, large intestine, and rectum. Although the mouth is not considered part of the digestive tract, it plays a critical role in food breakdown and provides access for microbes to enter and colonize the infant’s digestive tract. Beyond the mouth, the esophagus serves as a passage for the microbes to progress further down the digestive tract, pass the stomach and into the intestines where the microbes can establish and initiate colonization. Of all the parts of the digestive tract, the intestines are where the majority of the microflora resides. Finally, the rectum serves as an exit for microbes to leave the digestive tract.
Physical Conditions
The pH of an infant’s stomach ranges approximately from 2 to 5. Initially the pH of the stomach is less acidic, but the presence of microbes, such as Streptococcus and Lactobacillus, and their metabolic activities create a more acidic environment. However, further down the digestive tract the acidity of the environment decreases.
The infant’s stomach is a well-oxygenated area because air swallowed with food arrives in the stomach within moments of ingestion. The facultative anaerobes established in the stomach utilize the available oxygen, resulting in an oxygen-reduced environment for the obligate anaerobic microbes in the intestines.
Factors Affecting the Microflora Composition
The mode of delivery determines the nature of microbes ingested by the infant. Through normal vaginal birth, an infant is exposed to the mother’s vaginal and fecal flora, which results in the colonization of Lactobacillus, Bifidobacterium, Escherichia coli, and Enterococcus. However, an infant delivered by Caesarian section is exposed to a different assortment of microbes, such as Clostridium and Streptococcus, which are acquired from the tools used. These microbes can establish and colonize rapidly within the sterile digestive tract, because there are no pre-existing microbes to compete with. Microbes are able to communicate with their environment as well as others by quorum sensing. Quorum sensing serves as a defense mechanism against colonization by new strains of bacteria (T)
The microflora composition of the infant digestive tract is largely influenced by the dietary intake of the infant. A difference can be observed in the development of microflora between breast-fed and formula-fed infants.
| Breast-Fed Infants | Formula-Fed Infants |
|---|---|
| The digestive tract is colonized by primarily Bifidobacteria. | The digestive tract is colonized predominantly of Bacteroides with some Bifidobacteria; but over time the difference in the number of colonies of the two genera decreases. |
| Human milk has antimicrobial factors that lower the growth of facultative anaerobes. | There exists a more complex flora consisting largely of facultative and obligate anaerobes, such as Enterobacteria, Streptococcus and Clostridium. |
| Intestinal lumen is acidified more easily because human milk does not serve as an efficient buffer. | Intestinal lumen is closer to a neutral pH. |
| Infants are less prone to infections due to a large amount of Bifidobacteria. | Infants are more prone to infections due to the lower amount of Bifidobacteria. This can result in a higher risk of diarrhea and allergies. |
Microbial Diversity
Bifidobacterium
Bifidobacterium species colonize in great numbers in the infant digestive tract, regardless if the infant is breast-fed or formula-fed. By utilizing the proteins in breast-milk, they become established. A rough range of 50%-90% of human milk oligosaccharides pass through infants undigested. Bifidobacterium is able to break down these undigested sugars and obtain energy and nutrients for growth. They situate themselves by associating with the intestinal wall, either directly attaching to the epithelium or entrapping themselves in the mucous layer of the epithelium. The most common Bifidobacterium species in infants are Bifidobacterium infantis, Bifidobacterium breve, and Bifidobacterium longum. However, Bifidobacterium infantis is specifically unique to the infant’s digestive tract. They are Gram-positive microbes and are oxygen intolerant; hence, they colonize within the intestines rather than the stomach. Being Gram-positive bacteria, Bifidobacterium infantis have a thick cell wall for extra protection from other residing microbes within the intestines. Increased colonization of Bifidobacterium in the large intestine, and its interaction with Lactobacilli, results in enhanced carbohydrate fermentation. Fermentation results in an increased production of acetic acid, butyric acid, and lactic acid, which creates an acidic barrier against pathogenic bacteria.
Lactobacillus
Lactobacilli are Gram-positive rods that can be found throughout the digestive tract, but is predominantly present in the large intestine. It can infiltrate an infant’s sterile digestive tract by means of contact with the mucosal surface of the mother’s vagina or from the mother’s breast milk. Lactobacilli are second only to Bifidobacteria in dominating the microbiota of breast-fed infants. The most common species of Lactobacilli found in infants is Lactobacillus acidophilus. Lactobacilli contribute to digestion, stimulate the immune system, and inhibit the growth of pathogens. Lactobacilli break down sugars, mainly lactose, into lactic acid using the enzyme β-galactosidase. Sugar metabolism provides nutrients and energy for its growth and survival. The accumulation of lactic acid lowers the environmental pH, which inhibits the growth of pathogenic bacteria, such as Helicobacter pylori. Lactobacilli can also regulate their enzymatic activity to maintain a suitable living condition. Lactobacilli can also inhibit growth of other bacteria by competing with them for nutrients and epithelial adhesion sites on the intestinal wall. Lactobacilli are also commonly used as probiotics, supplements containing bacteria that are beneficial to humans.
Streptococcus
Streptococci are spherical, Gram-positive, facultative anaerobic bacteria found in the neonatal intestinal tract. It is one of the initial microbes that colonize the digestive tract after birth. This anaerobe utilizes the oxygen present creating a reduced environment which allows for growth of obligate anaerobic bacteria. Streptococci also ferment sugars into lactic acid. Streptococcus agalactiae is known as Group B Streptococci (GBS) and is known to cause meningitis and sepsis in infants.
Escherichia coli
Clostridium
Clostridium difficile is a Gram-positive, sporeforming, obligate anaerobe. This species of Clostridium is potentially pathogenic and can cause infant diarrhea.
Current Research
Enter summaries of the most recent research. You may find it more appropriate to include this as a subsection under several of your other sections rather than separately here at the end. You should include at least FOUR topics of research and summarize each in terms of the question being asked, the results so far, and the topics for future study. (more will be expected from larger groups than from smaller groups)
References
Edited by [Coco Chin , Jeremy Dayrit , Hanaah Fannin , Angela Ho , Chon Ieng , Min-jeong Suh ], students of Rachel Larsen
