Gut bacteria boosts immune function among newborns and defends against infections, study finds

A recent study found that a type of intestinal bacteria not only aids digestion in infants, but also shows potential in defending young patients from a host of bacterial infections. According to the World Health Organization (WHO), bacterial infection remains to be a major contributor to neonatal deaths worldwide. Bacterial infections, such as sepsis, pneumonia, tetanus and diarrhea, accounts for 36 percent of deaths among infants around the world, WHO data shows. However, the recent study revealed that a certain type of  intestinal bacteria known as Clostridia contained protective properties against a host of harmful bacteria.

To carry out the study, a team of researchers from the University of Michigan Medical School examined both newborn and adult germ-free mice. Adult mice showed a more diverse gut microbiome including Clostridia and Bacteriodes bacteria. The newborn mice did not have the bacteria, and primarily got their nutrition from their mother’s milk. This made the animal models more susceptible to harmful bacteria similar to human pathogens. This also made them an ideal test specimen to assess the effects of various microbes in the body.

The research team then took fecal samples from four-day-old, 12-day-old, and 16-day-old normal mice. The experts transplanted the bacteria from the fecal samples to the germ-free mice and exposed them to a strain of Salmonella that infected the intestines but not the whole body. The research team found that 50 percent of germ-free mice died after receiving bacterial samples from four-day-old normal mice. However, none of the animal models died after receiving samples from 16-day-old normal mice.

The scientists replicated this by exposing germ-free mice to Citrobacter rodentium. The research team found that a large number of germ-free mice died after being transplanted with bacteria from four-day-old samples. However, C. rodentium levels dropped in those that received the 16-day-old samples. In addition, the researchers found that germ-free mice that received the Clostridia bacteria were able to resist infections. According to the experts, 90 percent of Clostridia recipients remained alive at one week following Salmonella exposure, compared with only 50 percent in those that did not receive the bacteria. Furthermore, germ-free mice with impaired immune system that were given gut microbes from four-day-old samples were able to resist Salmonella infection. However, they only able to do so if they received extra doses of Clostridium first. Mice transplanted with Clostridium were also able to resist C. rodentium infection, the researchers added.

“Any parent knows that newborns are very susceptible to infections in the first year of life, including enteric, or gut, infections. This work suggests that the lack of protective bacteria in the gut microbiota is a mechanism for that susceptibility, perhaps more than the age of the immune system,” said senior author Dr. Gabriel Nunez in

The findings were published in the journal Science.

Potential implications in infant infections

The recent findings may show potential in the treatment of various health hazards such as Salmonella, E.coli, and C. difficile infections. According to, about 50,000 cases of Salmonella infections are reported in the U.S. annually, with about a third of cases involving children four years old or younger. Salmonella symptoms include fever, cramps and diarrhea. The infection may cause other serious conditions such as  meningitis and pneumonia. (Related: 10 simple ways to prevent salmonella and other bacteria).

According to the American Academy of Pediatrics, C. difficile infection has shown a steady increase since 1997. The infection, typically acquired from the environment or through fecal-oral route, is touted to be the most common cause of  antimicrobial-associated diarrhea. On the other hand, E.coli can be acquired through contaminated food, water or from other infected people or animals. The infection is associated with severe forms diarrhea, extreme fatigue, and even seizures.

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