How Can Chicken Gut Microbiomes Affect Human Health?
The human microbiomes plays important roles in our health, which scientists are beginning to unravel —and it turns out that the microbiomes of other animals also play important roles in human health. A new Infection and Immunity study reports that the microbiomes of chickens can influence whether those chickens are colonized by the bacterium Campylobacter jejuni, one of the most common causes of diarrheal diseases in people. While a growing consensus of scientists agree that animal, environmental, and human health are all interrelated (a concept best known as One Health), studies such as this one help demonstrate how the health of one species can affect that of another.
First author Zifeng Han and senior scientist Silke Rautenschlein raised chickens in one of two experiments. In the first, some chickens were raised on a feed diet without antibiotics; some were raised on a feed diet that contained an antibiotic cocktail. In the second, animals raised in specific pathogen-free (SPF) conditions were compared to those raised in germ-free conditions, meaning they compared chickens with a microbiome containing no known pathogens to chickens lacking all commensal microbial flora. By testing the fecal droppings with 16S rRNA gene sequencing, the researchers determined that antibiotic-treated and -untreated birds had similar numbers and overall diversity of their gut bacteria, but that the dominant bacterial types differed between the two groups. Germ-free birds were confirmed to have no bacteria, fungi, or yeasts in their droppings.
When exposed to C. jejuni, antibiotic-treated birds were colonized with nearly 10-fold more bacteria than were colonized in birds not treated with antibiotics (see below, panel A). Colonization differences were more extreme between the SPF and the germ-free birds (below, panel B). The authors further demonstrated that the immune response to C. jejuni colonization differed between untreated and antibiotic-treated, and between SPF and germ-free chicken groups, suggesting microbes may play a protective role during C. jejuni colonization.
Gut microbiota were previously shown to influence C. jejuni colonization in mice, and the Infection and Immunity study significantly expands on those reports to show that the same phenomenon occurs in chickens. Chickens and other poultry are the major reservoir of Campylobacter, which can pass to people through contaminated animal products, making this study extremely relevant to human health as well as animal health (chickens with C. jejuni can suffer gastrointestinal distress and diarrhea similar to that in people). Future studies may find probiotic or prebiotics administered to chickens can help decrease bird colonization levels, decreasing the 1.3 million annual Campylobacter cases estimated in the United States.