Dr. Margie Lee works at the Virginia-Maryland College of Veterinary Medicine, undertaking several roles including being the interim director of the Animal Cancer Care and Research Center. Lee has uncovered the secrets of the chicken’s microbiome. Consequently, this has changed the way the poultry industry tackles Salmonella.
The research has advanced our understanding of the ways that competing bacteria in chicken intestines fight against Salmonella. The findings carry implications not only for combatting Salmonella bacteria in chicken populations but potentially for increasing understanding of the human gut biome.
U.S. chicken – 4% infection rate
Salmonella bacteria (salmonellosis) are the primary cause of foodborne illness worldwide. As a relevant example, eating undercooked, contaminated chicken is a major cause of illness. In the U.S., according to Centers of Disease Control, one out of every 25 packages of chicken is contaminated with Salmonella.
Antibiotics have proven to be subpar in ridding chickens of Salmonella. To safeguard chickens and to protect public health over the longer-term, the poultry industry needs to eliminate the bacteria from its flocks.
According to Lee, the solution lies in a diverse, flourishing community that just so happens to exist between a chicken’s small and large intestine: the gut microbiome.
Chicken probiotics
Lee has identified how day-of-hatch chicks with a high bacterial load of Salmonella often died, yet chicks that were at least a day old always lived, even with enough Salmonella in their systems to make a human ill.
This means that something happens over the course of a single day in a chick’s life that stops Salmonella from overwhelming the chicken’s immune system. This factor is termed ‘competitive exclusion’.
Competitive exclusion is a process in which other bacteria exclude pathogens from taking hold in the intestines. These competitive exclusion products are derived from the poop of adult, Salmonella-free chickens. When chicks come into contact with these products, beneficial bacteria enter their bodies, and the chicks go on to develop a more robust gut microbiome.
With the first stage of the research, Lee looked at how Salmonella organisms responded to Aviguard, a commercially available competitive exclusion product, versus a microbial community from chicken cecum (a pouch that forms the first part of the large intestine) that contained Salmonella.
Secondly, Lee examined the response of the cecal communities to Salmonella in birds with high and low amounts of Salmonella colonization. To do this, Lee’s team created a “reporter strain” using fluorescence to monitor salmonella growth and to track SPI-1, which codes for a protein secretion responsible for virulence.
Lee found that the chicken’s microbiome engages in a combination of competition — as in competing for limited resources — with attenuation, or weakening Salmonella’s virulence, and antagonism, or generating antimicrobials to fight Salmonella. Here antagonism was the primary contributor — the organisms within the gut produce their own antibiotics to combat Salmonella bacteria.
This may offer clues for developing effective probiotics. The research appears in the journal Frontiers in Microbiology, titled “Peeling back the many layers of competitive exclusion.”
