Anja Pastor: Good morning Christine, thank you so much for being with us today and for giving us the opportunity to talk about a fascinating topic – namely bacterial translocation. So let’s dive directly into the topic – what is bacterial translocation?
Christine N. Vuong: Bacterial translocation is the inappropriate colonization of bacteria from the gut into other parts of the body. The microbiota of the gut, even the beneficial microbes used for digestion, can cause health issues and diseases when outside of the gut environment. Bacterial translocation occurs after damage to the gastrointestinal wall or barrier. In a healthy animal, the intestinal wall selects which nutrients and cells can move between the open lumen of the gastrointestinal tract and into the systemic systems of the body.
When damage occurs to this barrier function, bacteria (and other microbes) from the gut environment are able to enter the body system and colonize in other organs. This damaged and impaired gut barrier function is commonly known as “leaky gut” syndrome. Several kinds of stressors can cause damage to the gut barrier to favor bacterial translocation conditions. Feeds with too high indigestible fiber, feed which causes highly viscous gut digesta, environmental stressors (high ammonia levels, poor litter quality, heat/cold stress), or disease incidences (both metabolic and infectious) can induce various levels of leaky gut.
AP: When are birds most susceptible to bacterial translocation?
CV: Once placed, a major stressor in birds occurs at 2–3 weeks of age, when maternal immunity in the chicks declines. This is when the birds are bombarded by multiple infectious diseases and must mount an appropriate immune response to all of these pathogens; thus, we typically observe flushing at this age. This holds true in other species, particularly at weaning. In longer-lived breeders and laying hens, highly intensive production can cause systemic stress on the body and cause the birds to be more susceptible to leaky gut and bacterial translocation
AP: And how does intestinal inflammation favor bacterial translocation?
CV: Inflammation is very energy demanding and is typically beneficial when the immune system is properly functioning and using inflammation as a short duration response to prevent illness or infection. But inflammation can also be damaging, especially in situations of chronic inflammation. Too much inflammation damages the tight junctions between the epithelial cells, leading to impaired gut barrier function/bacterial translocation. Unfortunately, this can create a feedback loop in which the initial damage to the gut barrier permits bacterial translocation to occur, and the resulting unwanted bacterial colonization in other peripheral organs induces more inflammation. This dysfunction can negatively alter the microbiome, impair the immune system’s ability to function properly, and results in an unhealthy and less productive chicken.
AP: Based on your experience – how relevant is bacterial translocation for poultry production? Can you estimate how many birds/flocks are affected by bacterial translocation?
CV: All animals have some level of stress that can cause fluctuations in inflammation throughout the body. Poultry are also subjected to these stresses, particularly as they are raised at higher density and have the highest physiological growth and production demands on the body in the shortest amount of time. The exact amount of birds affected by bacterial translocation is unknown and difficult to estimate as there are also different levels of gut inflammation.
AP: How come that some farms are more affected by bacterial translocation in their birds than others?
CV: Environmental factors and management play an important role in controlling bacterial translocation at the farm level. Rearing conditions (diet, temperature, litter quality, air quality, water quality, and feed quality) can induce low levels of inflammation in the gut, predisposing the gut to bacterial translocation. Multiple concurrent stressors can exacerbate inflammation. The infectious diseases endemic to the area also affect the birds’ health conditions. Management of these diseases (either by vaccination or biosecurity) can greatly reduce pathogen-induced leaky gut.
Specific bird lines can also be genetically resistant or susceptible to different environmental stressors and diseases. Based on the breed or line used at a particular facility, the interaction between genetics and the external factors results in variable levels of gut inflammation for each farm.
AP: Is bacterial translocation just relevant for chickens for fattening or also for layers? What about other livestock?
CV: The physiological stress of both rapid muscle growth and egg production can cause infl ammation throughout the body, including the gastrointestinal tract. This is also true for other agricultural animals going through growth or high production phases. Beyond physiological stress, all animals are infl uenced by the environment in which they are reared and the resulting infl ammation associated with that environment, even humans.
AP: How can the negative impact of bacterial translocation be alleviated on farm level?
CV: Good nutrition, maintaining a healthy environment, and preventing disease can greatly alleviate infl ammation and incidences of bacterial translocation. Diff erent feed components can alter the gut environment, some feeds causing more intestinal infl ammation than others (e.g., non-starch polysaccharides). Because these feed components can induce an unhealthy gut, they can also indirectly allow the colonization of pathogenic bacteria. Understanding your feed and how that formulation can infl uence health (not just growth or production parameters) is very important to controlling and alleviating bacterial translocation.
AP: How can the bacterial translocation be assessed on farm level and under academia conditions? Is there a way to do it in a non-invasive way?
CV: Accurate bacterial translocation is measured by collecting organs for subsequent bacterial culture to confi rm colonization of bacteria outside of the gut. This process does involve euthanizing birds for organ collection and having the equipment to sterilely collect organs for culture, which is diffi cult to achieve in a farm setting.
There are methods to measure overall infl ammation and indirect measurements for leaky gut utilizing serum, gut tissue, or non-invasive fecal samples (infl ammatory markers, serum FITC-d, tight junction proteins, or calprotectin), but these methods still require laboratory equipment (qPCR, RNAseq, or plate reader equipment).A baseline level of normal/healthy also has to be established for comparison (this baseline level diff ers based on breed and rearing conditions). These assay requirements are suitable for research conditions to evaluate diff erent treatments, but makes farm-level assessment of gut inflammation/bacterial translocation fairly diffi cult.
AP: What is your Take Home Message for academia and the livestock industry regarding bacterial translocation?
CV: Bacterial translocation is multifactorial, but the best way to control bacterial translocation is through good management (controlling the environment, the feed quality and formulations, as well as the disease prevention programs). All of these elements go hand in hand with quality management.
AP: Thank you for the interview, Christine!
Expert Christine N. Vuong
Ph.D., Research scientist, University of Arkansas, USA
Christine N. Vuong is a Research Scientist at the University of Arkansas Poultry Health Laboratory, specializing in infectious diseases. She obtained her Ph.D. in immunology at Texas A&M University, USA, before she completed her post-doctoral fellowship in vaccine development in the Poultry Science department at the University of Arkansas.
So far, Christine contributed to more than 30 peer-reviewed publications and supports science journals such as Nature, Poultry Science, or the Annual PSA Conference as reviewer.
Christine is a supervisor of various research projects related to pathogen eff ects on intestinal barrier integrity as well as completing research on development of vaccines/immunoassays to improve animal welfare and gut health.
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