The discovery of penicillin is attributed to Alexander Fleming in 1928. This serendipitous observation began the modern era of antibiotic discovery. Later, in the late 1940s interest in the gut microflora was stimulated by two research developments. The first was the finding that antibiotics included in animal feed promoted growth of farm animals. Second, the availability of germ-free animals provided a technique for testing the effect of the newly discovered intestinal inhabitants on the host. More recently, bacterial antimicrobial resistance has become a global concern in the medical and agricultural fields. Antibiotic-resistant strains of bacteria are an increasing threat to animal and human health, with resistance mechanisms having been identified and described for all known antimicrobials currently available for clinical use.

At this time, there is an increased public and scientific interest regarding the administration of therapeutic and subtherapeutic antimicrobials to animals, due primarily, to the emergence and dissemination of multiple antibiotic-resistant zoonotic bacterial pathogens. Social pressures have led to the creation of regulations to restrict antibiotic use in poultry and livestock production. There is a necessity to evaluate potential antibiotic alternatives to improve disease resistance in a highly intense food animal production system. Nutritional approaches to counteract the debilitating effects of stress, infection and chronic inflammation, may offer useful alternatives to antibiotics. Improvement of disease resistance of animals grown without antibiotics has been shown not only beneficial for the animals’ health, welfare, and production efficiency, but also as a key strategy to improve the microbiological safety of animal products. Recent international legislations and increasing consumer demands to withdraw growth-promoting antibiotics and limit the therapeutic use of available antimicrobials, have resulted in the reseach and development of alternative feed additives such as; probiotics prebiotics, synbiotics, phytochemicals, enzymes, organic acids, and bacteriocins for treatment of bacterial infections. Metchnikoff founded the research field of probiotics aimed at modulating the intestinal microflora. However, other parts of the body containing endogenous microorganisms or problems relating to the immune system may also be candidates for probiotic therapy. Nowadays, research is still heavily biased toward gastrointestinal applications for probiotics, but the possibilities for affecting many areas of health and/or animal production are numerous.

The objectives of this research topic are to highlight promising research results and novel technologies that could potentially lead to alternatives to conventional antibiotics, assess challenges associated with their commercialization, and provide actionable strategies to support development of alternative antimicrobials. It is also dedicated to becoming a forum on the latest scientific breakthroughs and technologies that could provide new options for preventing and treating diseases. These new technologies may have direct applications as medical interventions for humans and animals. Some of them may include natural alternatives to antibiotics, immune modulation approaches, gut inflammation models, gut microbiome analysis and their relationship with health and disease as well as regulatory pathways to enable the licensure of alternatives to antibiotics additives.

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