Gut Microbiome and Its Role in Enteric Infections with Microbial Pathogens

Abstract

In this chapter, we will discuss enteric bacteria and the ways the body works to prevent these bacteria from infecting the host and causing disease. Pathogens can enter the body through contaminated food or water but, in order to colonize within the body, must contend with natural barriers and defenses within the host organism. These defenses can include physical barriers such as mucosa or chemical barriers such as a change in pH. Biological defenses also exist in the form of immune cells and the gut microbiome. The bacterial composition of the gut microbiome plays an important role in preventing a pathogen from being able to colonize and multiply within the gut. Having a diverse and healthy community of bacteria also provides functions for the host organism that its body processes cannot achieve naturally. While not all bacteria are beneficial to the host, it is still important to have a balance within the gut at all times. The use of antibiotics can alter this balance, but the exact effect that antibiotics has on the microbiome is not fully understood at this time. Many factors can affect the gut microbiome and the diversity and abundance of the bacteria found there. These include age, diet, lifestyle, geography, and genetics. Understanding how and why these factors affect the gut microbiome has allowed us to better understand the important role bacteria play in the overall health of an individual. An individual who is chronically ill or unhealthy will have a gut microbiome that is less diverse and balanced. Whether this is a result of the illness or a contributing factor to the illness still shows the relationship that exists between the host and the community of bacteria. Competition between the various types of bacteria within the gut has also been shown to be to the benefit of the host. Resident “good” bacteria within the gut can prevent an infection by preventing a pathogen from physically attaching to the lumen or preventing it from receiving nutrients. Another defense against a possible pathogenic infection is the introduction of beneficial bacteria into the gut through probiotics. Probiotic use has been increasing over the years, and the benefits have been studied extensively. Probiotics can help the body by preventing colonization and regulating the immune response to pathogenic versus nonpathogenic bacteria. Besides probiotics, other biotherapeutic methods are being developed using microbes and focusing on the interaction of the entire body with the gut microbiome. Research focused on more understood bacteria such as E. coli and Lactobacillus has aided in expanding the knowledge of other species and even other organisms such as fungi. The number of bacteria and small microorganisms is vast, and it is starting to become clear that utilizing these organisms for medicinal and preventive purposes can be beneficial to overall human health.