*2.5.2 Potential roles of the pharyngeal microbiome*

Animals have developed strategies that allow them to evade the invasion of microbial pathogens and humans are no exception. Therefore, the one inhabited by commensal microorganisms that participate as defenders has a fundamental action to comply with these strategies. However, the role of the pharyngeal microbiome in respiratory tract infections (RTIs) is not fully understood, there is evidence to suggest a protective effect, like the gut microbiome [89].

*Factors of Nasopharynx that Favor the Colonization and Persistence of* Staphylococcus aureus *DOI: http://dx.doi.org/10.5772/intechopen.95843*

The pharynx microbiome plays a crucial role in lining the mucosa of the respiratory tract by protecting against infections by airborne pathogens, in addition to the immune mechanisms of the host, particularly against emerging infectious agents [89, 91].

Homeostasis of the pharyngeal microbiome is necessary to prevent infections caused by native bacterial species, which allows the abundant development of each species. Many pathogenic species can adapt well to the pharyngeal ecosystem and become established in the resident microbiome, rendering the host asymptomatic (such as *S. aureus*, *H. influenza*, and *Mycoplasma pneumoniae*) [92]. In epidemiological studies it has been suggested that the proportion of resident pathogens varies seasonally, as does the incidence of RTIs attributed to them [93].
