Final answer:
Common bacteria in the upper respiratory tract include Firmicutes, Actinobacteria, Proteobacteria, Staphylococcus epidermidis, viridans group streptococci, Corynebacterium spp., Propionibacterium spp., Haemophilus spp., and others.
Step-by-step explanation:
The types of bacteria that are common in the upper respiratory tract include a diverse microbiota. The nasal passages and sinuses are usually colonized by Firmicutes, Actinobacteria, and Proteobacteria. Some of the most common bacteria identified are Staphylococcus epidermidis, viridans group streptococci (VGS), Corynebacterium spp. (diphtheroids), Propionibacterium spp., and Haemophilus spp. In the oropharynx, these are accompanied by additional bacteria such as species of Prevotella, Fusobacterium, Moraxella, and Eikenella, along with some Candida fungal isolates. A portion of the population also carries Staphylococcus aureus asymptomatically in their nostrils.
Furthermore, the pharynx can harbor pathogenic strains of Streptococcus, Haemophilus, and Neisseria. It's important to note that many members of the normal microbiota are opportunistic pathogens and can cause infections if they overcome the body's immune defenses.