Final answer:
The predominant normal flora of the upper respiratory tract include species like Staphylococcus epidermidis, viridans group streptococci (VGS), Corynebacterium spp., Propionibacterium spp., and Haemophilus spp. The oropharynx also contains species like Prevotella, Fusobacterium, Moraxella, Eikenella, and Candida fungal isolates. The lower respiratory tract is sparsely populated with bacteria, including species of Pseudomonas, Streptococcus, Prevotella, Fusobacterium, and Veillonella.
Step-by-step explanation:
In the upper respiratory tract, the predominant normal flora include Staphylococcus epidermidis, viridans group streptococci (VGS), Corynebacterium spp. (diphtheroids), Propionibacterium spp., and Haemophilus spp. In the oropharynx, in addition to the bacteria found in the nasal passages and sinuses, there are also species of Prevotella, Fusobacterium, Moraxella, and Eikenella, as well as some Candida fungal isolates.
In the lower respiratory tract, the most common bacteria identified include species of Pseudomonas, Streptococcus, Prevotella, Fusobacterium, and Veillonella. However, it is not clear if these small populations of bacteria constitute a normal microbiota or if they are transients.