Question

Which statement regarding normal microbiota of the human respiratory system is FALSE?

a) The trachea normally may contain a few bacteria.
b) The upper respiratory tract is mostly sterile.
c) The ciliary escalator in the bronchial tubes keeps the lower respiratory tract nearly sterile.
d) Potentially pathogenic microorganisms are present in nonsterile portions of the respiratory tract but usually do not cause disease.

Answer 1

The statement that the upper respiratory tract is mostly sterile is false. The upper respiratory tract does harbor normal microbiota, although the density and diversity of the microbiota are lower than in the mouth and throat.