Question

The most common etiologic agent of lower respiratory tract infection among adults younger than 30 years of age is:

A) Haemophilus influenzae
B) Streptococcus pneumoniae
C) Mycoplasma pneumoniae
D) Chlamydia pneumoniae

Answer 1

The most common etiologic agent of lower respiratory tract infection among adults younger than 30 years of age is Streptococcus pneumoniae.

Step-by-step explanation:

The most common etiologic agent of lower respiratory tract infection among adults younger than 30 years of age is Streptococcus pneumoniae. This bacterium is a gram-positive, alpha hemolytic streptococcus that is commonly found as part of the normal microbiota of the human respiratory tract. It typically appears as pairs and initially colonizes the bronchioles of the lungs before spreading to the alveoli. The infection causes inflammation and the alveoli to fill with exudate, resulting in symptoms such as a productive cough with bloody sputum.