What are the causative agents and symptoms of pneumonia?

(N/A) Pneumonia in humans is caused by bacteria such as $Streptococcus \text{ } pneumoniae$ and $Haemophilus \text{ } influenzae$.
These bacteria infect the alveoli (air-filled sacs) of the lungs.
As a result of the infection, the alveoli get filled with fluid, leading to severe respiratory problems.
Due to the fluid accumulation in the alveoli, the diffusion of gases is impaired, and oxygen does not reach the blood capillaries effectively.
The symptoms of pneumonia include fever, chills, cough, and headache.
In severe cases, the lips and fingernails may turn gray to bluish in color.
$A$ healthy person acquires the infection by inhaling droplets/aerosols released by an infected person or by sharing glasses and utensils with an infected person.