Q.Which of the following is/are responsible for pneumonia in humans?

Pneumonia is an inflammation of lung tissue, most often caused (in its bacterial form) by Streptococcus pneumoniae, though viral and fungal pneumonias also occur. The bacteria infect the alveoli — the tiny air sacs where oxygen and carbon dioxide are exchanged — causing them to fill with inflammatory fluid and pus, which severely impairs normal gas exchange.

Symptoms. Typical features include high fever with chills, a productive cough bringing up mucus or phlegm, chest pain (often worse on breathing), and difficulty breathing; in severe, oxygen-starved cases, the lips and fingernails may take on a bluish tinge (cyanosis).

Prophylaxis. Prevention emphasises maintaining good general nutrition and immunity, avoiding overcrowded and poorly ventilated living spaces (which favour droplet transmission), and vaccination against S. pneumoniae, particularly recommended for high-risk groups such as young children and elderly people whose immune defences are weaker.

Exam-focused takeaway: the key facts to retain are the causative bacterium (Streptococcus pneumoniae), that it specifically affects the alveoli (impairing gas exchange, unlike the upper-respiratory-tract common cold), and the twin preventive strategies of reducing overcrowding and vaccinating vulnerable groups. …