Which disease is caused by a bacterium and forms a grey membrane in the throat that can block the airway?

• A. Diphtheria
• B. Whooping cough
• C. Tuberculosis
• D. Strep throat

Answer: (A)

Diphtheria is caused by the bacterium Corynebacterium diphtheriae, which is responsible for the formation of a thick, grayish membrane in the throat. This membrane is a characteristic feature of the infection and can lead to significant airway obstruction, posing a serious risk to breathing. The presence of the membrane is due to the local effects of the bacteria, which produce toxins that damage the epithelial cells in the throat. This damage not only triggers inflammation but also facilitates the creation of a pseudomembrane made up of dead cells, bacteria, and immune cells, which can obstruct the airway if it becomes large enough.

In contrast, whooping cough, caused by Bordetella pertussis, primarily leads to severe coughing fits but does not create a membrane that blocks the airway. Tuberculosis, caused by Mycobacterium tuberculosis, affects the lungs but does not typically present with a membrane formation in the throat. Strep throat, which is an infection from Streptococcus bacteria, can cause a sore throat and swelling but does not lead to a gray membrane formation as seen in diphtheria. Thus, diphtheria is uniquely characterized by its membrane and airway obstruction.