What is tetanus caused by?

• A. A virus transmitted by air
• B. A bacterium that grows in oxygen
• C. A bacterium that grows in the absence of oxygen
• D. A fungi found in dirty environments

Answer: (C)

Tetanus is caused by a bacterium known as Clostridium tetani, which thrives in anaerobic conditions, meaning it grows in environments that are low in oxygen. This is why the correct answer centers on a bacterium that grows in the absence of oxygen. The spores of C. tetani are often found in soil, dust, and animal feces. When the bacterium enters the body through wounds or deep punctures (especially in environments where oxygen is lacking), it can produce a potent toxin that affects the nervous system, leading to the symptoms commonly associated with tetanus, such as muscle stiffness and spasms.

A virus transmitted by air is not responsible for tetanus, as it specifically requires a bacterial source. Similarly, while oxygen is crucial for many types of bacteria, C. tetani is anaerobic and thus grows in environments devoid of oxygen, reinforcing why this particular answer is accurate. Fungi, while they can be found in dirty environments, do not cause tetanus and are a different category of microorganisms altogether.