What type of bacteria is responsible for causing tetanus?

The correct choice is bacilli because tetanus is caused by the bacterium Clostridium tetani, which is a rod-shaped bacterium that falls under the category of bacilli. Bacilli are characterized by their elongated, cylindrical shape, and this specific structure allows them to thrive in anaerobic environments, such as wounds where there is little to no oxygen.

In the case of tetanus, when Clostridium tetani spores enter the body through breaks in the skin, they can produce a potent toxin that affects the nervous system, leading to muscle stiffness and spasms characteristic of the disease. The bacilli's ability to form spores enhances its survival in harsh conditions and contributes to the risk of tetanus infections.

Other types of bacteria, such as cocci, spirilla, and vibrio, have different shapes and characteristics. Cocci are spherical, spirilla are spiral-shaped, and vibrio are comma-shaped. While these bacteria can also cause various infections, they are not responsible for tetanus, which specifically connects to the bacilli form of bacteria.