Which type of catheter cannot be steam sterilized?

Rubber catheters cannot be steam sterilized due to the material properties of rubber. Rubber is sensitive to heat and moisture; exposure to steam sterilization can cause it to break down or lose its functional integrity. This leads to concerns about the efficacy and reliability of the catheter after such a sterilization process.

In contrast, plastic, silicone, and metal catheters can typically withstand the conditions of steam sterilization, making them suitable options for medical use where sterility is crucial. Plastic and silicone have good heat stability and are designed to handle the temperature and moisture levels involved in steam sterilization safely. Metal catheters, made from materials like stainless steel, are also highly resistant to the effects of heat and moisture, allowing for effective sterilization without compromising the material.

Therefore, the inability of rubber catheters to endure steam sterilization without degradation clearly identifies them as the correct answer in this question.