Sample bottles provided by a certified laboratory for bacteriological sample collection are:

Sample bottles provided by a certified laboratory for bacteriological sample collection are ready to use. This means that they are pre-sterilized and designed specifically for collecting samples without requiring any additional preparation by the user. This is critical in microbiological studies, as contamination can compromise results. Ensuring that the bottles are sterile when they are filled helps to achieve accurate and reliable test outcomes.

The reasoning behind the other options highlights their impracticality or inappropriateness. Reusable bottles could introduce the risk of contamination since they would require cleaning and sterilization to eliminate any residual microbes. Easily disposable bottles might not emphasize the necessity for sterility in the sampling process, and bottles that require washing before use pose a significant risk of not being properly sterilized, potentially leading to inaccurate bacteriological results. Therefore, having ready-to-use bottles streamlines the sampling process and aligns with best practices in microbiological testing.