Look at the picture. What is likely to have killed the less resistant strains of bacteria?

To provide a clear answer, I would need some specific information from the image you're referring to, such as the context or factors affecting the bacteria. Generally, factors that can kill less resistant strains of bacteria include:

1. Antibiotics: Certain antibiotics target specific bacterial functions or structures.
2. Environmental Conditions: Changes in temperature, pH, or the presence of disinfectants can affect bacterial survival.
3. Host Immune Response: The immune system can eliminate weaker bacterial strains.

If you can describe the contents of the image or provide more details, I could give a more tailored response.