Humans are complex multicellular organisms, but we are not alone. Our body provides various habitats to trillions of bacteria. Scientists estimate that humans carry 10 times more bacteria than the number of the cells you are made of. The PBS video The Invisible Universe introduces the concept of microbiome and explains why we need bacteria to be healthy (click here Word Document for a transcript of this video). However, do not be fooled by these friendly bacteria as many have the potential to make you sick. Read the article Stop the Spread of Superbugs: Help Fight Drug-Resistant Bacteria and explain:

• Why antibiotics target bacteria but not human cells.
• How the misuse or excess of antibiotics are responsible for the emergence of "superbugs" like MSRA.