Less than 1 percent of bacteria cause harm to the body They can invade the body through a cut or wound or enter in another way As these bacteria grow and multiply they release toxins or poisons that infect and break down human body cells This causes illness or infection Some bacteria have flagella that help them move around flagella 6
Coughing helps the body get rid of harmful substances in the lungs Common infections caused by bacteria include acne and strep throat To treat an infection caused by bacteria a doctor might prescribe antibiotics Antibiotics fight and kill infection-causing bacteria DID YOU KNOW Sometimes antibiotics can cause problems Overuse and incorrect use of antibiotics can actually encourage resistant bacteria to grow Not finishing all the prescribed antibiotics kills only the weak bacteria The stronger bacteria might still survive They can multiply and pass their resistance to other bacteria That is why it is important to take all the antibiotics a doctor prescribes 7
DID YOU KNOW Helpful bacteria produce foods such as yogurt sour cream sauerkraut and vinegar The holes in Swiss cheese come from bacteria Probiotics or disease preventing bacteria help stop diarrhea and slow infections Probiotics can be found in yogurt and some types of juice Antibiotics work by selecting bacteria cells that are in the body and destroying them 8
cell virus Virus Reproduction reproduced viruses virus genetic material reproducing viruses Viruses are much smaller than bacteria They need a host to exist A host is an organism such as a plant animal or person off which another living thing lives A virus invades a living cell and overtakes it The virus then makes the cell produce more of the virus These new viruses invade and damage other cells in the body Viruses can even attack bacteria Chicken pox and the flu are common infections caused by viruses Antibiotics do not kill viruses But some antiviral drugs slow virus reproduction They can ease symptoms and shorten the illness 9
