Alex Ehsan, MD, PhD · Medical search

Bacterial Infections

Educational information. Individual clinical review of this presentation by Dr. Ehsan is not yet documented. It does not replace personal medical evaluation.

Source: MedlinePlus, National Library of Medicine. Read the original source

MedlinePlus data edition September 26, 2026. Imported September 27, 2026. These dates do not indicate a new clinical review of the article.

What are bacteria?

Bacteria are tiny organisms (living things) that have only one cell. Under a microscope, they look like balls, rods, or spirals. They can be found almost everywhere on Earth. There are lots of bacteria in and on your body. In fact, your body has about 10 times more bacteria cells than human cells.

There are many different types of bacteria. Most types don't make you sick. Some types are helpful. For example, "good" bacteria in your digestive system can help your body digest food and absorb vitamins and minerals. They can help protect you from getting sick. Bacteria are also used in making foods like yogurt and cheese.

But some types of bacteria can cause an infection and make you sick. They are called infectious bacteria. These bacteria can reproduce quickly in your body. Many of them give off toxins (poisons) that can damage your cells and make you sick. Other types can move into and damage your tissues. A few examples of bacteria that cause infections include Streptococcus, Staphylococcus, and E. coli.

How do bacterial infections spread?

There are different ways that bacterial infections may spread:

What are the treatments for bacterial infections?

Sometimes your immune system may be able to fight off a bacterial infection. But when you do need treatment, it will be with antibiotics.

When you take antibiotics, follow the directions carefully. Each time you take them, there is a risk that the bacteria will become resistant to the effects of the antibiotics. This is called antibiotic resistance. When this happens, the bacteria are not killed, and they continue to grow. They can cause resistant infections, which can be difficult, and sometimes impossible, to treat.

Can bacterial infections be prevented?

You can help prevent some bacterial infections by:

Questions for your care team

General prompts to help prepare for your appointment.

For a life-threatening emergency, call 911 in the U.S. or your local emergency number.

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