Steven Holland on how bacteria make us sick

Titus, a 6-year-old student from the International School of Tiajin in China, asks the scientists about the bacteria that make us sick.

Titus Goh: What are the bacteria that attack our nose and ears? How do they make us sick?

Earthsky asked Dr. Steven Holland, a chief scientist at the National Institute of Allergy and Infectious Diseases at the NIH. He told us that bacteria are all around us, and only sometimes do they make us sick.

Steven Holland: Bacteria are very small life forms that can grow and divide. Most bacteria could not care less about us. There are millions of them in the water, in the soil, and the air.

But, he said, there are certain types of bacteria that can get inside our bodies and cause sicknesses like sinus infections, strep throat, and ear infections.

Steven Holland: Infections are really what happens when bacteria steps over a line and our body says stop. When our body says stop, it usually turns on what are called white blood cells – cells which fight against infection.

Dr. Holland said it’s these white blood cells fighting the bacteria that makes you feel sick.

Steven Holland: Swelling, pain, warmth, and tenderness are very, very common signs of infection. Those tell you your body thinks there is a problem, and that problem is often one due to a bacteria.

According to Dr. Holland, we usually don’t get sick from the bacteria we’re exposed to, because our bodies have a built-in defense system.

Steven Holland: Bacteria inhabit our noses and ears and throats and lungs, but they don’t usually stay there very long. There are small hairs inside the lungs beating in a certain direction, like small racquets, that are moving mucus away, so we bring it up and spit it out. One of the reasons we do so well with bacteria is because we’re very good at getting rid of them.

Dr. Holland said that we are both born with, and acquire, immunity from certain bacteria. That means our bodies have developed new ways of fighting off, or resisting, the bacteria that get inside us.

Steven Holland: Each person’s body has to develop a way to fight them. Those are called antibodies; little proteins that recognize bacteria, and then bind to them and help them get destroyed. That’s what vaccines that children get are for, to help you build those antibodies to help you avoid getting sick.

He said a big question is why, if our bodies are so good at avoiding most bacterial infections, certain bacteria can still make us sick. He said even though bacteria is so common, there is still much that scientists don’t know about how it interacts with our bodies.

Steven Holland: Why is it that some bacteria cause infections and others don’t? Why is it that people can walk around and carry bacteria in their nose or throat or ears for years, and then one day cause a problem, whereas all the days before that, it didn’t cause a problem? And trying to figure out why it is that things change is very, very important. Because then we can understand which bacteria really pose a problem, or what it is that happens to bacteria that really pose a problem.

Our thanks today to the Monsanto Fund, bridging the gap between people and their resources.