What is Endocarditis?

Did you know there are trillions of bacteria living in and on your body right now? Most of the time this is not a problem because the bacteria are harmless, and some even help keep us healthy. Your heart and blood vessels are usually free from bacteria, which is a good thing! That is because your cardiovascular system is supposed to stay sterile (meaning no bacteria). But sometimes injuries, even small ones like brushing your teeth too hard or scraping your knee, can let bacteria enter your bloodstream. Normally, your immune system can fight off these tiny invaders, but if it cannot, big trouble can happen fast, especially if the bacteria settle inside the heart.

Endocarditis is a serious infection that happens inside the heart (Figure 1). It usually affects the heart valves and medical devices that help the heart, like pacemakers [1]. The heart is divided into four chambers, each with a valve that acts like a door, controlling how blood flows. When bacteria infect these valves they can damage them, making it harder for the heart to pump blood effectively throughout the body. That is why it is so important to treat endocarditis quickly, before it leads to permanent damage to the heart.

Endocarditis is not very common, but some people are at a higher risk. For example, people with heart problems, such as damaged or artificial heart valves, those with special devices to help the heart, people with weakened immune systems (like older adults), or those with poor oral hygiene are more likely to develop it. What makes endocarditis tricky is that it is hard to diagnosis and treat. The bacteria involved have incredible survival skills. They can create something called a biofilm, which acts as a shield. This biofilm protects the bacteria from both your immune system and antibiotics, making the infection much harder to get rid of.

How do Bacteria Cause Endocarditis?

Endocarditis is mainly caused by three types of bacteria called Staphylococcus, Streptococcus, and Enterococcus. Among these, Staphylococcus aureus is responsible for the highest number of endocarditis cases, causing about 31% of infections [1]. This bacterium often results in more severe infections, usually requiring longer hospital stays and more complicated treatments. Surprisingly, Staphylococcus aureus normally lives harmlessly on the skin or in the noses of many people, where the immune system and beneficial bacteria keep it in check.

However, if these bacteria enter your bloodstream, such as through cuts, wounds, or dental procedures, they can travel through the body. If they reach the heart without being stopped by the immune system, they may stick to heart valves or medical devices inside the heart. Once attached, the bacteria multiply quickly, turning a few bacteria into many—possibly billions—within days. As the bacteria multiply, they start forming the protective biofilm. To build this shield, they make their own special bacterial proteins and also use human proteins from the blood, like fibrin, which normally helps form clots to stop bleeding [2]. Like a scab protecting a wound, this biofilm protects the bacteria from the immune system and antibiotics. Hidden safely within this protective shield, the bacteria continue to multiply, damaging the heart tissue and making endocarditis a serious and difficult-to-treat infection.

How Doctors Find and Treat Endocarditis

It is critical to catch endocarditis early. The sooner it is treated, the better the chance of stopping the bacteria before they damage the heart. It is important to watch for warning signs (Figure 2), but endocarditis can be hard to spot because it often looks like a less-serious illness. Early symptoms can feel like the flu, such as fever, tiredness, or shortness of breath. Sometimes, endocarditis also causes skin changes. Janeway lesions are small, painless red or purple spots that can show up on the palms of the hands or soles of the feet. Osler nodes are small, painful bumps under the skin that usually appear on the fingers or toes. These appear when clumps of bacteria or immune cells travel from the heart and get stuck in small blood vessels. Not everyone with endocarditis gets these skin signs, but they can help doctors figure out what is going on.

If something feels wrong, seeing a doctor is key because endocarditis does not go away on its own. Doctors use several tests to check for it (Figure 2). First, they listen to the heart with a stethoscope for unusual sounds like murmurs or abnormal rhythms. These abnormal rhythms are called arrhythmias, which is when the heartbeat is off, like a drummer who plays too fast, too slow, or skips a beat instead of keeping steady. If they suspect endocarditis, they will do a blood culture, where a small blood sample is placed on a special dish. If bacteria are in the blood, they will grow, helping doctors confirm the infection. Doctors also use a test called echocardiography to look at the heart. It works a bit like how bats use sound to “see”. The machine sends sound waves too high for us to hear, called ultrasound. These waves bounce off the heart and come back as echoes to create a picture. If a biofilm is found, treatment must begin right away!

The first step of treatment is giving antibiotics, bacteria-fighting medicines, through a vein in the hospital. This helps kill the bacteria. Sometimes, if the infection causes too much damage, doctors need to do surgery to repair or replace the heart valve(s) (Figure 3). Most often, the new valve comes come from an animal, like a pig or cow, or is mechanical.

Researchers are looking into new ways to outsmart bacteria [1]. They are working on faster, more accurate blood tests to diagnose endocarditis earlier. Some are developing new antibiotics, while others are testing medicines used for other illnesses to see if they can help treat endocarditis. One new approach uses ultrasound-activated microbubbles, which are tiny bubbles about the size of a red blood cell [4]. These tiny bubbles are like super-small soda bubbles, and each one has a thin skin usually made of special fat molecules called lipids, which keep the gas inside. During echocardiography, these bubbles respond to the sound waves, vibrating millions of times per second—kind of like how bubbles in a soda can jiggle and fizz when you shake it. This vibration can help break down the biofilm that bacteria use as a shield, making it easier for antibiotics and the immune system reach and kill bacteria. These new directions could help doctors find infections sooner and treat them more effectively.

Prevention: How to Protect Your Heart

Now that you know how these tiny invaders can cause trouble, let us talk about how to protect your heart from infection. One of the easiest ways? Brushing your teeth twice a day! It might sound surprising, but your mouth is full of bacteria. If your gums are unhealthy or bleed during brushing, those bacteria can slip into your bloodstream and reach your heart. Brushing and flossing every day helps keep your gums healthy and stops bacteria from getting in.

Some people’s hearts need extra protection, especially if they have had heart problems in the past. Doctors might give these people antibiotics before dental work or medical procedures. This kills any bacteria that might enter the bloodstream during the procedure. And of course, keeping your heart healthy overall is super important! Eating healthy foods, staying active, and avoiding smoking or vaping helps keep your heart strong and less likely to get infected. A strong, healthy heart is better at fighting off infections, and helps you stay healthier overall!

In conclusion, endocarditis shows us that even the tiniest invaders can cause big trouble. The heart is one of the body’s most important organs, so keeping it safe from harmful microbes is essential. From brushing your teeth to spotting symptoms early, simple actions can make a big difference. A healthy heart protects your whole body.

Glossary

Cardiovascular System: ↑ The system within the body made up of the heart and blood vessels that pumps blood throughout to deliver oxygen and nutrients and collect waste.

Endocarditis: ↑ A serious infection in the heart, mostly caused by bacteria.

Biofilm: ↑ A community of bacteria, often surrounding themselves of a self-made protective layer, allowing them to communicate and making them harder to remove.

Blood Culture: ↑ A test where doctors check your blood for harmful bacteria to figure out which medicine will work best against them.

Echocardiogram: ↑ An image created using sound waves that allows doctors to see inside your heart to check how well the heart is working and if there are any problems.

Microbubbles: ↑ Tiny gas-filled bubbles about the size of a grain of sand that doctors use in echocardiograms to help see inside the body.

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgments

This article was supported by the Hartstichting (Dutch Heart Foundation), Dekkerberus grant number 03-006-2023-0088, which provided financial support for the time and resources needed to create it. The Hartstichting supports making cardiovascular research, like this article on infections within the heart, understandable and accessible for everyone, including children

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