Staphylococcal infection is caused by a common group of bacteria that usually live harmlessly on the skin or in the nose of many healthy people, but can sometimes enter the body through cuts or wounds and cause problems ranging from minor skin irritations to life-threatening conditions affecting the blood, bones, lungs, or heart.
Understanding Staphylococcal Infections
Staphylococcal infections are illnesses caused by bacteria called Staphylococcus, often simply called “staph.” There are more than 30 different types of these bacteria, but the most common one that causes problems in humans is called Staphylococcus aureus. This particular type is responsible for most staph infections people experience.[1][2]
What makes staph bacteria interesting is that they are very common. About 30% of people carry these bacteria on their skin or inside their nose without ever getting sick. Most of the time, the bacteria just sit there doing nothing harmful. This situation is called being “colonized” with staph. People who carry staph bacteria but have no symptoms are known as carriers, and they can pass the bacteria to others.[4][12]
The bacteria become a problem when they manage to get inside the body. This usually happens through a break in the skin, such as a cut, scrape, surgical wound, or even a small pimple. Once inside, the bacteria can multiply and cause an infection. Sometimes these infections are mild and affect only the skin. Other times, they can spread deeper into the body and become very serious.[3]
How Common Are These Infections?
Staphylococcal infections are extremely common in the United States and around the world. Millions of skin staph infections occur in the United States every year. Most of these are mild and can be treated successfully with antibiotics. However, when staph bacteria get deeper into the body, they create many thousands of serious cases annually, some of which can be deadly.[2]
Even though many people carry staph bacteria without problems, the risk of actually developing an infection exists for everyone. Children, adults, and elderly people can all get staph infections. The bacteria are found everywhere in our environment—on doorknobs, gym equipment, towels, clothing, and many other surfaces that people touch every day.[3]
Healthcare settings like hospitals see a significant number of staph infections. In fact, staph bacteria are one of the most common causes of infections that people acquire while staying in hospitals. These hospital-acquired infections, also called nosocomial infections, can be particularly dangerous because they often involve strains of bacteria that are resistant to commonly used antibiotics.[6]
What Causes Staphylococcal Infections?
The root cause of a staphylococcal infection is always the entry of staph bacteria into the body where they can multiply and cause harm. While many people carry these bacteria on their skin or in their nose, an actual infection develops only when the bacteria find a way to get past the body’s natural defenses.[3]
The most common way staph bacteria enter the body is through breaks in the skin. This can happen through cuts, scrapes, burns, or surgical wounds. Even tiny breaks in the skin that you might not notice can be enough for bacteria to get in. Places where the skin is already damaged—such as areas affected by eczema, insect bites, or where medical needles have been inserted—are especially vulnerable to staph infections.[1]
Staph bacteria spread easily from person to person through direct skin-to-skin contact. This is why outbreaks can happen in places where people have close physical contact with each other, like in contact sports, daycare centers, or schools. The bacteria can also spread indirectly when someone touches an object that has bacteria on it—such as a towel, razor, sports equipment, or even a remote control—and then touches a break in their own skin.[3][12]
In healthcare settings, staph bacteria can be introduced into the body through medical devices. Catheters, breathing tubes, feeding tubes, and implanted devices like pacemakers or artificial joints can all serve as pathways for bacteria to enter the body. Once bacteria attach to these devices, they can be very difficult to eliminate.[3]
Food poisoning from staph bacteria happens when the bacteria grow in food and produce toxins. If someone who carries staph bacteria on their hands prepares food without washing their hands properly, the bacteria can contaminate the food. When the food is left at room temperature, the bacteria multiply and release toxins that make people sick when they eat the food.[2]
Who Is at Higher Risk?
While anyone can develop a staphylococcal infection, certain groups of people are more likely to get one. Understanding these risk factors can help people take extra precautions to protect themselves.[3]
People with weakened immune systems face a higher risk of staph infections. This includes individuals who have HIV, those undergoing chemotherapy for cancer, people taking medicines to prevent organ rejection after a transplant, and anyone whose body’s natural defenses are not working at full strength. When the immune system cannot fight off bacteria effectively, even a small number of staph bacteria can cause a serious infection.[3]
Patients in hospitals or those who have recently had surgery are at increased risk. Surgery creates wounds that can serve as entry points for bacteria. Additionally, hospitals contain many sick people and healthcare workers who may be carrying staph bacteria, increasing the chances of exposure. People with medical tubes or devices in their bodies—such as urinary catheters, feeding tubes, breathing tubes, or implanted devices like pacemakers or artificial joints—have pathways through which bacteria can enter.[2][12]
Individuals with certain chronic health conditions have elevated risk. People with diabetes, cancer, vascular disease, eczema, or lung disease are more prone to developing staph infections. These conditions can affect the body’s ability to fight infections or can create breaks in the skin where bacteria can enter.[3][4]
People who inject drugs are at significantly higher risk because needles can introduce bacteria directly into the body. Similarly, people on dialysis for kidney problems face increased risk because the dialysis process requires regular access to the bloodstream.[12]
Athletes who participate in contact sports face higher risk due to frequent skin-to-skin contact with others and the sharing of equipment. Breastfeeding mothers can develop mastitis, a breast infection caused by staph bacteria. Infants, children, and elderly people may also be more vulnerable to certain types of staph infections.[2][12]
People who live with or have close contact with someone who has a staph infection are more likely to become infected themselves. Healthcare workers are also at higher risk because they frequently come into contact with patients who may be carrying staph bacteria.[2]
Recognizing the Symptoms
The symptoms of a staphylococcal infection depend greatly on where in the body the infection occurs and how serious it is. Because staph can infect many different parts of the body, the symptoms can vary widely from person to person.[1][2]
Skin Infections
Skin infections are by far the most common type of staph infection. On the skin, staph infections often look like pimples or boils. They appear as red, swollen, painful bumps or lumps that may be filled with pus or other fluid. The infected area often feels warm or hot to the touch. Sometimes fluid or pus leaks out of these sores.[2][3]
Several specific types of skin infections can be caused by staph bacteria. Impetigo appears as sores, usually on the face, that burst and leave a yellow, crusty appearance. This type of infection is common in children. Folliculitis shows up as pus-filled bumps around hair follicles that look like pimples but are typically itchy and develop into crusty sores. Boils, also called furuncles, are deep pockets of pus that form under the skin, often under the arms or around the groin or buttocks. When several boils join together, especially around the neck area, they form a larger infection called a carbuncle.[1][5]
Cellulitis is another type of skin infection where the skin becomes hot, red, and swollen. The affected area often spreads and can be quite large. Children may develop staphylococcal scalded skin syndrome, where the skin becomes red and looks like it has been burned, with blisters that can peel off.[2][5]
Deeper Infections
When staph bacteria get deeper into the body, the infections become much more serious and the symptoms more severe. Bone infections, called osteomyelitis, cause pain, swelling, warmth, and redness in the area over the infected bone. People with bone infections typically also have chills and fever.[2][3]
If staph bacteria reach the lungs and cause pneumonia, symptoms include high fever, chills, and a cough that does not get better. The person may cough up bloody mucus and experience chest pain and shortness of breath. This type of pneumonia can cause abscesses to form in the lungs, making breathing very difficult.[2][3]
When staph infects the heart valves, a condition called endocarditis develops. This causes flu-like symptoms such as fever, chills, and extreme tiredness. It also causes more specific heart-related symptoms like rapid heartbeat, shortness of breath, and fluid buildup in the arms or legs. Endocarditis is life-threatening and can lead to heart failure or stroke.[3]
A blood infection, called septicemia or bacteremia, occurs when staph bacteria get into the bloodstream. This causes high fever and can lead to dangerously low blood pressure, a condition called septic shock. Blood infections can quickly become life-threatening and can spread the bacteria to any organ in the body.[2][3]
Food Poisoning
Staphylococcal food poisoning causes nausea and vomiting, diarrhea, and fever. These symptoms usually start quickly after eating contaminated food. While uncomfortable, this type of staph illness typically gets better on its own and does not require antibiotics because it is caused by toxins the bacteria produce, not by the bacteria themselves growing in the body.[2]
Special Conditions
Breastfeeding mothers can develop mastitis, an infection of the breast tissue that causes pain, redness, and abscesses in the breast. Toxic shock syndrome is a rare but very serious condition where staph bacteria release toxins into the bloodstream, causing high fever, sudden dangerously low blood pressure, vomiting, diarrhea, confusion, and a rash that looks like a sunburn. This condition can cause organs to fail and can be fatal.[2][3]
Preventing Staphylococcal Infections
Because staph bacteria are so common and spread easily, preventing infections requires consistent attention to hygiene and wound care. While it is impossible to completely avoid staph bacteria in the environment, there are many effective steps people can take to reduce their risk of infection.[5]
Hand Hygiene
The single most important prevention measure is regular, thorough hand washing. Washing hands with soap and water for at least 20 seconds helps remove staph bacteria from the skin. It is especially important to wash hands before touching your face, before eating, after using the bathroom, and after touching surfaces in public places. If soap and water are not available, alcohol-based hand sanitizers that contain at least 60% alcohol can be used as an alternative. However, the hand sanitizer must be rubbed over all surfaces of the hands until they are dry to be effective.[5][12]
People should always wash their hands before and after touching any wound or bandage, even if they are wearing gloves. After handling dirty laundry or bandages, hand washing is essential to prevent spreading bacteria to other surfaces or people.[12][19]
Wound Care
Any break in the skin—cuts, scrapes, burns, or surgical wounds—should be cleaned promptly with soap and water. Once cleaned, wounds should be covered with clean, dry bandages. Keeping wounds covered until they heal completely helps prevent staph bacteria from getting in. Bandages should be changed regularly, especially if they become wet or dirty. Used bandages should be thrown away immediately in a sealed bag to prevent the spread of any bacteria.[12][19]
If a wound becomes red, swollen, increasingly painful, or starts producing pus, medical attention should be sought. People should never try to squeeze, pop, or drain infected sores themselves, as this can push bacteria deeper into the body and spread the infection.[12]
Personal Hygiene
Taking regular baths or showers and using soap to clean the entire body helps reduce the number of staph bacteria on the skin. Clean clothes should be worn daily, and dirty clothes should not be put back in closets or drawers until they have been washed.[19]
Personal items should never be shared with others. This includes towels, washcloths, razors, clothing, cosmetics, and athletic equipment. Sharing these items can easily transfer staph bacteria from one person to another. In gyms and sports facilities, equipment should be wiped down before and after use.[5][12]
Laundry and Household Cleaning
Laundry that may be contaminated with staph bacteria requires special handling. When changing sheets or handling dirty clothes, especially items that have touched wounds or infected areas, hold them away from your body to prevent bacteria from transferring to your clean clothes. Washing laundry in warm or hot water and using bleach when possible helps kill bacteria. Clothes should be completely dried in a warm or hot dryer.[19]
Frequently touched surfaces in the home should be cleaned regularly with household disinfectants or bleach solutions. This includes doorknobs, light switches, phones, remote controls, toilets, sinks, tubs, showers, and kitchen counters. These surfaces should be wiped with disinfectant and allowed to air dry.[19]
Activity Restrictions
People with active staph infections on their skin should avoid certain activities until the infection has healed. They should not participate in contact sports, visit public gyms, use saunas or hot tubs, or swim in public pools. These restrictions help prevent spreading the infection to others.[19]
Healthcare Settings
In hospitals and healthcare facilities, patients and visitors should ensure that all healthcare workers wash their hands or use hand sanitizer before touching them. If someone has been identified as carrying resistant staph bacteria like MRSA, they may be placed in isolation to prevent spreading the bacteria to other patients.[6]
How Infections Develop in the Body
Understanding what happens inside the body during a staphylococcal infection helps explain why these infections can be so varied and sometimes so serious. The changes that occur at the biological level are what cause the symptoms people experience.[6]
When staph bacteria enter the body through a break in the skin, the body’s immune system responds immediately. White blood cells rush to the area to fight off the invading bacteria. This immune response causes inflammation, which is why infected areas become red, warm, swollen, and painful. The pus that often forms in staph infections is actually a mixture of dead bacteria, dead white blood cells, and fluid from the body’s inflammatory response.[2]
Staph bacteria have developed various ways to protect themselves and survive in the body. Some strains produce a substance that helps them stick to body tissues or medical devices, making them very hard to remove. This is particularly problematic when bacteria form communities on implanted medical devices like artificial joints or heart valves. These bacterial communities, called biofilms, are very resistant to antibiotics and the body’s immune defenses.[6]
Staph bacteria can also produce toxins—harmful substances that damage tissues and cause illness. Different strains of staph produce different toxins. Some toxins destroy skin cells, which is what causes the skin damage seen in conditions like impetigo or scalded skin syndrome. Other toxins can affect the entire body when released into the bloodstream, causing serious conditions like toxic shock syndrome. The toxins responsible for food poisoning act on the digestive system, triggering nausea and vomiting.[6]
If staph bacteria get into the bloodstream, they can travel throughout the body and settle in various organs. When bacteria lodge in bone tissue, they cause osteomyelitis, which involves inflammation and destruction of bone. In the heart, bacteria can attach to heart valves and form growths made up of bacteria, blood clots, and inflammatory cells. These growths interfere with the heart’s normal function and can break off and travel to other parts of the body, causing further damage.[2]
In the lungs, staph bacteria can cause pneumonia by multiplying in the air sacs where oxygen is normally exchanged. The bacteria trigger an inflammatory response that fills these air sacs with fluid and pus, making it difficult to breathe. The bacteria can also form pockets of infection called abscesses in the lung tissue.[2]
The body normally tries to wall off bacterial infections to prevent them from spreading. This is why abscesses form—the body creates a barrier around the infected area. However, if the infection is severe or if the person’s immune system is weakened, the bacteria can break through these barriers and spread to other parts of the body. When bacteria multiply rapidly in the bloodstream and release large amounts of toxins, the body can go into septic shock, where blood pressure drops dangerously and organs begin to fail.[2]
The interaction between staph bacteria and the body’s immune system is complex. In healthy people with strong immune systems, the body can often control and eliminate staph bacteria before they cause serious problems. However, people with weakened immune systems may not be able to mount an effective response, allowing bacteria to multiply and spread more easily. This is why people with conditions like diabetes, cancer, or HIV are at higher risk for severe staph infections.[3]
