Staph infections are caused by staphylococcus bacteria, types of germs commonly found on the skin or in the nose of even healthy individuals. Most of the time, these bacteria cause no problems or result in relatively minor skin infections.

But staph infections can turn deadly if the bacteria invade deeper into your body, entering your bloodstream, joints, bones, lungs or heart. A growing number of otherwise healthy people are developing life-threatening staph infections.

Treatment usually involves antibiotics and drainage of the infected area. However, some staph infections no longer respond to common antibiotics.

Staph infections can range from minor skin problems to endocarditis, a life-threatening infection of the inner lining of your heart (endocardium). Because of this, signs and symptoms of staph infections vary widely, depending on the location and severity of the infection.

Skin infections

Skin infections caused by staph bacteria include:

• Boils. The most common type of staph infection is the boil, a pocket of pus that develops in a hair follicle or oil gland. The skin over the infected area usually becomes red and swollen.

  If a boil breaks open, it will probably drain pus. Boils occur most often under the arms or around the groin or buttocks.

• Impetigo. This contagious, often painful rash can be caused by staph bacteria. Impetigo usually features large blisters that may ooze fluid and develop a honey-colored crust.
• Cellulitis. Cellulitis — an infection of the deeper layers of skin — causes skin redness and swelling on the surface of your skin. Sores or areas of oozing discharge may develop, too.
• Staphylococcal scalded skin syndrome. Toxins produced as a result of a staph infection may lead to staphylococcal scalded skin syndrome. Affecting mostly babies and children, this condition features a fever, a rash and sometimes blisters. When the blisters break, the top layer of skin comes off — leaving a red, raw surface that looks like a burn.

Food poisoning

Staph bacteria are one of the most common causes of food poisoning. Symptoms come on quickly, usually within hours of eating a contaminated food. Symptoms usually disappear quickly, too, often lasting just half a day.

A staph infection in food usually doesn't cause a fever. Signs and symptoms you can expect with this type of staph infection include:

• Nausea and vomiting
• Diarrhea
• Dehydration
• Low blood pressure

Bacteremia

Also known as a bloodstream infection, bacteremia occurs when staph bacteria enter a person's bloodstream. A fever and low blood pressure are signs of bacteremia. The bacteria can travel to locations deep within your body, to produce infections affecting:

• Internal organs, such as your brain, heart or lungs
• Bones and muscles
• Surgically implanted devices, such as artificial joints or cardiac pacemakers

Toxic shock syndrome

This life-threatening condition results from toxins produced by some strains of staph bacteria and has been linked to certain types of tampons, skin wounds and surgery. It usually develops suddenly with:

• A high fever
• Nausea and vomiting
• A rash on your palms and soles that resembles a sunburn
• Confusion
• Muscle aches
• Diarrhea
• Stomach pain

Septic arthritis

Septic arthritis is often caused by a staph infection. The bacteria often target the knees, shoulders, hips, and fingers or toes. Signs and symptoms may include:

• Joint swelling
• Severe pain in the affected joint
• Fever

When to see a doctor

Go to the doctor if you or your child has:

• An area of red, irritated or painful skin
• Pus-filled blisters
• Fever

You may also want to consult your doctor if:

• Skin infections are being passed from one family member to another
• Two or more family members have skin infections at the same time

Many people carry staph bacteria and never develop staph infections. However, if you develop a staph infection, there's a good chance that it's from bacteria you've been carrying around for some time.

These bacteria can also be transmitted from person to person. Because staph bacteria are so hardy, they can live on objects such as pillowcases or towels long enough to transfer to the next person who touches them.

Staph bacteria are able to survive:

• Drying
• Extremes of temperature
• Stomach acid

A variety of factors — including the status of your immune system to the types of sports you play — can increase your risk of developing staph infections.

Underlying health conditions

Certain disorders or the medications used to treat them can make you more susceptible to staph infections. People who may be more likely to get a staph infection include those with:

• Diabetes who use insulin
• HIV/AIDS
• Kidney failure requiring dialysis
• Weakened immune systems — either from a disease or medications that suppress the immune system
• A transplant
• Cancer, especially those who are undergoing chemotherapy or radiation
• Skin damage from conditions such as eczema, insect bites or minor trauma that opens the skin
• Respiratory illness, such as cystic fibrosis or emphysema

Current or recent hospitalization

Despite vigorous attempts to eradicate them, staph bacteria remain present in hospitals, where they attack the most vulnerable, including people with:

• Weakened immune systems
• Burns
• Surgical wounds

Invasive devices

Staph bacteria can travel along the medical tubing that connects the outside world with your internal organs. Examples include:

• Dialysis tubing
• Urinary catheters
• Feeding tubes
• Breathing tubes
• Intravascular catheters

Contact sports

Staph bacteria can spread easily through cuts, abrasions and skin-to-skin contact. Staph infections may also spread in the locker room through shared razors, towels, uniforms or equipment.

Unsanitary food preparation

Food handlers who don't properly wash their hands can transfer staph from their skin to the food they're preparing. Foods that are contaminated with staph look and taste normal.

If staph bacteria invade your bloodstream, you may develop a type of infection that affects your entire body. Called sepsis, this infection can lead to septic shock — a life-threatening episode with extremely low blood pressure.

These commonsense precautions can help lower your risk of developing staph infections:

• Wash your hands. Careful hand-washing is your best defense against germs. Wash your hands with soap and water briskly for at least 20 seconds. Then dry them with a disposable towel and use another towel to turn off the faucet. If your hands aren't visibly dirty, you can use an alcohol-based hand sanitizer.

  Wash your hands with soap and water regularly, such as before, during and after making food; after handling raw meat or poultry; before eating; after using the bathroom; and after touching an animal or animal waste.

• Keep wounds covered. Keep cuts and abrasions clean and covered with sterile, dry bandages until they heal. The pus from infected sores often contains staph bacteria, and keeping wounds covered will help keep the bacteria from spreading.
• Reduce tampon risks. Toxic shock syndrome is caused by staph bacteria. Tampons left in for long periods can be a breeding ground for staph bacteria. You can reduce your chances of getting toxic shock syndrome by changing your tampon frequently — at least every four to eight hours. Use the lowest absorbency tampon you can. Try to alternate tampons with sanitary napkins whenever possible.
• Keep personal items personal. Avoid sharing personal items such as towels, sheets, razors, clothing and athletic equipment. Staph infections can spread on objects, as well as from person to person.

• Wash clothing and bedding in hot water. Staph bacteria can survive on clothing and bedding that isn't properly washed. To get bacteria off clothing and sheets, wash them in hot water whenever possible.

  Also, use bleach on any bleach-safe materials. Drying in the dryer is better than air-drying, but staph bacteria may survive the clothes dryer.

• Take food safety precautions. Wash your hands before handling food. If food will be out for a while, make sure that hot foods stay hot — above 140 F (60 C) — and that cold foods stay at 40 F (4.4 C) or below. Refrigerate leftovers as soon as possible. Wash cutting boards and counters with soap and water.

To diagnose a staph infection, your doctor will:

• Perform a physical exam. During the exam, your doctor will closely examine any skin lesions you may have.
• Collect a sample for testing. Most often, doctors diagnose staph infections by checking a tissue sample or nasal secretions for signs of the bacteria.
• Other tests. If you're diagnosed with a staph infection, your doctor may order an imaging test called an echocardiogram to check if the infection has affected your heart. Your doctor may order other imaging tests, depending on your symptoms and the exam results.

Treatment of a staph infection may include:

• Antibiotics. Your doctor may perform tests to identify the staph bacteria behind your infection, and to help choose the antibiotic that will work best. Antibiotics commonly prescribed to treat staph infections include certain cephalosporins such as cefazolin; nafcillin or oxacillin; vancomycin; daptomycin (Cubicin); telavancin (Vibativ); or linezolid (Zyvox).

  Vancomycin increasingly is required to treat serious staph infections because so many strains of staph bacteria have become resistant to other traditional medicines. But vancomycin and some other antibiotics have to be given intravenously.

  If you're given an oral antibiotic, be sure to take it as directed, and to finish all of the medication prescribed by your doctor. Ask your doctor what signs and symptoms you should watch for that might indicate your infection is worsening.

• Wound drainage. If you have a skin infection, your doctor will likely make an incision into the sore to drain fluid that has collected there.
• Device removal. If your infection involves a device or prosthetic, prompt removal of the device is needed. For some devices, removal might require surgery.

Antibiotic resistance

Staph bacteria are very adaptable, and many varieties have become resistant to one or more antibiotics. For example, only about 5% of today's staph infections can be cured with penicillin.

The emergence of antibiotic-resistant strains of staph bacteria — often described as methicillin-resistant Staphylococcus aureus (MRSA) strains — has led to the use of IV antibiotics, such as vancomycin or daptomycin, with the potential for more side effects.

While you may initially consult your family doctor, he or she may refer you to a specialist, depending on which of your organ systems is affected by the infection. For example, you may be referred to a doctor trained in treating skin conditions (dermatologist), heart disorders (cardiologist) or infectious diseases.

What you can do

You may want to write a list that includes:

• Detailed descriptions of your symptoms
• Information about medical problems you've had
• Information about the medical problems of your parents or siblings
• All the medications and dietary supplements you take
• Questions you want to ask the doctor

For a staph infection, some basic questions to ask your doctor include:

• What's the most likely cause of my symptoms?
• What kind of tests do I need?
• What's the best treatment for a staph infection?
• Am I contagious?
• How can I tell if my infection is getting better or worse?
• Are there any activity restrictions that I need to follow?
• I have other health conditions. How can I best manage these conditions together?
• Do you have any brochures or other printed material that I can take home with me? What websites do you recommend?

What to expect from your doctor

Your doctor will likely ask you a number of questions, such as:

• When did you first notice your symptoms? Could you describe them to me?
• How severe are your symptoms?
• Have you been around anyone with a staph infection?
• Do you have any implanted medical devices, such as an artificial joint or a pacemaker?
• Do you have any ongoing medical conditions, including an impaired immune system?
• Have you recently been in the hospital?
• Do you play contact sports?

What you can do in the meantime

If you suspect you have a staph infection on your skin, keep the area clean and covered until you see your doctor so that you don't spread the bacteria. And, until you know whether or not you have staph, don't prepare food.