What Is a Staph Infection?

Staphylococcal (staph) infection is caused when bacteria called Staphyloccocus enters the body, usually through a skin cut or wound. Staphyloccocus aureus is the most common type to infect humans, though there are more than 30 others. While staph normally lives in the nose or on the skin of some healthy individuals without consequence, infections can cause abscesses, cellulitis, or other skin concerns, and can less commonly infect the bloodstream or other organs (e.g., heart, lung, or bone).

In the majority of cases, antibiotics can successfully treat staph infections. However, some cases can be resistant and even life-threatening.

Staph Infection Symptoms

The symptoms of a staph infection depend on the type of infection it is causing. Staph is most commonly associated with skin infections, such as abscesses, folliculitis, furuncle, carbuncle, impetigo, and cellulitis, to name a few.

Symptoms such as swelling, warmth, redness, and pain or soreness within or surrounding the infected area are common. Sometimes, a fever is present and the infected skin may drain pus.

If the staph bacteria enter the bloodstream, sepsis may develop, which is very serious and potentially fatal.

Other serious staph infections (of which the symptoms are unique to the affected tissue or organ) include:

• Osteomyelitis (infection of the bone)
• Pneumonia (infection of the lung)
• Endocarditis (infection of the heart valve)
• Meningitis (infection of the membranes that cover the brain and spinal cord)
• Epidural abscess (infection of the epidural space)
• Septic arthritis (infection of a joint)
• Prosthetic joint infections (infection of an artifical joint)

Staph may also cause:

• Toxic shock syndrome (TSS)
• Scalded skin syndrome
• Food poisoning
• Mastitis
• Catheter-associated urinary tract infection

Causes

Many different types of staph live on the human body (this is called colonization). For example, Staphylococcos aureus colonizes the noses of about 30% of healthy people and the skin of about 20% of people.

Besides living on people, staph can live on objects, such as doorknobs or athletic equipment. A person can become colonized with staph by simply touching the skin of someone who is colonized or by touching or sharing a contaminated object (e.g., a towel or razor).

That said, colonization is not the same as an infection. Being colonized with staph causes no symptoms. On the other hand, when staph enters the body causing an infection, symptoms do occur. The bacteria most commonly find their way through a break in the skin (e.g., a minor cut from shaving or a wound from trauma).

While anyone can develop a staph infection, there are factors that increase a person's risk.

Some of these risk factors include:

• Being very young or very old
• Having a chronic skin or lung disease
• Having an open wound
• Being on a drug that weakens your immune system (e.g., corticosteroids)
• Using injected drugs, such as opioids
• Being hospitalized or living in a long-term care facility, like a nursing home
• Having diabetes mellitus or HIV
• Having a transplanted organ or an implanted medical device (e.g., artificial heart valve, pacemaker, or joint)
• Being on dialysis
• Having long-term intravascular access (e.g., having a chemotherapy port)

Diagnosis

Diagnosis of a staph infection requires a medical history, physical exam, and often tests, like a bacterial culture or various blood tests.

History and Physical Examination

The history and physical examination will be tailored to your unique symptoms. For example, for a potential skin infection, your healthcare provider will inspect the affected skin for warmth, redness, tenderness, and drainage. They will also inquire about symptoms that may indicate a more serious infection (e.g., fever or body aches), as well as potential exposures to and risk factors for staph.

A key aspect of the physical examination is an evaluation of your vital signs—blood pressure, heart rate, breathing rate, and temperature—as abnormalities can indicate a serious and/or systemic (whole-body) infection of some kind.

Culture and Other Tests

A bacterial culture is used to definitively diagnose a skin infection caused by staph bacteria. Other tests that may be ordered to assess the severity of the infection include blood tests like a complete blood count (CBC), a comprehensive metabolic panel (CMP), and a C-reactive protein level.

Imaging tests to evaluate certain organs (e.g., an echocardiogram for endocarditis or a chest X-ray for pneumonia) may also be ordered.

Treatment

Once diagnosed with a staph infection, antibiotic therapy is the mainstay treatment.

Antibiotics can be given topically (on the skin), orally (by mouth) or intravenously (through the vein).

The specific antibiotic chosen depends on two main factors:

• The severity of the infection
• Whether the staph bacteria is resistant to any antibiotics

Severity

Mild or moderate staph infections can generally be treated with topical or oral antibiotics.

For example, a topical antibiotic like Bactroban (mupirocin) may be considered to treat mild cases of impetigo and folliculitis. Likewise, an oral antibiotic, such as Keflex (cephalexin), may be used to treat mastitis or nonpurulent cellulitis (cellulitis with no drainage of pus and no associated abscess).

Intravenous antibiotics, such as Vancocin (vancomycin), which are given directly into the bloodstream, are required to treat severe staph infections, like osteomyelitis, pneumonia, and sepsis.

Resistance

While many staph infections can be treated with methicillin or a similar antibiotic, like Keflex (cephalexin), some staph bacteria are resistant to methicillin. These bacteria are called methicillin-resistant Staphylococcus aureus (MRSA).

To determine which antibiotics are effective against the staph, healthcare providers can perform an antibiotic susceptibility test in a lab setting.

Then, based on where the infection was contracted, healthcare providers can choose to treat the MRSA infection with a certain oral or intravenous antibiotic.

Hospital-acquired MRSA infections are usually serious and potentially life-threatening. They require treatment with an intravenous antibiotic like Vancocin (vancomycin) or Cubicin (daptomycin). Once discharged from the hospital, people often go home with oral antibiotics or intravenous antibiotics administered through a PICC line.

Community-acquired MRSA infections tend to not be as serious or fatal. They can often be treated with oral antibiotics, like Bactrim (trimethoprim-sulfamethoxazole) or Cleocin (clindamycin).

Other Therapies

It's important to keep in mind that the treatment of staph infections may involve additional therapies along with antibiotics.

For example, an abscess usually requires incision and drainage (where the pus is removed). Similarly, an infected joint (septic arthritis) usually involves drainage of the joint space, in addition to antibiotic therapy.

For an infected bone or prosthetic joint, surgical debridement is required along with antibiotics.

Surgical decompression, along with antibiotics, is used to treat staph epidural abscesses.

Prevention

Good hand and personal hygiene are at the crux of preventing staph infections. This means thoroughly washing your hands with soap and water, avoiding sharing personal items with others, and covering any wounds with a bandage until they are healed.

For people in the hospital with MRSA infections, isolation precautions—such as wearing disposable gowns and gloves—help prevent the spread of infection to the staff and other patients. Disposable equipment, such as disposable stethoscopes, are also commonly used.

A Words From Verywell

The bottom line here is that while usually a harmless germ, Staphylococcus aureus can lead to serious infections. To be proactive, wash your hands thoroughly and frequently and seek medical attention right away for any signs of infection, such as skin redness or warmth, drainage, fever, chills, body aches, or other unusual symptoms.