Skin Home > Staph Infection Causes

There are a few strains of Staphylococcus bacteria that can cause staph infections in humans. The most common type is associated with a strain known as Staphylococcus aureus. Other strains include Staphylococcus epidermidis, which causes many hospital-related infections, and Staphylococcus saprophyticus, which is a common cause of urinary tract infections in young adult women.

What Causes a Staph Infection?

Staphylococcus is a group of bacteria commonly found on the skin, mucous membranes, and within the bowels of healthy people. There are dozens of species within the Staphylococcus genus.
Most of the time, Staphylococcus bacteria cause no problems. In fact, about 25 to 30 percent of the population is colonized in the nose. Colonization refers to a condition when bacteria are present on the skin or within the body but are not causing an infection.
When Staphylococci do cause an infection, it is commonly referred to as a Staphylococcus infection, or staph infection for short.
Staph bacteria are one of the most common causes of skin infections in the United States. Most of these infections are minor (such as pimples and boils) and can be treated without antibiotics. However, staph bacteria can cause serious infections, such as surgical wound infections, bloodstream infections, and pneumonia.

Causes of Human Staphylococcal Infections

There are only a few different types of Staphylococcus bacteria known to cause infections in humans. Four of them include:
  • Staphylococcus aureus (S. aureus), the most common type of staph infection
  • Staphylococcus epidermidis, a primary cause of infections in the hospital
  • Staphylococcus saprophyticus, a common cause of urinary tract infections (UTIs) in young adult women
  • Staphylococcus lugdunensis, infections that can range from minor to life-threatening.
Some Staphylococcus bacteria are resistant to certain antibiotics. Methicillin-resistant Staphylococcus aureus, or MRSA for short, is a type of Staphylococcus that is resistant to antibiotics called beta-lactams.
Beta-lactam antibiotics include methicillin and other, more common antibiotics, such as oxacillin, penicillin, and amoxicillin (Amoxil®). While 25 to 30 percent of the population is colonized with staph, approximately 1 to 2 percent is colonized with MRSA.
S. hominis, S. haemolyticus, S. warneri, and S. simulans are four other types that can cause staph infections in humans, but they are more rare.
Written by/reviewed by:
Last reviewed by: Arthur Schoenstadt, MD
Last updated/reviewed:
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