Staphylococcal infections

Staphylococcal infections are a group of infections caused by the bacterium Staphylococcus. You may have heard them referred to as staph infections.

The spectrum of staph infections can range from a minor boil or skin abscess to life-threatening infections such as septicaemia (infection of the blood) or endocarditis (infection of the lining of the heart).

There are many types of staphylococci, but most infections are caused by Staphylococcus aureus (S. aureus). S. aureus is common and often found in the nose or on the skin. Most of the time the bacteria do not cause any symptoms – this is referred to as colonisation.

Types of infection

Staph infections are caused when bacteria get into a break or cut in the skin. Depending how deep it goes, the type of infection can be broadly classified into two groups:

• skin and soft tissue infections - such as impetigo or cellulitis 
• invasive infections - such as septicaemia (blood poisoning), septic arthritis (joint infection) or endocarditis (infection of the lining of the heart)

Skin infections are most common and usually cause symptoms such as boils or abscesses - painful, pus-filled lumps on the surface or just under the skin. This can lead to impetigo, which forms a crust on the skin, or cellulitis, which causes redness, swelling and pain in the skin and underlying tissue.  

In some cases an invasive infection can develop as a complication of a skin infection. The symptoms are more severe and wide-ranging and can include:

• a high temperature (fever) of 38 degrees C (100.4 degrees F) or above
• low blood pressure, which will cause you to feel dizzy when you stand up
• confusion or disorientation
• shortness of breath

Read more about the symptoms of staphylococcal infections.

Eating food contaminated with S. aureus bacteria will give you food poisoning. This normally develops after eating food, usually meat, that hasn't been cooked or stored properly.

Treating infections

Skin infections are usually mild and can be treated using antibiotic tablets or creams.

Invasive infections are more serious and usually treated in hospital with antibiotic injections.

Read more about treating staphylococcal infections.

Once the bacteria penetrate the skin and enter the blood or organs, they rapidly multiply and release toxins, which can cause other organs to stop working and a massive drop in blood pressure (toxic shock, a type of septic shock). These complications are life-threatening. 

How successful treatment is for people with invasive staph infections will depend on:

• the person’s age
• where the infection has spread to
• whether the infection has caused complications
• whether or not the person has any pre-existing health conditions, such as diabetes, a weakened immune system or heart disease

Preventing infection

The best way to prevent a staphylococcal infection is to regularly wash your hands and make sure any cuts and grazes are kept clean.

Read more about preventing staphylococcal infections.

Who gets staph infections?

Staphylococcal skin infections are common, particularly among children, teenagers and young adults. Impetigo, for example, accounts for around 1 in 10 of all reported skin conditions in children.

Invasive staphylococcal infections are much less common. In England, it is estimated that about 1 in 3,300 people will develop an invasive infection in any given year.

You are more at risk of developing an invasive infection if you:

• are having dialysis - used to treat people with advanced chronic kidney disease; the way dialysis is performed can sometimes allow bacteria to get inside the body
• have a weakened immune system due to a condition, such as HIV or taking medication to suppress your immune system (immunosuppressants)

Read more about the causes of staphylococcal infections.