Staphylococcal infections - Diagnosing staphylococcal infections

Staphylococcal infections are diagnosed in different ways depending on your symptoms and the type of infection you have.

Staphylococcal skin infections

A staphylococcal skin infection is often diagnosed by examining the affected area of skin. A small piece of tissue may also be removed using a swab and tested for Staphylococcus aureus (S. aureus) bacteria.

Invasive staphylococcal infections

There are three main goals in diagnosing an invasive staphylococcal infection:

• to confirm whether the infection has been caused by S. aureus bacteria and whether the bacteria have developed resistance to one or more antibiotics 
• to determine the source of the infection
• to determine which other functions of the body have been affected and how badly

To do this, a number of tests may be carried out including:

• blood tests
• urine tests
• stool sample tests
• blood pressure tests
• a wound culture test - where a small sample of tissue, skin or fluid is taken from the affected area for testing
• respiratory secretion testing - which involves testing a sample of saliva, phlegm or mucus
• imaging studies, such as an X-ray or computerised tomography (CT) scan, or an echocardiogram - where sound waves are used to scan the valves and chambers of the heart
• kidney and liver function tests
• a lumbar puncture - where a sample of cerebrospinal fluid is removed from your back for testing

Staphylococcal food poisoning

Staphylococcal food poisoning can be diagnosed by taking a sample of your stools (faeces) and testing it for bacteria. However, in most food poisoning cases there is usually no need to carry out a diagnosis as it passes within a few days.

You only need to see your GP if:

• your symptoms are severe and not getting better
• you have symptoms of severe dehydration, such as sunken eyes and are unable to urinate
• there has been an outbreak of similar cases of food poisoning linked to a possible source of contamination