What are the symptoms and signs of a Staph infection?
Staphylococcal disease of the skin usually results in a localized collection of pus, known as an abscess, boil, or furuncle, depending upon the exact type of lesion that is present. The affected area may be red, swollen, and painful. Drainage or pus is common.
When Staph is in the blood (bacteremia or sepsis), it can cause high fevers, chills, and low blood pressure. Deep abscesses, pneumonia, osteomylitis, and most other internal infections are only seen by X-ray and other imaging techniques or are not visible at all (for example, toxic shock, food poisoning).
How are Staph infections diagnosed?
In cases of minor skin infections, staphylococcal infections are commonly diagnosed by their appearance without the need for laboratory testing. More serious staphylococcal infections such as infection of the bloodstream, pneumonia, and endocarditis require culturing of samples of blood or infected body fluids. The laboratory establishes the diagnosis and performs special tests to determine which antibiotics are effective against the bacteria.
Diagnosis of staph infections begins with attempting to culture the bacteria from an infected site. Any area with pus, crusty drainage, or blisters should be cultured. Blood from patients with sepsis, toxic shock, or pneumonia should be cultured. Standard microbiological techniques (growth on Baird-Parker agar plates and a positive coagulase test) identify staph. S. aureus lyses red blood cells in blood agar plates (hemolytic staph) while S. epidermidis does not (non hemolytic staph).
All staph should be further tested to see if the bacteria are resistant to the antibiotic methicillin (and other antibiotics) and thus determine if the organisms are MRSA (methicillin resistant Staphylococcus aureus). This test is important as MRSA organisms are resistant to many antibiotics usually prescribed for staph infections.
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