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Bacterial skin infections

Author: Dr Amanda Oakley, Dermatologist, Waikato Hospital, Hamilton, New Zealand, 2002.

Table of contents


Some bacteria live on normal skin and cause no harm, such as some Staphylococcus species, Corynebacterium spp., Brevibacterium spp and Acinetobacter. Propionibacteria live in the hair follicles of adult skin and contribute to acne. See DermNet's page on the microorganisms found on the skin.

Some bacteria invade normal skin, broken skin from eczema/dermatitis or wounds (causing wound infection). Bacteria, like viruses, may also sometimes result in exanthems (rashes).

Which bacteria cause skin infection? 

Staphylococcus aureus

Streptococcus pyogenes

Corynebacterium species

Less common bacteria may also cause infection with skin signs. These include:

Tick-borne bacterial infections include:

Other conditions sometimes caused by or associated with bacterial infection include:

Which tests should be done?

Laboratory tests for bacterial infections may include:

  • Full blood count: bacterial infection often raises the white cell count with increased neutrophils
  • C-reactive protein (CRP): elevated > 50 in serious bacterial infections
  • Procalcitonin: blood test marker for generalised sepsis due to bacterial infection
  • Serology: tests ten days apart to determine immune response to a particular organism
  • Polymerase chain reaction (PCR) and ELISA tests for specific organisms
  • Blood culture: if high fever > 38C
  • A swab of the inflamed site, such as throat, skin lesions for culture.

How are bacterial infections treated?

Minor bacterial infections may resolve without treatment. However, persistent and serious bacterial infections are treated with antibiotics. These are available for localised topical use (creams, gels, solutions), such as antibiotics for acne, or as systemic treatment as tablets, capsules and intramuscular or intravenous injections.

It is best to take samples to test which organism is responsible for an infection before commencing antibiotics. If the infection is serious (eg, if meningococcal disease is suspected), immediate treatment with a broad-spectrum antibiotic may commence. Once the specific organism causing infection has been determined, the antibiotic may be changed to a narrow-spectrum antibiotic directed against this organism.

Antibiotics have important individual risks and societal impact and should not be prescribed or taken if they are not required or if they are unlikely to be of benefit, for example, if the infection is viral in origin. Adverse reactions include cutaneous effects.



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