Bacterial skin infections

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


Bacterial skin infections
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Categories:
Bacterial skin infections
ICD-10-CM:
A49.9
ICD-11 MMS:
IC41
SNOMED CT:
128936008

Introduction

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 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 10 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
  • Swab of inflamed site, eg, 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), eg 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 meningococcal disease is suspected), immediate treatment with 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 infection is viral in origin. 

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