Skin and soft tissue infections (SSTI)

Cellulitis

• Blood cultures if sepsis criteria are fulfilled
• Swabs (black) from any area of broken or blistered skin
• Aspirate from any blisters or bullae large enough to aspirate safely in a universal container (white) for microscopy and culture

Microscopy is not performed out-of-hours, any samples received over night will be processed the next morning.

Swabs are a less useful sample with a poorer diagnostic yield compared to tissue or pus in a universal container.

Necrotising fasciitis

• Blood cultures
• Tissue or pus in universal container (white) for microscopy and culture
• Swabs (black) from any area of broken or blistered skin

Bites – animal or human

• Swabs (black) from any area of broken or blistered skin
• Tissue or pus in universal container (white) for microscopy and culture

State clearly on the form that swab is from an infected human or animal bite.

Microscopy is not performed out-of-hours, any samples received over night will be processed the next morning.

Chronic wounds - vascular or diabetic ulcers, surgical sites

• Swab (black) after cleaning ulcer surface with tap or sterile water
• Tissue or pus in universal container (white) if debridement is undertaken

Do not swab chronic ulcers unless there is spreading cellulitis surrounding them, extending >2cm from the edge of the ulcer.

Do not swab the debris at the wound surface - always clean the surface first.

Suspected wound botulism in injecting drug users

• Serum (white top monovettes): At least 10ml. Serum samples must be collected before antitoxin is administered
• Pus: As much as possible in a sterile container
• If pus is not available, a swab of the lesion should be taken and put immediately into a transport medium for anaerobic culture
• Tissues: If surgical debridement is performed, tissues should be placed immediately into a sterile container

Confirmation of the clinical diagnosis is by the demonstration of botulinum toxin in blood samples or, in the case of wound botulism, by the identification of C. botulinum in wound specimens.

Routine laboratory tests are not helpful and specimens need to be sent to the reference laboratory. This can be arranged through the duty or on-call microbiologist.