Guidelines for Ordering Skin and Soft‑Tissue Cultures

Specimen Selection and Collection Technique

The Infectious Diseases Society of America recommends that tissue, fluid, or aspirate specimens should be collected whenever possible to optimize pathogen recovery and avoid contamination, as swabs are not the specimen of choice for anaerobic or aerobic cultures 5, 6
The preferred specimens for collection, in order of preference, are aspirates of fluid or abscess contents, tissue biopsies or curettage, surgical specimens, and swabs, with swabs being used only when aspirates or tissue cannot be obtained 5, 7, 8, 9, 10
When swabs must be used, flock swabs should be used as they optimize specimen collection and minimize entrapment, and the swab should be saturated thoroughly with sampled fluid to ensure adequate material 10, 11, 12

The Infectious Diseases Society of America recommends that the wound should be thoroughly cleansed and debrided before specimen collection to avoid contamination with surface colonizers and normal flora 7, 8
Debridement removes necrotic tissue and allows access to deeper infected material, and proper cleansing minimizes contamination with normal skin or mucosal flora 5, 6, 7

The Infectious Diseases Society of America recommends that specimens for anaerobic cultures should be placed immediately into anaerobic transport containers to support recovery of anaerobic bacteria, and transported at room temperature, delivering to the laboratory within 2 hours for optimal results 5, 6, 10, 11
For aerobic-only cultures, sterile containers should be used for tissue/fluid specimens, and swab transport devices for swabs, with transport at room temperature and delivery within 2 hours 10, 11

The Infectious Diseases Society of America recommends that a Gram stain should always be requested with anaerobic cultures, as it evaluates specimen adequacy, provides early presumptive diagnosis, and identifies mixed aerobic-anaerobic infections 5, 6, 13

For head and neck soft tissue infections, aspirate or biopsy should be collected while avoiding mucosal flora contamination, using anaerobic transport for odontogenic infections, and keeping tissue specimens moist during transport 5, 6
For diabetic foot infections, the wound should be debrided thoroughly before specimen collection, with tissue obtained from the debrided base by curettage or biopsy, and cultures required for moderate/severe infections but may be unnecessary for mild infections in antibiotic-naive patients 7, 14
For blood cultures, at least two sets (60 mL total) should be collected from different anatomical sites, including both aerobic and anaerobic bottles in each set, with proper filling of bottles (10 mL per bottle) 15