What it is (overview)

A Pus Culture and Sensitivity test (often called a wound culture or pus swab) is a laboratory test that looks for germs—most commonly bacteria—in pus or drainage from an infected wound, boil, or abscess. “Culture” means the lab tries to grow the organism from the sample so it can be identified (for example, Staphylococcus aureus), and “sensitivity” (also called antibiotic susceptibility testing) checks which antibiotics are most likely to work against that germ.

The test typically provides two key pieces of information:

• Culture result (what’s causing the infection): Identifies the bacteria (and sometimes yeast/fungi) present in the pus. If no organism grows, it may be reported as “no growth,” which can happen if antibiotics were started before the sample was taken, if the infection is caused by hard-to-grow organisms, or if the sample didn’t capture the infected material well.
• Sensitivity result (what treatment is likely to work): Lists antibiotics as “sensitive/susceptible” (likely effective), “intermediate” (may work at higher doses or in certain situations), or “resistant” (unlikely to work). This helps your clinician choose the best antibiotic and avoid unnecessary or ineffective medications.

This test is especially useful when an infection is not improving, is severe, keeps coming back, or when there is concern for resistant bacteria such as MRSA (methicillin-resistant Staphylococcus aureus), which is a common reason people search for MRSA screening in the setting of skin and soft tissue infections.

When & why it's usually done

Doctors most often order a pus culture and sensitivity when there are signs of an abscess infection or an infected wound and they need to confirm the cause and guide targeted treatment. It may be recommended if you have:

• Pus or drainage from a cut, surgical site, ulcer, or boil
• Redness, warmth, swelling, and increasing pain around a wound
• Fever, chills, or feeling unwell with a suspected skin/wound infection
• A painful lump that may be an abscess (often with a soft “pocket” of pus)
• Infection that isn’t improving after starting an antibiotic
• Recurrent boils or repeated skin infections
• Large, deep, or rapidly spreading infections (concern for serious soft tissue infection)

It is also commonly used in higher-risk situations where choosing the right antibiotic early is important, such as:

• Diabetes or poor circulation (higher risk of complicated wound infections, including diabetic foot infections)
• Weakened immune system (e.g., chemotherapy, long-term steroids, transplant recipients, HIV)
• Recent hospitalization, surgery, or medical devices (risk of resistant organisms)
• History or exposure to MRSA (household contacts, team sports, crowded living settings)

Depending on the location, the sample may be collected using a sterile swab (a “pus swab”) or by aspirating fluid with a needle. Whenever possible, collecting pus from deeper tissue or the abscess cavity (rather than surface drainage) can improve accuracy. Results often include an early report (preliminary growth) followed by a final identification and sensitivity panel after additional incubation.

Common diseases related to it

• Skin abscess (boil/furuncle) and carbuncle
• Cellulitis with draining wound or purulent infection
• Infected cuts, lacerations, and traumatic wounds
• Surgical site infection
• Diabetic foot infection and infected ulcers (pressure sores/venous ulcers)
• MRSA skin and soft tissue infection
• Infected cyst (e.g., infected sebaceous/epidermoid cyst)
• Animal or human bite wound infection

Health goals where it may help

• Finding the exact cause of a wound or abscess infection to support faster, more complete recovery
• Choosing the most effective antibiotic and reducing trial-and-error treatment
• Supporting antibiotic stewardship by avoiding unnecessary antibiotics and limiting resistance
• Reducing the risk of complications such as spreading infection, delayed wound healing, or recurrence
• Guiding care for high-risk wounds (e.g., diabetic foot ulcers, post-surgical wounds)
• Assessing for resistant bacteria such as MRSA in the context of recurrent or severe skin infections