Pressure Ulcer Colonization and Infection


All open wounds have bacteria. The amount of bacteria can be minimized through adequate cleaning of the wound, absorption of drainage and debridement if necessary.

Odor often indicates a need for change in cleaning frequency, change in dressing to increase absorption, or debridement.


Use of topical antibiotic creams is controversial. Some clinicians believe they are effective in the short term especially if the wound is heavily exudative.


Use of infection control measures should be standard with any open wound


Wound Infection

All chronic wounds are colonized with microorganism. When the bacteria overwhelms the host, infection occurs. The diagnosis of wound infection is based on the clinical signs and symptoms of the patient, and culture and colony count Colony counts higher than 100,000 (10x5) are considered indicative of infection.
of the wound.

Local Signs of Infection

Erythema or skin discoloration




Increased pain

Purulent wound exudate with or without foul odor


Systemic Signs of Infection

Elevated temperature

Elevated white blood cell count

Confusion or agitation in older adults

Red streaks from wound

A tissue biopsy, needle aspiration or a quantitative swab technique are the most frequently used methods to determine bacteria counts in wound tissue. They can detect aerobic and anaerobic organisms.

Quantitative Swab Technique

! This technique has been criticized as a method that produces information about colonization of the wound surface rather than in tissue infection.


Cleanse wound with a non antiseptic solution

Rotate a sterile cotton-tipped applicator stick in a -2  cm area of open wound for 5 seconds

Apply pressure to swab tip in the sterile tube and transport to lab

Lab results are expressed as organisms per swab or CFU per swab or in a semiquantitative manner, such as scant, small, moderate, large (1+-4+) bacterial growths

Needle Aspiration

Use 10cc syringe with a 22-gauge needle

Insert needle through intact skin

Withdraw the plunge to the 10 ml mark

Move the needle backward and forward at different angles for 2-4 explorations

Return the plunge gently back to the 0.5 ml mark and withdraw the needle.

Transport the specimen to the laboratory

Data are expressed in colony-forming units (CFU) per volume of fluid

Tissue Biopsy

Remove a piece (3-4mm) of tissue by dermal punch biopsy or a scalpel

Clean area with sterile solution, no aseptic

Perform tissue biopsy and apply pressure to area to control bleeding

Promptly transport biopsy tissue to laboratory

Tissue findings are expressed in number of organisms per gram of tissue