At a glance
Also known as
Aerobic wound culture; Anaerobic wound culture
Why get tested?
To detect a bacterial wound infection, to determine which clinically significant are present, and to isolate and grow the bacteria for subsequent susceptibility testing.
When to get tested?
When the doctor suspects that your wound is infected by a .
A sterile swab used to collect cells or from the site of the suspected infection; may also include aspirations of fluid from deeper wounds into a syringe and/or a tissue .
Test preparation needed?
What is being tested?
A bacterial wound culture is a test that is used to detect and identify in a potentially infected wound. Wounds may be superficial breaks in the skin such as scrapes, cuts and scratches or may involve deeper tissues such as incisions, bites, punctures or burns. Any wound may become infected with a variety of bacteria. A culture helps to determine when a wound has become infected with specific types of bacteria, and which antibiotic would best treat the infection to aid wound healing.
A culture is performed by collecting a sample of fluid, cells or tissue from the wound and placing it on or in appropriate . The media encourages the growth of bacteria that may be present, allowing for further testing and identification. Often in a sample from a wound infection there will be either a pure culture of a pathogenic (only one kind will be found) or one type will predominate within a mixture of organisms. In some cases, such as with a human or animal bite, there may be several present.
Wounds may harbor different types of organisms that have different requirements for growth. These organisms may be somewhat predictable from the site of infection so specific growth requirements from different specimen types are catered for within the laboratory. Some bacteria infecting a wound may require air for growth () while some require a no-oxygen or reduced-oxygen environment ( or ). Moreover, some bacteria may need specialised nutrient factors to grow adequately (fastidious organisms). Care must be taken when handling the samples so that their growth is encouraged and the probability of their detection and identification are optimized.
The next step in the process is to identify the different types of microorganisms present. Conventionally, identification is a step-by-step process that may involve many tests and evaluations performed on the sample before it is cultured or on the bacteria found growing in the culture. One such test is the Gram stain. It involves placing sample or smearing individual colony types onto a glass slide and treating the slide with a special stain. Under the microscope, the bacteria can be classified into Gram-positive and Gram-negative organisms and by shape into cocci (spheres) or bacilli (rods). With this information and additional biochemical tests, the types of bacteria present can be identified. Nowadays, mass spectrometry is used as a one step process to identify the different bacteria present in a wound sample once it is cultured. Mass spectrometry using matrix assisted laser desorption ionization time of flight (MALDI-TOF) can provide an identificationi to the genus and species level in less than an hour. This technique significantly decreases the time needed to identify bacteria from traditional biochemical reactions that require overnight incubation.
For many of the pathogens identified in the wound culture, antimicrobial susceptibility testing is required to guide treatment and to determine whether the strain of bacteria present is likely to respond to specific antibiotics. In order to do this a pure culture (isolate) of the identified bacteria must be available. This may require additional time in the laboratory to separate and identify each clinically significant bacterial species.
The wound culture, Gram stain, and susceptibility testing all contribute to inform the doctor which pathogen(s) is present and what antibiotic therapy is likely to inhibit its growth.
How is the sample collected for testing?
A sterile swab may be used to collect cells or from a superficial wound site. From deeper wounds, aspirations of fluid into a syringe and/or a tissue are the optimal specimens to allow for the recovery of and bacteria.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.