Clinicians and microbiologists should follow proper procedures for collecting and handling wound swab specimens to obtain accurate microbiology results. Specimens should be collected prior to cleaning or antimicrobial treatment, using sterile collection methods. Swabs should be placed in transport media and containers sealed and transported promptly to the laboratory. Microbiologists should not receive specimens for acid-fast bacilli on swabs, as pus or tissue is preferred. Clinicians need to understand that positive cultures do not necessarily indicate infection, as opportunistic organisms may colonize wounds, and microbiology results depend on the quality of the specimen collected.

1. WHAT MICROBIOLOGISTS AND CLINICIANS SHOULD KNOW
ABOUT CULTURING WOUND SWABS
Dr.T.V.Rao MD
I am certain that we receive 10% of the swabs or discharges for culturing of wounds, the great
limitation is who collected, and how it is collected, because it certainly hampers the results, it is
most of the times entrusted to junior nursing staff or nursing students without much inputs on what
a hound is what is the anatomy of wound, however these matters to be addressed by the Infection
control committee,
Clinicians (including nurses, doctors and professionals allied to medicine) have responsibility for the
collection and safe transportation of samples to the laboratory. The validity of test results largely
depends on good practice in the “pre-test” stage and it is essential that documentation is accurate
and comprehensive (Higgins 1994).
ONE MUST FOLLOW THE INSTRUCTIONS AS
Use universal precautions for collecting and handling all specimens.
Obtain the specimen prior to any dressing or cleaning procedure of the wound. This will maximize
the material obtained and prevent killing of the organism by the use of antiseptics.
Use a sterile swab and gently rotate on the area to collect exudate from the wound and place into
transport medium. Where there is, pus collect as much as possible in a sterile syringe or sterile
container (do not use a swab) and send to the laboratory.
For detection of Mycobacterium tuberculosis, pus collected neat in to a pot or tissue biopsy is
preferred, however a calcium alginate swab can be used. The alginate swab gradually dissolves
maximizing the isolation of the organism as the number of organisms are usually small.
Whenever possible, collect all culture specimens prior to administration of any antimicrobial agents.
When collecting pus, specimens or impressions of wounds obtain as much material as possible as
this increases the chance of isolating micro-organisms which may be difficult to grow or are minimal
in number e.g. tuberculosis. Pus should be sent in a sterile specimen container, not on a swab
MICROBIOLOGISTS SHOULD NEVER RECEIVE THE SPECIMEN FOR ACID FAST BACILLI ON SWABS .
Specimens should be in tightly sealed, leak proof containers and transported in sealable, leak-proof
plastic bags. Specimens for TB should be double bagged. Specimens should not be externally
contaminated. Specimens grossly contaminated or compromised may be rejected.
Avoid contamination with indigenous flora. IT IS IMPORTANT IN WOUND SWABS as the surrounding
of the wounds are necrotic, we get the bacteria like pseudomonas may be just colonizers and may
not be true pathogens, and today many laboratories without quality controls report as drug resistant
pseudomonas, Proteus, Serratia Atypical Mycobacteria and many others and it is important make
some standard operating procedures, A positive wound culture does not confirm a wound infection.
Opportunistic microorganisms may colonize any wound. Wound exudate, which is naturally
bactericidal, inhibits the spread of surface contamination from becoming a deep wound infection.
However, when wound ischemia or systemic immune compromise supervenes, pathogenic
microorganisms propagate until an excessive concentration of bacteria in the wound precludes

2. healing. This heralds a true wound infection. Multidrug resistant organisms are becoming
increasingly common.
ALL ILL UNDERSTOOD COLONES TO BE STAINED AND MICROSCOPIC OBSERVATIONS TO BE MADE
BEFORE PROCESSING AS PATHOGENS
WHAT CLINICIANS TO UNDERSTAND FROM MICROBIOLOGY REPORTS
Microbiological tests are not as standardized as some other lab tests; the way in which a sample is
processed and the results are interpreted depend heavily on the information provided with the
specimen.
Please read more at
Ref Specimen collection - microbiology and virology The great Ormond street NHS Hospital for
children NHS foundation trust
Dr.T.V.Rao MD Freelance Clinical Microbiologist