Bacterial Culture Test

Last updated: 24 November 2017

What is a bacterial culture?

A bacterial culture is a test used to determine whether bacteria or fungi are infecting a wound.

Bacterial cultures are typically collected from infected (or potentially infected) tissue, but can also be taken from:

  • Body fluids (blood, urine, sputum, pus)
  • Ears
  • Eyes
  • Nails
  • Hair

How is a bacterial culture performed?

A sterile swab is taken from any area of the body that appears to have an infection.

  • Body fluids may be collected into a suitable sterile container.  
  • Alternatively a cotton-wool swab, which is like an ear-bud, is used to collect a small amount of fluid from a wound or surface. 
  • Some of this sample may then be transferred onto a glass slide at the bedside, for microscopy.

The sample is then placed into a special medium that encourages growth of bacteria.

The microbiology lab then attempt to culture (grow) a wide range of organisms (especially bacteria) from this sample, to determine which organism is causing the infection. It may take 2 to 3 days to actually culture the relevant bacterium in the laboratory.

Finally, small amounts of antibiotics are then applied to determine which antibiotics are most likely to be effective in treating the infection (called the antibiotic sensitivity).

When would you need a baterial culture?

Some of the reason you would need a bacterial culture are:

  • To diagnose the cause of your infection or suspected infection
  • To identify the best way to treat your infection

Symptoms of infection include pain, swelling, warmth, redness and fever.

Test results, explained

A negative culture or ‘no growth’ does not necessarily exclude infection, but is relatively reassuring.

An organism may initially be identified by its general group, such as gram-negative bacillus, and then subsequently identified more accurately as E coli.

One or two days later the report will often contain the antibiotic sensitivities as a list of antibiotics with one of the following next to each drug:

  • R (resistant)
  • S (sensitive)

This reflects the sensitivity of the organism to the antibiotic in the laboratory dish, ‘in vitro’. This may not always be exactly the same as the clinically observed sensitivity in the human body, ‘in vivo’, in real life.

Next steps

Related specialists

Related procedures

  • Blood Test (venesection)
  • Urinary Catheterisation
  • Suprapubic Aspiration
  • Tissue Biopsy
  • Bronchoscopy
  • Joint aspiration
  • Lumbar puncture

Related tests

  • Viral Cultures
  • Blood Cultures

Also known as

  • Micrsocopy, Culture and Sensitivity (MC&S or MCS)
  • Wound Swab

 

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This article is for informational purposes only and should not be taken as medical advice. If in doubt, HealthEngine recommends consulting with a registered health practitioner.