Microscopy and Culture

To determine the cause of an infection, it may be necessary to grow body fluids and tissue samples in a laboratory. This is done in order to identify and assess bacteria and fungal infections.

When using microscopy, it is possible to find and identify micro-organisms and analyse samples to diagnose diseases in tissue samples.

When the sample arrives at the laboratory, it is spread out on a special gel, eg agar, in a plastic bowl (culture dish), which is then covered with a lid.

Extracts of live substances such as meat, bread or chocolate may be added to the gel in order to give it more nourishment. If the sample is thought to hold a particular bacterium, the gel can be mixed with specific substances that encourage the growth of this particular bacterium and suppress the growth of others.

The test is then placed in a heating cupboard at approximately 100ºF (about 35ºC) the temperature at which disease-causing bacteria thrive best. Often, several different bacteria will grow, but the one that causes the disease (the pathogen) will be dominant compared to the non-pathogen.

When do you need Microscopy and Culture?

Microscopy and culture is very useful to specifically identify an issue with your body. For example:

• The micro-organisms that cause sickness are separated into several different groups, according to their type. The most important are viruses, bacteria and chlamydia. Other groups include eggs and larvae from different parasites and protozoa.
• The standard way to identify bacteria is through using a culture (bacteria grown in the laboratory). In this process a non-contaminated group, which can be identified, is purified and assessed as a comparison.
• Fungi can also be grown and purified in the same way as bacteria, but this procedure is not often used.
• It is more difficult to analyse viruses and chlamydia, which require more advanced laboratory examinations. Some viruses and other micro-organisms are so difficult to culture that it is necessary to examine the person's blood (serum) for antibodies against the micro-organism.

Worms, larvae, eggs and protozoans are clearly visible under a microscope and can easily be identified by a trained microbiologist without further examination.

What are the Risks in Microscopy and Culture?

The biggest risk of microscopy and culture is not to the patient but to the laboratory technician.

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