Contact Plates – as mentioned are special Petri dishes which contain sterile growth medium prepared in a manner so the surface of the media protrudes above the rim of the plate. The contact plate is pressed against any flat surface the needs to be sampled. Any viable microorganisms on the surface will stick to the agar surface and will grow upon proper incubation. This technique reveals the number of viable microorganisms on a surface.
Swabs - are sterile and stored in a suitable sterile liquid. The swabs are rubbed over the test surface. The microbiologist can determine the type of microorganisms on the swab by subculturing it to media. Swabs are used for surfaces that are not flat, and can be used to sample hard to reach areas of machinery that could not be sampled with a contact plate. Swabbing is more qualitative than quantitative.
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