Unlike most infections ( for example a strep throat), where it is possible to determine the exact bacteria by doing a simple culture, it is not possible to simply take a culture from your nose to determine what the cause is of the sinus infections.
The bacteria inside the nose which we could theoretically culture are not the same as the bacteria growing in the sinuses unless you have previously had sinus surgery.
It is possible to take a culture from the drainage area of the sinuses, but this is something which typically must be done by a specialist using an endoscope.
The other way to determine which bacteria are in the sinuses is to insert a needle into the sinuses through the nose, obviously an invasive and potentially dangerous procedure which we would prefer not to do.
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A vaporizer for sinus treatment
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The non drug remedies for sinus infection