if your dog ever has to have a tracheal wash:

[davet]

here is what it is, Via Valeri C. Devaney, DVM
First of all, let me give a brief explanation of a trans-tracheal wash for those who aren't familiar with it.

In a trans-tracheal wash, a tube is placed into the large airway, called the trachea (either using an endoscope, or inserted through a small surgical incision over the throat). A small amount of sterile fluid is introduced into the trachea, and then promptly removed again. This fluid, which has washed around in the trachea, has picked up mucous and germs. The fluid can then be sent to a lab to grow the germs in a culture, which allows us to identify the specific bacteria and which antibiotics work to kill it. A trans-tracheal wash is often called a "trach wash" (pronounced trake, like rake), or abbreviated TTW.

The reason to use a trans-tracheal wash is for an infection in the lungs, so that you can know the exact bacteria you are fighting and what will work to kill them. There are other procedures (generally, broncho-alveolar lavage, or BAL), which can also be used. In fact, in a large dog with aspiration pneumonia (because you have a localized infection you may be able to reach specifically with the endoscope), a BAL may be a much more accurate procedure to use, because it does the same thing as a TTW, but further down in a section of affected lung.

In dogs that have been on antibiotics, the antibiotics can reduce the growth of germs, and make it difficult to get enough germs on your TTW to grow anything. Usually if it has been 24 hours since a dose of antibiotics (if the antibiotics are normally given more than once a day or 36 to 48 hours after once-daily dosed antibiotics), then bacteria have a chance to flourish enough to get a good sample.
However, in the case of a patient which has an infection against which the antibiotics are definitely not working (a resistant infection), there may be plenty of the important bacteria (the resistant ones) present even when on the antibiotics.

A trans-tracheal wash can also pick up "normal" germs because the trachea (especially when you do a procedure on it), may have a small number of "normal" or "opportunistic" bacteria that are not really involved in the infection.

Does that answer your question?