Blood-Bronchus Barrier

Baby is a ten-years old mixed breed dog who weighs about twenty pounds.  She shares her home with two nice people, and two nice dogs, a six-years old Chihuahua and a sixteen-years old Chihuahua.  Baby’s owners had been taking her to another veterinarian for a chronic cough.  She had been coughing for over two months. In that time, she has been treated with five (count ’em, FIVE) different antibiotics without improvement.  They gave the antibiotic for a week, she didn’t get better, they went back and got another one. She seemed to do a little better when she received a cortisone shot along with one of the antibiotic treatments, but when it wore off, she was coughing as badly as ever.  They finally decided they would like a second opinion.

Her chest didn’t sound bad with the stethoscope and her throat looked okay.  There were no swollen lymph nodes. Temperature was normal, as was her blood count.  Time for antibiotic number six? Probably not.  Chest X-rays didn’t show any lung congestion.  It seems that she has disease in her small airways, the bronchioles.  Maybe there’s something in the home causing some sort of allergic inflammation. After all, the only time she really got any better was with the cortisone, and her two house-mates haven’t been coughing at all.  It seemed logical, but cortisone and cough suppressants didn’t help much.  A bronchodilator to open up those little airways didn’t help much either.

Fortunately (?) there was a new development in the case: both house-mates began coughing, too.    Now, with a chronic cough that could be caused by an infection, that hasn’t responded to five different antibiotic treatments, you’d really like to hit the right medicine this time.  So how are you going to do that?  With a trans-tracheal wash, that’s how.  Under light anesthesia, we use a brand-new sterile endotracheal tube to keep the windpipe open. Then we pass a sterile tube about the size of a pencil lead through that, and all the way down deep into the airways.  A small amount of sterile saline solution is flushed in and sucked back out again.  The recovered fluid, plus any bonus phlegm, should represent what’s going on deep down in those airways.  Since anesthesia is required, we picked the six-year old housemate for our subject, since they are ALL coughing now, and she’s the youngest and healthiest of the three.

The clinical pathologist looked at the glop under the microscope and didn’t see any bacteria and no infection-fighting cells to speak of.  She thought it was some kind of allergic reaction.  Ah, but when the culture came back, there was a heavy growth of Bordetella, the germ commonly associated with the "kennel cough" syndrome. Whaddayaknow? It was an infection all the time.

Now here’s the weird thing.  When the laboratory grows our germ, they also test it to see which antibiotics will kill the nasty little rascals.  Oddly enough, this Bordetella gets a report card that says all five medicines Baby received should kill it dead.  Only the whole (dog) family’s coughing.  Why didn’t Baby get well?  Why is she still coughing and finally managed to give the germ to everybody?

It’s like this:  the medicine dissolves in the stomach, gets absorbed into the bloodstream, diffuses into the body cells, goes all over…almost.  There is some kind of a barrier between the bloodstream and certain organs: the brain, the prostate, and the cells that line the bronchial tubes.  The medicine doesn’t get from the bloodstream into the mucus and crud that lines those airways.  This is why five different kinds of antibiotic pills didn’t work.  The bacteria just laugh and keep on trucking.

They’re not laughing now, though.  We are using a nebulizer to make the antibiotic into a mist that the dogs breathe right on down into their airways.  Antibiotic rain on a microscopic scale will be hitting those germs like acid rain on a national monument. They will be toast…or soup, or something.  They will die, and the dogs will get well.  Now we do the laughing.

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