Tuesday, February 15, 2011

The antibiotic war

If you read the newspaper or watch the news at all, then you've likely heard about the problem of antibiotic resistance. Bacteria are nasty little boogers in that once exposed to an antibiotic, they like to evolve to become resistant to that particular drug. There are many, many ways that bacteria can do this, and it is leading to big problems in human medicine. Drugs that once worked miracles (such as penicillin) now only work for very selected problems. We are having to rely more and more on "big-gun antibiotics" to clear infections. Eventually, we may run out of antibiotics altogether.

Reasons for this resistance include over-prescribing of antibiotics to patients that do not have a documented bacterial infection, patients not taking the antibiotics for the full-course but instead stopping when they feel better (and selecting for resistant bacteria), and prescribing of the wrong antibiotic for the bacteria involved. All of these lead to bacterial resistance and are bad news for us.

As a result, doctors are trying collectively to be more responsible with antibiotics so that we don't run out of them. After all, we need them to treat so many terrible bacterial infections.

The same is occurring in veterinary medicine. Some are leading the way for all. And we're still not doing good enough. Antibiotics are the back-up, default treatment for a variety of conditions. It's a knee jerk reaction when we as veterinarians don't understand what's going on. Why not try a course of antibiotics? It can't hurt, right?

The truth is that it can! Animals are starting to have resistant infections, too. As people have MRSA (methicillin resistant staphylococcus aureus), dogs and cats are now coming down with MRSI (methicillin resistant staphylococcus intermedius). I saw it numerous times during my internship. The same causes are present: over-prescribing of antibiotics, inappropriate dosing schedules, and the wrong antibiotic for the bacteria.

What can we do about this? Veterinarians need to step up to the challenge and really start thinking before we prescribe antibiotics. This sounds simple, but it is very, very challenging. Many owners come into the veterinary hospital asking for antibiotics. Many veterinarians think, why not try them? They're cheap and often we are faced with clients who refuse to let us do any diagnostic testing for financial reasons, thus we are left "shot-gunning" treatment as best we can. Further, owners will frequently get mad when they are NOT given antibiotics, even though they don't really understand why they need/want them in the first place.

It is our place as veterinarians to understand when "shot-gun" therapy is appropriate and when it is not. It is our place to tell our clients "no, more testing is needed before therapy can begin", and it is our place to understand when we are contributing to the problem and not helping.

Here is a list of diseases in which I think antibiotics are over-used and contribute to resistance (these are my opinion, of course. Gleaned from schooling, my internship, and VIN -but still, my opinion).

1) Cat bite abscesses: this is an incredibly common presentation in both ER and GP. A cat comes in with a big, pus draining abscess somewhere on the body. It is very likely the result of another cat bite. The cats usually have a high fever (103-105), are lethargic, and don't want to eat. Most veterinarians either prescribe oral antibiotics or give a shot of Convenia, a long-acting antibiotic. The problem? Once the abscess is open and draining, the infection is leaving the body. Antibiotics are not warranted. I stopped treating cat bite abscesses with antibiotics after my cat, Boo, got outside and developed a giant one himself. 2 doses of clindamycin, and he started vomiting all over my house. After thinking through the process of abscess formation and doing some reading on VIN, I stopped the antibiotics, gave him fluids under the skin to bring his fever down and hydrate him, drained and flushed the abscess, and waited. Three days later, he was good as new. Since then, I have stopped treating cats with these abscesses with antibiotics. They get well just as fast in my experience. (The same is true with horses and strangles - an abscessation of the lymph nodes in the neck - once open and draining, antibiotics are no longer used because they select for resistant bacteria while adding nothing to treatment). I'm not using my n=1 case of Boo to back this up, but thoughtful, careful research on abscesses, how they form, and the like.

2) Pancreatitis: as discussed in my last post, pancreatitis has historically been treated (in dogs) with antibiotics. Recent literature has demonstrated that >95% of pancreatitis cases are inflammatory but not infectious. Thus, antibiotics do not help with recovery. I no longer treat my uncomplicated pancreatitis cases with antibiotics. If they develop abdominal effusion (fluid in the abdomen) or other signs of systemic disease, they are started on broad spectrum antibiotics. Cats are different. They have shown to often have a bacterial infection related to pancreatitis, and if pancreatitis is suspected, they should be on specific antibiotics.

3) GI surgery: this is a knee-jerk reaction of veterinarians, as well. If we have to cut into the stomach or small intestines, antibiotics MUST be warranted for at least a week, right? WRONG. In a patient undergoing GI surgery, as long as no peritonitis (inflammation of the abdominal cavity, usually manifested by free fluid in the abdomen) is present prior to surgery, antibiotics should only be used peri-operatively - meaning at induction of anesthesia and 90 minutes into surgery. Afterwards, they should be discontinued. If they are used, and the patient has a failure of the surgical site after surgery (the sutures come loose and start leaking), inappropriate antibiotic administration can mask the signs of sepsis until the patient is severely compromised. I learned this recently at a conference, as well as at the specialty/referral hospital where I sometimes do relief work. I was shocked, but as I thought through it and did some reading, I came to realize that it makes sense.

4) Cats between 1-10 years with bloody urine/straining: it is very rare for a cat between the ages of 1 and 10 years old to have a true urinary tract infection. It is much more common for them to have a condition called FLUTD/idiopathic cystitis. This condition, like pancreatitis, is not infectious but inflammatory. Antibiotics often appear to help, as the condition naturally runs its course in 3-5 days. Thus, for many years, antibiotics were prescribed. It is realized now that this condition is extremely rarely bacterial in nature (unless the cat is older than 10 years) and antibiotics are not warranted. If your veterinarian suspects a UTI, a culture - either in-house or sent out to a laboratory - to confirm this should be submitted. This will identify if bacteria are present, WHAT bacteria are present, and WHICH antibiotic should be used.

5) Vomiting and diarrhea: many owners come in with a dog that has vomiting and diarrhea. They decline all tests (bloodwork, xrays, etc). The veterinarian tries to cover all bases and prescribes a round of antibiotics - frequently Clavamox (amoxicillin that has special anti-bacterial properties). The problem with this? So many v/d cases are not bacterial in nature. They are often related to getting into the trash, eating a toy and having it stuck, or just run-of-the-mill gastroenteritis. Antibiotics are not warranted in any of those cases. Time, anti-emetic therapy, SQ fluids, and nursing will usually help these diseases run their course (an exception to this is metronidazole. Metronidazole is an antibiotic with unique anti-inflammatory properties in the large intestine. As a result, it can help significantly with diarrhea. The dose for this is much, much lower than the antibiotic dose at 7.5mg/kg.)

6) Trauma: I cannot tell you how many patients I've seen on antibiotics that were just hit-by-a-car and have only the most minor road rash or skin abrasions. Again, it's a knee-jerk reaction with little basis. How many times have you scraped yourself on concrete, barked your shin, or cut yourself in the kitchen? How many times were you on antibiotics for that? Trauma alone is not an indication for antibiotics unless severe or contaminated lacerations are present.

7) HGE (hemorrhagic gastroenteritis): this condition is also not likely bacterial in nature. I do tend to put my cases on the low-dose/anti-inflammatory metronidazole dose to help with the large intestine inflammation (7.5mg/kg), but otherwise - fluid therapy is the mainstay of treatment.

8) Kennel cough/Bordatella of dogs and feline upper respiratory tract infection: these are common respiratory diseases of cats and dogs that are almost always caused by viral infections. Antibiotics are very rarely warranted, and I never use them. Dogs usually respond well to rest and an anti-tussive such as butorphanol. Cats do well with home nebulization, warmed, foul-smelling, wet cat foods (when cats can't smell, they can't identify food), and SQ fluids to help maintain hydration. In rare cases, these upper respiratory tract infections can move into the lungs and cause pneumonia, at which point, antibiotics are ABSOLUTELY indicated - but as I said, this is rare. Cats can be a little tricky in that some can develop chronic upper respiratory tract infection that does respond to a short-course of antibiotics and steroids, but this shouldn't be the default treatment. In my limited experience, some small kittens with URT infection respond well to Clavamox, too. This might be because they are young, have incompetent immune systems, and have secondary bacterial infections too.

So, there you have some common conditions that are frequently, inappropriately treated with antibiotics. Remember, antibiotics are not benign - they can cause GI upset with vomiting, diarrhea, and appetite loss, and some have been linked to pancreatitis (such as sulfa drugs). On top of that, over-use has lead to antibiotic resistance, a very serious problem for MDs and veterinarians alike.

The moral of the story: think carefully before you accept antibiotics from your veterinarian. Read up on the condition that your pet has been diagnosed with, make sure you are familiar with the indications for antibiotic therapy. Veterinarians and veterinary students: really ask yourself if antibiotics are warranted, or if they are making you (and the owner) feel better. We live in a litigious society. We are frequently faced with clients that tie our hands diagnostically and therapeutically. Still, we are the guardians of both animal AND human health, so we have a strong responsibility to be responsible with the medications we have. I remind myself of that every day.


Anonymous said...

Loved this post. As soon as I began reading, I immediately thought of kennel cough and FLUTD as fitting the bill for over-prescription of antibiotics, but I didn't know about the others you mentioned.

I also thought that it might be beneficial in the future to post something about how to identify and critique research articles. This would help clients as well as those in the veterinary field scrutinize the information they find online.

"We are frequently faced with clients that tie our hands diagnostically and therapeutically." --Amen! Well-put!

Learning said...

Totally agree! Another great post. I'm not sure if I'm brave enough to skip antibiotics for cat-bite abscesses...but that's what I said about giving up antibiotics post-prophy in severe perio disease and I got over that pretty quickly (ie I don't use them any more following MOST perio therapy procedures). I will give it some more thought and try to let the next one heal with the simple principles of flushing and wound healing!

Nicki said...

Good post. I have only worked for older practioners and i have a terrible time convincing clients (and staff) that their cat does not have a bacterial UTI.

Curious Cat said...

Can you say some more about perioperative abx? I'm a little confused about how this is an exception to the general principle of risks/benefits of single doses of abx and prophylactic abx. Intuitively, I can come up with a few thoughts but I'd love to hear what you have to say! :-)

The Homeless Parrot said...

So, the way I choose peri-operative antibiotics is according to current recommendations. If you are interested in references: both the Slatter and Fossum surgery textbooks devote a large chapter to this section.

First, classify the surgery type.
1) clean
2) clean-contaminated
3) contaminated
4) dirty

When entering a hollow viscus in a patient WITHOUT evidence of peritonitis or systemic compromise at the time of surgery, this is considered a clean-contaminated surgery.

If gastric or SI, cefazolin or another similar abx is good (ampicillin, Unasyn, etc).

If you enter the colon, a broader spectrum (such as "BAM" - baytril, ampicillin, metronidazole) is likely called for.

These should be administered about 30 mins prior to the 1st surgical incision. For us and most others, this is done at induction. This allows the abx to reach good levels at the surgery site prior to surgery.

If surgery is less than 90 minutes long, another dose is unneeded. If >90 min, another dose should be given.

After that, as long as there was no gross abdominal contamination, abx should be discontinued.

The point is that it gives you coverage while doing surgery and releasing bacteria, but you are not unnecessarily using abx once you are out of surgery.

These are the current recommendations.

The Homeless Parrot said...

Another time you might continue abx in a clean/clean contaminated surgery is in patients with immunocompromise, etc (diabetics, for example).

Curious Cat said...

Makes sense. Thank you!

Chris Bern, DVM said...

Good points all around. I would disagree on only two parts. I do think that antibiotics are warranted for most cat bite infections, as there can be infection deeper in the tissues than may be obvious, and the abscess can return. I've seen several that will open, drain, heal over, and then re-form. This can go on repeatedly until antibiotics are used.

I also think that many times antibiotics are indicated with upper respiratory infections or tracheitis in dogs, as Bordetella is a bacterial infection. Now admittedly we don't normally do tracheal washes to confirm it, but I'd rather use something to treat a likely infection in the early stages before it turns in to pneumonia.

Other than that I completely agree with your points. Too many people over-use antibiotics when the are not indicated. Just recently we treated a FLUTD case simply by putting it on a canned urinary diet. The urinalysis didn't show signs of infection, so we avoided antibiotics. I've also surprised clients because I never use these medications "just in case", especially if there are limited to no signs of infection.