Tuesday, April 27, 2010

Bacterial Alphabet Soup

There has been a fair amount in the press recently about antibiotic resistant super bacteria that are going to end the world. TV, print, Internet, all talking about MRSA, MRSI, MRSP, and even the dreaded flesh eating bacteria, I think that I will skip the horrid flesh eating bacteria for now, as it is mostly a human disease problem and the pictures would be far to gruesome for this blog. If you have a genuine interest or just want to see gross pictures, you can follow the link here.

Let's start with MRSA. I'll translate, first from alphabet to medicalese, to English. French translation will require a different author. The initials stand for Methecillin Resistant Staph. Aureus. Staph. Aureus is a round (cocci) bacteria commonly found on the skin. While we used to think that all of these potentially disease causing cocci were Staph aureus, it turns out that this is a pathogen of people and other species have there own species of Staph. Here is group of Staph as seen under the microscope, a Staph meeting as it were.

The M is for methecillan, an antibiotic and the R is for resistant. MRSA is resistant to, that is not killed by methecillin or any penicillin type antibiotic. The problem is that many of these bacteria also develope multi drug resistance, that is that many antibiotics will not affect them. As you can see this can cause a big problem.

MRSA has become a huge source of complications in human hospitals as this is a place were there are alot of sick people, and bacteria, and antibioitics to stimulate resistance. (We can talk about how bacteria become resistant in another post if anyone comments and is interested)

Dogs can get colonized by MRSA. They get it from their owners and it might not ever cause a problem. However, if they should have some weakening in their immune system, allowing these bugs to get a foothold, then we can have a problem. At our practice, we have seen several cases of MRSA recently. In each case we were able to trace the source of infection back to an owner that had been treated in some sort of health care facitlity.

What about the other intitials you ask? Well, as I alluded to earlier, other species of animals have there own staph bacteria. In dogs they were reclassified as Staph. intermedious (SI) and most recently, Staph. pseudintermedious. Here is a picture of staph, closer up. Can you tell what species it is? No one can just by looking. Special tests are needed.

In fact, you can't tell if this is a resistant staph or just a plain old staph just by looking at a photo micrograph. Sensitivity to antibiotics is determined by doing cultures and sensitivities in the clinical path lab. We have seen an increase in the number of MRSP infections in our practice over the last few months. I'm not sure if that is because more of our staph infections are resistant to methecillin, or if we are just more aware and doing more cultures. These animal staphs can colonize people and cause diseae if the opportunity arises.

Now, were do we see most of these resistant staph infections in our animal patients? The number one location is in the ear. That is why your veterinarian should not just look at an ear like this and send you home with anti biotics.

Or even worse, just take a phone call from you and dispense antibiotics without a thorough examination. We do a cytology exam on all ear infections. (look under the micrscope to see if there are bacteria present). If there are bacteria, we do a culture and sensitivity so that we can prescribe the best medication to cure the infection. Then we set up a maintenence program to prevent future infections. The indescriminant use of antibiotics is one cause of the increased incidence of resistant infections. You need to wash your hands after treating infections so that you don't pick up these bacteria and have them growing in you waiting to cause disease.

Here is the other very common location for bacterial infection, the skin. People often mistake this type of lesion as ringworm (another topic for another day) but this is a classic presentation for a staph infection in a dog. These also need to be treated with appropriate antibiotics, both topical and systemic.
Now what can we do to prevent the spread of bacterial diseases from patient to care giver, owner to pet, and pet to owner?

WASH YOUR HANDS!! Do it frequently and do it well. Use antibacterial soap. Use the hand sanitizer stations that popped up during the swine flu scare. These will kill bacteria as well as flu viruses.

Keith Niesenbaum, VMD
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