MRSA update

Much to my surprise, I arrived at work this morning to find a fax from our local reference lab. It is entitled "IDEXX Continues to Identify Methicillin-Resistant Staphylococci on Routine Cultures and Offers MRSA Screen for Healthy Pets."

Now, I think that screening on healthy pets is more a marketing issue based on a suspicion, but I can't argue their reasons. Here's a couple of excerpts that are interesting:

"...a recent study in a tertiary referral center revealed that 35% of S. aureus isolates, 17% of S. intermedius isolates and 40% of S. schleiferi isolates in dogs and cats were methicillin resistant..."

"A follow-up study collected cultures from 50 healthy dogs and 59 dogs with inflammatory skin disease. MR staphylococci were isolated from 4% of clinically healthy dogs and 10% with inflammatory skin disease."

"Symptomatic MRSA infections in veterinary patients are rare and, in most cases, suspected to be the result of reverse zoonosis from infected humans."

In other words, MRSA is becoming more common in veterinary patients, ESPECIALLY those treated for chronic wounds, lung infections, bone infectious, and chronic skin disease. Most importantly, this means that all of these infections are going to be resistant to about two thirds of the drugs I have on the shelf.

This also means that I need to be much more careful handling my patients with suspicious infections. Veterinarians are REALLY bad about not wearing gloves and protecting ourselves. I wash my hands all the time, but don't usually wear gloves. YUCK. Guess I should buy a box of gloves before some poor dog infects me with the funk their owner gave them.

AMH

MRSA or "The Bad Staph"

MRSA or (MERSA) or resistant staph are all terms used to describe a particular form of a bacteria named Staphylococcus aureus. We are all covered in staph organism. It's common. It's usually harmless. However, the concern for these MRSA or methicillin-resistant Staphylococcus Aureus is that these particular bacteria appear to be fairly aggressive and highly resistant to antimicrobials. Every year this population of bacteria seem to become more adaptive and develop new resistance remarkably fast.

It is estimated that up to 25% of people have some kind of MRSA currently residing on their body. This isn't a big deal until the bacteria gains access through a wound or has an opportunity to grow in a sinus infection, at which time it can become a wicked problem to deal with. I have, in fact, had a MRSA cultured from my nose a couple of years ago. Ironically enough, it was resistant to the sexy antibiotics and sensitive to the really cheap, easy antibiotics and we appear to have cleared up up without any problems. Total cost of prescription: probably $0.50.

On the flip side, MRSA kills thousands every year. Why the difference? Individual quirks in a patient's immune system, regional strains of bacteria, or types of wounds for one reason. Some individuals end up spending thousands of dollars on cool, sexy antibiotics compared to my rather plain $0.50 treatment.

I bring these bacteria up, because I have been asked if a dog or cat can either 1) get or 2) give a MRSA to the human in the household. Interestingly enough, the answer is YES to number one and maybe to number two.

There have been a few studies looking a cultures submitted to veterinary labs where a staph aureus has been cultured. The type of staph cultured from dogs and cats is usually staph intermedius. They are usually easy to kill, but not always. As it turns out, there have been S. aureus cultured and when those were checked, some were actually MRSA. This was a pretty scary finding.

You can actually check the genetics and determine that the MRSAs cultured were probably of human origin. When multiple people in a household continue to culture positive for a MRSA, it might be appropriate to screen the pets in the household as well. The current guidelines from the CDC do not recommend routine screening of pets or people unless there are households with severely immunocompromised (Chemotherapy, AIDS, transplant patients, etc) and there have been problems with MRSA. In those cases, every mammal in the household should be screened (people, dogs, cats, rabbits, etc).

Short version - Dogs and cats can apparently grow MRSA organism as part of their normal flora. These probably came from the people in the house. They might be able to pass it back and forth between pets and people. Don't worry about this unless you have a situation where your physician is trying to locate a potential source of re-infection or if you are immunosuppressed.

WHEN YOU ARE PRESCRIBED AN ANTIBIOTIC FOR YOU OR YOUR PET - FINISH THE ENTIRE TREATMENT. DO NOT STOP EARLY. Appropriate treatment with the right antibiotic at the right dose and for the RIGHT LENGTH of time is the main way to fight development of resistance in bacteria. Both human physicians and veterinarians are to blame on this one. Please, please, please follow the instructions on the label.

AMH