Drug Resistant Staph Infections In Pets

Superbug bites dog
Drug resistant staph infections aren't just for humans anymore
By Christie Keith, Special to SF Gate
Tuesday, May 28, 2008

There's a new and growing threat to your pets' health, and while I wish I could tell you it's just another Internet rumor, it's all too real. I should know, because my dog is its latest poster child. I'm talking about something you might have thought only affected humans: drug-resistant staph infections.

We hear a lot about these types of infections in people these days, severe ones spread in hospitals and less severe ones spread in daycare centers, schools and gyms. Most human infections involve methicillin resistant Staphylococcus aureus, or MRSA. In dogs and cats, the bacteria is slightly different — methicillin-resistant staphylococcus intermedius, or MRSI — but it's otherwise pretty much the same problem: some strains of a common bacteria found in and on most dogs, people and surfaces have evolved to resist the antibiotics we normally use to treat it.

My introduction to MRSI began three months ago, when I noticed my 9-year-old borzoi, Kyrie, had a small, quarter-sized red patch on her hip that seemed to hurt her terribly. I got her into the vet the next day, and she diagnosed a spider bite, shaved and cleaned the area, and put her on antibiotics, pain medication and a topical lidocaine spray to numb the wound. She predicted Kyrie would feel better in around 48 hours.

But Kyrie spent the night restless and whimpering despite the pain medication. And the next day, her coin-sized sore had become 8-by-8 inches of infected, oozing, red, raw skin. Unable to sleep while she was so uncomfortable, I spent a few hours on the Internet, where I learned two things. One, there are no venomous spiders in San Francisco, where we live, and two, most diagnosed spider bites are really something else entirely: drug resistant staph infections.

I took Kyrie to a specialist in the morning, and she agreed that her sore was almost certainly caused by MRSI. She put her on a different, hopefully more effective antibiotic while we waited for the results of a skin culture test which would determine what kinds of bacteria were present and what antibiotics would be effective.

At the same time Kyrie's infection was diagnosed, San Diego's Mary Ann Rose was trying to figure out why her Scottish Deerhound, Angelina, was not recovering from surgery for injuries received when she was hit by a car two weeks earlier. Rose and her husband are both physicians and Angelina had the best possible care at every stage. And yet, while she did fairly well when taking a 10-day course of prescribed post-surgery antibiotics, she went rapidly downhill in the 48 hours after the antibiotic treatment was done.

"She became very ill," Rose said. "She was weak, wouldn't eat, and had a fever for the first time since the accident." Over the next few hours, Angelina developed multiple ulcerated skin lesions all over her body.

Rose didn't waste any time. "I took her back in to the surgery clinic where she was operated on. It was a Saturday. They took one look at her and called board certified veterinary dermatologist Laura Stokking and said, 'We don't know what this is, but this is a really sick dog.' Dr. Stokking worked on her all day. She had IVs, and every inch of her body was cultured."

While caring for Angelina that day, Stokking saw evidence of some type of staphylococcus under the microscope. Knowing the dog had already been on two antibiotics that normally kill that bug, she started her on a different oral antibiotic as well as an anti-bacterial skin wash while awaiting test results. Angelina improved on the new treatment, and when the culture results came back, they confirmed that she had MRSI.

My dog Kyrie's culture showed she had MRSI as well. In fact, it indicated that two organisms were present. One was just what we expected, a methicillin-resistant staph, sensitive to a number of drugs including the one she was taking. But the other was a multi-drug resistant staph that was sensitive to almost none of the common veterinary antibiotics.

Still, Kyrie had gotten better while on the drug, so we continued the treatment and hoped for the best. Unfortunately, after the three-week course was finished, her symptoms returned with a vengeance. Back to the vet, where we faced some bad news about our options: amikacin, a drug that needs to be given intravenously every day, costs in the four figures, and has some very dangerous side effects; or chloramphenicol, a drug that wasn't included in the skin culture test that might or might not be effective.

I decided to go with the second option, primarily to avoid the stress of daily vet visits for Kyrie, and because the side effect risk, although far from negligible, was less for chloramphenicol. And at first, I assumed we'd gotten lucky, because the wound started healing immediately.

Unfortunately, it came back two days after a three-week course of chloramphenicol was finished, just like before. But I'd spent those three weeks researching MRSI and MRSA skin infections, and this time I tried dressings of medical-grade honey, which is often effective when used in combination with oral antibiotics. Within a few hours, the wound had started healing, and within two days it was finally gone. Today, three months after it all began, the infection seems to be eradicated, her coat has re-grown in the affected area, and we're hoping her next skin culture will show her to be free of the superbugs.

Meanwhile, down in San Diego, Angelina was fighting for her life. "She had an episode of septicemia (blood infection), and the sores were all over her body, and the hair just sloughed off, and they were oozing," said Rose. "I have never seen a dog that sick that survived."

The Roses and their veterinarians persisted with Angelina's treatment, and gradually she recovered. After just under a month, they tried to stop the antibiotic, but her symptoms returned almost immediately.

In the end, Angelina was on the drug for more than 12 weeks before her cultures came back negative for MRSI. "She's lost most of her hair," said Rose. "My husband, who is an infectious disease doctor, says that in humans, when you get these resistant staphylococcus infections, they will slough skin for several months." In addition to the lingering skin and coat problems, Angelina suffered damage that will probably be permanent to the joints in one of her legs that had become infected.

I spoke with Angelina's veterinary dermatologist, Laura Stokking, and she said that, while Angelina's case was a bad one, she's seen worse. "You know, it was easy with Angelina's parents because they're physicians, so they know a lot more," she said. "She responded pretty well. I have some cases where there is a substantially higher amount of the body that's affected and a lot more tissue necrosis, and the dogs are really systemically ill." She attributed Angelina's recovery, slow though it's been, to aggressive treatment.

I asked Stokking if it's just a coincidence that I heard of two cases at the same time, or if MRSI in pets is really on the rise. She said that MRSI infections were the hottest topic at the recent North American Veterinary Dermatology Forum, and while there is some increased awareness leading to more frequent diagnosis, there's no question the infections themselves are becoming more widespread.

"Definitely in dogs it's an emerging problem," she told me. "Up until recently, the bacteria that most commonly affected dogs didn't tend to trade resistance information with other bacteria the same way that the staph in humans did." Those days are gone, however, and she says both the incidence and prevalence of drug resistant bacteria are spreading in companion animals.

Given that MRSI infections are of increasing risk to dogs and cats, the most useful information a pet owner could get would be how to prevent them. To do that however, we'd need to know where the pets were getting the infections.

While humans frequently get the more severe strains of MRSA in hospitals, Kyrie was perfectly healthy and hadn't even been to the vet's office recently. And even though Angelina had recently undergone surgery and spent time in a veterinary hospital, she actually had the infection, although it was undiagnosed, prior to her accident and surgery, in the form of two lumps on her legs — lumps that were initially mistaken for spider bites.

Stokking agreed that the origin of most MRSI infections in pets is unclear, and wasn't surprised that Angelina most likely had acquired the bacteria before her surgery. "We don't usually see a link between hospitalization or veterinary visits and the acquisition of this strain of staphylococcus," she said.

What about the canine or feline equivalents of the daycare center or gym, such as dog parks, boarding kennels or groomers? "Contaminated water, contaminated shampoo bottles," she agreed. "It's possible."

Pets living in the same household with an infected dog or cat will sometimes get MRSI from the sick pet. (Humans virtually never get MRSI from animals, although we can transmit MRSA to them.) But neither Rose's nor my other dogs became infected, and that's not uncommon. Why did seemingly healthy dogs like Kyrie and Angelina become ill, when other also seemingly healthy pets in the same household didn't?

The truth is, we really don't know where dogs and cats are being exposed to these bugs, which makes it almost impossible to prevent our pets from getting them.

However, uncertainty about prevention doesn't mean there's nothing pet owners can do to minimize their pets' risk of resistant infections. Because rapid diagnosis and effective treatment are key to preventing the more serious forms of the disease, pet owners and their veterinarians need to be on the lookout for it.

They first need to be aware that many skin infections with MRSI or MRSA are initially misdiagnosed as spider bites, as both Kyrie's and Angelina's were. Stokking said that the Centers for Disease Control and Prevention have a poster used in human medicine that says, "Looks like a spider bite but isn't? MRSA." Since it's such a common misdiagnosis, she believes it's probably a good idea to do a skin culture on any suspected spider bite and any skin infection that doesn't immediately respond to the usual antibiotics.

Even though it was not the case for Kyrie or Angelina, there is one other factor that should make owners and veterinarians particularly alert for signs of MRSI in pets. "We do frequently see a history (in infected pets) of repeated use of antibiotics," Stokking told me.

Owners also need to be aware that trying to save money by delaying or skipping diagnostic tests can cost them much more money in the long run. A skin culture might cost over $100, but wasting time on an ineffective antibiotic can cost much more. The first drug Kyrie went on was priced at only around $40, but the second one was nearly 10 times that for a three-week supply.

And if you think my dog's prescription was expensive, want to know how much that course of amikacin — or, for that matter, vancomycin, the drug of last resort for resistant staph in humans — would cost? Around $1,000. Not to mention both have to be given intravenously and are highly toxic to the kidneys. Worse, over-reliance on vancomycin in human as well as veterinary medicine is leading to the further development of vancomycin-resistant bacteria, which is leading directly to the loss of human lives.

But the really bad news has nothing to do with your bank account. It has to do with the development of resistant bugs itself. Bacteria have a dazzling ability to trade genes and develop resistance, so strains that are susceptible to one drug today could easily be resistant to it tomorrow. Using an ineffective antibiotic, chosen without doing a skin culture first, can accelerate the development of additional resistance in bacteria. And that, again, threatens not only our pets but human health.

Given that risk and expense, as well as how painful and dangerous these infections are, an ounce of detection in the form of a culture may well be worth a pound of a very expensive cure.

"Don't be afraid to culture," Stokking said. "It's better to do a culture and then find out that it would have responded to cephalexin than not culture and let it go three weeks before realizing that you're dealing with a methicillin-resistant strain."

Laura Stokking PhD., DVM, DACVD is a diplomate of the American College of Veterinary Dermatology, and has published several book chapters and reviews in veterinary dermatology and has lectured veterinarians at national and local conferences. She is active in educating general practitioners in San Diego County on recognizing and treating resistant staph infections in companion animals. Christie Keith's full interview with Dr. Laura Stokking can be found at Pet Connection.

Christie Keith is a contributing editor for Universal Press Syndicate's Pet Connection and past director of the Pet Care Forum on America Online. She lives in San Francisco.

San Francisco Chronicle Article

[SIZE="2"]Angelina, a Scottish Deerhound, and owner Mary Ann Rose last November, before Angelina was diagnosed with a serious drug-resistant staph infection that almost cost her life. Photo courtesy of Mary Ann Rose [/SIZE]


Angelina's right wrist, today, with a mostly-healed MRSI lesion. Even though her latest cultures came back negative for infection, she has lost hair in areas all over her body, and it's unclear to what extent, and when, it will re-grow. Photo courtesy of Mary Ann Rose


Angelina's leg after several weeks of treatment for MRSI. Photo courtesy of Mary Ann Rose


Another one of Angelina's MRSI lesions, also after several weeks of treatment. Photo courtesy of Mary Ann Rose


A closeup of Kyrie's MRSI lesion shortly after the second round of antibiotics had started healing it. This wound was originally diagnosed, mistakenly, as a spider bite. It more than qadrupled in size in less than 24 hours, even while Kyrie was on antibiotics. It was also extremely painful. Photo by Christie Keith


At age 9, Kyrie, a Borzoi owned by SFGate.com columnist Christie Keith, had never been ill before a drug-resistant staph infection struck. Photo by Christie Keith


Although she still needs a final culture to determine if the bacteria has been eradicated, Kyrie's lesion has healed and her hair is growing back. Photo by Christie Keith

Thanks for all the info Deb, those pics look sore. Glad Kyrie is back on the road to recovery x

Makes sense that alot of what affects us eventually makes it's way into the animal world and as responsible pet owners we have to be extra vigilant and prepared to go the long haul for some of these cases that come up. I wonder how many cases we will start to see dumped on rescue that owners not so prepared cannot cope with. Very interesting read...thanks for posting it Deb.