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MRSA with underlying allergies
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MRSA with underlying allergies

My dog has been having skin problems since October 2009. It started with several small dry looking patches on her inner front legs and later inner back legs. After taking her to my regular vet she was diagnosed with a staph infection and put on Clavamox,  did not show improvement in a week and she was switched to Baytril and a medicated shampoo to be used 1-2a week. After a month with no improvement (actually worsening) we were refered to a dermatologist.At this point she had obvious collarettes and papulals with alot of redness and irritation on her inner/upper rear legs. She has also had irritation on her neck and chest area. She has had small patchy and widespread hair loss on her outter legs and sides, she has had little hair on her underside from the beginning. She was scraped and a culture was taken. In the mean time she was put on Cephalexin and told to use the shapmoo 2x weekly with 10 min contact time. She improved alot in a week. We then got back the results that she had MRSA and the cephalexin shouldn't be working. She was then started on Clinamycin and increase shampoo (Vet Solutions Universal medicated) to every other day. After 2 weeks there wasn't much if any improvement. Small bumps under the skin on the outside of her thighs and front legs. She is now on chloramphenicol and has been for 2 weeks. After one week of chlora she showed some small improvement but gets set back because she will itch her neck and head to the point where it is very irritated and red and bumpy. She only does this when she is left home alone in her crate. To combat this the dermatologist perscribed 4mg of methylprednisolone 1 tab for 5 days and then every other day for 4 days. After a couple of days on that she looked great, besides the hair loss she looked 100%. She got her last methyl pill yesterday and as we were weaning her down, her skin started looking worse again. A biopsy has been suggested. Any ideas on underlying causes? What may a biopsy reveal?
Type of Animal
:  
Canine
Age of Animal
:  
11 months
Sex of Animal
:  
Female
Breed of Animal
:  
Boston Terrier
Last date your pet was examined by a vet?
:  
January 29, 2010
State/Province
:  
NY
Blood Test Results
:  
Normal for Spay in Aug 2009
Other pertinent test results
:  
3 skin scrapes neg for demodex, fungal culture neg for ringworm, Woods lamp neg for ringworm. Multiple skin scrapes pos. for staph. Culture showed postive for Methicillin Resistant Coagulase neg Staph spp.
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931674_tn?1283485296
The staph infection, methicillin or not, is always secondary to an underlying cause, and in a young itchy Boston it is either food allergy or atopy (pollen/dust allergies). It sounds like the infection is better but the itch/underlying allergic cause persists and perpetuates the skin inflammation. If the rash/infection persists then development of resistance to chloramphenicol is possible. A skin biopsy would be supportive of an allergic diagnosis, and if the skin lesions appear unusual then biopsy would rule out unusual diseases such as urticaria pigmentosa. Since her itch improved with Medrol, she probably has atopy (although the only way to definitively rule out food allergy is to feed a prescription hypoallergenic diet for 6-8 weeks with no other foods or treats). Have antihistamines or a hypoallergenic diet been tried? Since her symptoms are worse in the crate, changing to a non-plastic kennel may be helpful, but if her symptoms persist despite resolution of infection, hypoallergenic diet trial, and changing the kennel, then the next step would be allergy skin testing and desensitization injections for pollen/dust allergies, to identify and treat the cause of her itch and secondary infections, rather than keeping her on steroids for the rest of her life.
Good luck,
Kimberly Coyner, DVM DACVD
www.dermvetvegas.com
6 Comments
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Avatar_f_tn
Ran out of space. I wanted to add that she managed to itch her self (neck and behind ears) pretty badly 3 days in a row. I am still working with the dermatologist, but I am wondering if anyone has seen something like this before. He is stumped because she is not responding to the antibiotics that the culture showed sensitivity for. I am feeling pretty helpless at this point and I am running out of funds.
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Avatar_f_tn
Thank you for the reply. About the food; she was on taste of the wild fish formula when this started and was then switched to holistic select lamb and rice because I suspected a food allergy. The food is not hypoallergenic but the 2 foods have pretty much no ingredients in common. I treat her with kibble and stuff her kongs with natural peanut butter and kibble. She had not had peanut butter prior to this problem beginning. As for the crate; it is metal with a plastic bottom and a fleece blanket. I have thought about it being the blanket but she itches when it is freshly washed and when it hasn't been washed in a week. She also sleeps on fleece on the couch. I am thinking about leaving her out of the crate to see if it a confinement thing. She has not tried antihistamines but I will bring them up to the derm as they would be an easy thing to try.

Is it possible the infection cannot fully resolve itself without the allergies being under control? Or should the infection be irradicated with the proper antibiotic regardless of allergies? We will probably go ahead with the biopsy but I am fearful that it could introduce the infection into deeper layers of her skin.
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931674_tn?1283485296
My preferred hypoallergenic diet is prescription Royal Canin rabbit/potato, and the key is to feed only the hypoallergenic food for 6-8 weeks, with no other treats, table scraps, rawhides, milkbones, peanut butter, chewable supplements or other foods. I have seen dogs allergic to lamb, rice, and fish. It would be ideal to remove the plastic bottom from the crate, and washing her bedding with dye/fragrance free detergent to see if that make a difference with her symptoms. If the fleece is real wool, then I recommend to remove it and use a synthetic bedding material. There is no doubt the infection is secondary to an underlying cause and will continue to recur unless the underlying issue is addressed. I have also seen a dog with MRSP become re-infected by licking of her ears and face from a companion dog in the household who was an asymptomatic carrier, do you have other pets?
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Avatar_f_tn
We do not have other pets but me and my boyfriend could be carriers. The only thing is that it doesn't seem to be reoccuring because she has yet to totally heal aside from when she was on the steriod for a few days. I don't really count that as being better because the dermatologist says steriods can mask infections. Unless, that allowed her to heal for a few days and then it reoccured when the steriods weren't there to control her allergies. On a side note, I asked my doctor about being tested for MRSA and possibly decolonized when I found out my dog had it, he pretty much told me not to worry about it unless I actually had problems. I wonder if it would be helpful to put her on steroids again for a few days and take her to get a skin scrape to see if the staph is still present.

I will do what you recommended with her crate. The blankets are synthetic. If plastic could be a problem, could a nylabone bother her? She has a non-flavored one that she chews on daily although she has had one since she was 4 months old. As far as the food goes, it would be hard for me not to give peanut butter right now because that is how she takes her pills and the stuffed kongs help occupy her in the crate. She had not been on a lamb diet before this and there were no grains in the food she was on when this started. Is it possible for her to have an allergy to something she hasn't had before? If I do need to feed a hypoallergenic diet, I like the idea of Royal Canin rabbit/potato, it looks like a much better food then all the hills perscription stuff, thank you for recommending it. Also, thank you again for your replies.
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931674_tn?1283485296
Yes, it is certainly correct that steroids can reduce inflammation associated with infection and make it appear that the infection is better when in fact it is not. I have had nice results using either Mupirocin antibiotic ointment twice daily or TrizChlor antibacterial spray once daily on affected skin in combination with oral antibiotics, and you can talk to your dermatologist about topical antimicrobial therapy if it is not already being performed. Dogs usually do not have MRSA (human origin staph infection), but instead usually have MRSP (which is adapted to dogs and usually is not a problem for humans with normal immune systems); you can read more about MRSP at http://www.wormsandgermsblog.com/uploads/file/JSW-MA2%20MRSP%20-%20Owner.pdf
The lamb/rice dog food you are currently using also has eggs and chicken fat, and lamb may have some similarities to beef, so I do not use lamb as a hypoallergenic diet. The rabbit/potato dog food also comes in canned form to hide pills in, so that can take the place of peanut butter.
Hope that helps, good luck
Kimberly Coyner, DVM DACVD
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