Pyoderma (bacterial skin infection), Interdigital Pyoderma in Dogs


Interdigital pyoderma and pododermatitis

Question: Dear Dr. Richards:

I have an 11-year-old shelty named Ben, whom the family love very much. He has a lesion on his right forepaw that seems to fit the description of "interdigital pyoderma" that you mentioned in a web-posted article involving a dog named Angie. I would deeply appreciate your advice on alternatives to surgery. His history may be summarized as follows.

About 2.5 years ago, I noticed that Ben had what appeared to be a small puncture between the outer two toes of his right forepaw at the juncture of the two toes and more towards the top of his paw than the bottom. The wound appeared neat as if made by the tip of an icepick. Ben walks regularly in a canyon that has plenty of foxtails that might have produced such an outwardly appearing puncture. After several weeks, the wound appeared to heal. But, with any daily walking of more than about a mile or so, it would re-open enough to bleed. He also walks with his right paw pidgeon-toed inward and with a slight limp that is more pronounced when walking down hill.

After several months, I took him to three different vets over the next year, none of whom knew what to make of the lesion, but all agreed that a foreign body should have worked itself out by that time. A fourth vet said that Ben had a tumor between his toes that had to be removed, so I okayed the surgery in February of 2001. This vet #4 said that the tumor was about a centimeter in diameter, but I personally was never able to feel it. Vet #4 removed as much tissue as possible without risking damage to the paw and toes. About two months later, the lesion returned between the adjacent pair of toes, and has subsequently spread very slowly up the paw (as may be seen in the attached images of 4/1/01 and 10/21/01).

The biopsy of the surgically removed tissue concluded the following. No evidence of malignant change in the tissue, but rather inflammatory and not neoplastic. Such a tissue reaction can be due to foreign body penetration or deep-seated chronic bacterial infection. Fragments of keratin appeared to be acting as foreign bodies, suggesting that rupture of a follicle may have released material which incited a focus of foreign body reaction. Neutrophila were seen mingled with macrophage-type cells, with neovascularity and granulation tissue formation seen in surrounding tissue. In short, the diagnosis was "focal pyogranulomatous inflammation, with secondary granulation tissue and tract formation."

I next took Ben to a 5th vet this past July who diagnosed the lesion as "interdigital granuloma" and had me give Ben a 30-day prescription of Baytril, along with regular Epsom Salts soaking of the paw. The lesion got a little bit better, but never went away, and is now much worse as shown in the attached image of 10/21/01. Ben also has periodic dark skin bumps that itch a great deal and eventually fall off, only to be replaced by 3-4 more elsewhere on his body. He has also been getting occasional yeast infections in his left ear. But outside of these skin problems, his health is excellent according to all vets who have examined him. By the way, he gets two small daily feedings of Science Diet, a mix of half the "sensitive skin" formula and half the "lamb meal and rice" formula.

So what should I try next? You suggested NeoPredef (Rx) and some sort of systemic medication as a possible treatment for Angie. I want to avoid a second surgery for Ben, as it would have to take much of his right forepaw. Is there any way I can stop the growth and discomfort of Ben's lesion? I would be so very grateful if you could suggest some actions I might take. I cannot resist also showing you what a beautiful dog he is (third attached image).

Very sincerely, Charles

Answer: Charles-

There are several possible approaches to the sort of problem that you are having with Ben that might help. I do not practice in an area in which foxtails are found, so I have very little opportunity to see the wounds from these. We have seen around three dogs with foxtail problems after trips out West. These do seem to be capable of causing long term infections that don't stop until they are removed. However, since surgery has been done once this seems like less of a possibility. I'm just not sure that the continued presence of a foreign body can be ruled out and if there is one, surgery still might be the best option.

We do see a lot of dogs with pododermatitis and interdigital pyoderma who have persistent cystic sores between the toes that often open and drain, though. Over the years these have been extremely frustrating to treat successfully with any one approach. So the following is a list of things that have worked in at least a few dogs, with some notes about how we use them:

Mupirocin ointment (Bactoderm Rx). Actually, we just started using this ointment more frequently. We like it so far and it seems to be helping one of our chronic cases some -- but it is sort of early to be sure.

Metronidazole (Flagyl Rx) has worked wonders for two or three cases of interdigital cysts in our practice. We had one dog who had been to four or five vets prior to moving into our area and had been treated with everything else on our list. He responded within ten days to metronidazole and the cysts actually cleared up. They have returned a couple of times now but have continued to respond to metronidazole. Right now, this is our favorite treatment for resistant cases of this problem but we could just be on a lucky streak since other things have seemed to work well for a while in the past.

Doxycyline, like metronidazole, has worked well for a couple of dogs who did not respond to treatment with other antibiotics. These cases have been a little more sporadic for us but it still seems worth a try to us.

Fluoroquinolones (Baytril Rx, Dicural Rx, Orbax Rx, others) are the most commonly recommended antibiotics in the dermatology literature. These are broad spectrum antibiotics that generally penetrate tissue well. Even though your vet chose the antibiotic group to treat with that is usually considered best, sometimes fluoroquinolones just don't work.

Clindamycin (Antirobe Rx) is an antibiotic that has good activity against anerobic bacteria which seem to be involved in some cases of interdigital cysts. It is often used in combination with fluoroquinolones but can also be effective alone in some dogs.

Cephalexin ( Keflex Rx) is our general favorite antibiotic for skin disease, especially in older dogs. We are comfortable using it long term, which is often necessary to control skin infections. It seems to be among the safer of antibiotics, although no antibiotic is totally risk free. If there seems to be any response to cephalexin early in treatment we usually try it for at least three weeks. I like trimethoprim/sulfa combinations (Tribrissen Rx, Bactrim Rx, others) but am reluctant to use these in older dogs because the side effect we see most often is reduction in tear production and older dogs often have problems with tear production as it is.

A bacterial culture and antibiotic sensitivity testing might be helpful in choosing an antibiotic but our experience with this has not been overly encouraging. We get a lot of staph bacterial growth, usually sensitive to most antibiotics we use even in infections that haven't responded to a couple of the antibiotics -- so we figure that we aren't really growing the organism causing the problem most of the time.

So our basic approach is to start with cephalexin and then move on to the other medications on the list, except that we often use cephalexin and metronidazole together rather than withdrawing the cephalexin. We have been using the topical mupirocin as an additional therapy in the last few cases but don't have much feedback on it, yet. We use fluoroquinolones last, mostly based on expense but also because we like to have an antibiotic that we don't use much, too. That is just a practice quirk, though. It would be easy to argue that using them first might save money if they work best.

I hope that this helps you help Ben.

Mike Richards, DVM 11/11/2001

Vulvar fold pyoderma/cellulitis

Question: Katie is being seen by a dermatologist for an ongoing skin problem, Vulvar fold pyoderma/cellulitis. She has been on a high dosage of antibiotics for several months. We have seen some improvement in her skin condition.

Answer: Vulvar fold pyoderma can sometimes be controlled through surgery to reduce the folds. This should be done by a surgeon who is familiar with the procedure, though.

Mike Richards, DVM 9/22/2001

Lip fold pyoderma in Golden

Question: Dr. Richards:

I have a 10 year old golden retriever. From time to time over the past 5 years or so, she's developed a bad, rotten fish type of smell on the outside of her mouth, under one of her bottom lips, in the fur area. Her fur in that area becomes a little sticky and a little red and seems to bother her a little. I usually clean it up with the chlorhexaderm oral solution and put some anti-biotic ointment on it and it usually clears up within a few days.

Any ideas what this could be from? Her teeth are in good shape and she gets them brushed every other day or so, so I don't think it's from dental disease.

Thanks. Vanessa

Answer: Vanessa-

It sounds like you are describing a problem that is referred to as "lip fold pyoderma". This is infection in folds of the lip that usually occurs on the lower lips, often right at the point that the upper canine tooth touches the skin of the lower lip when the mouth is closed.

There is no problem with using chlorhexidine gel or benzoyl peroxide shampoo to control these infections, if topical treatment will work. Sometimes oral antibiotics are necessary to get control of these infections. If you find that this problem gets worse over time, or if you get tired of treating it intermittently, reconstructive surgery of the lower lip (cheiloplasty) will usually resolve the problem and may even be less expensive than repeatedly using medications, over time. This is not a technically difficult surgery and most general veterinary practices can do this. This problem is rarely related to the teeth, other than occurring where the upper canines touch the lips in many cases.

Hope this helps some.

Mike Richards, DVM 1/3/2001

Skin infections (pyoderma)

Question: Dear Dr. Richards:

My dog, Sammy, is a 75-lb mixed breed. He looks like a Shep/Rotty mix. Three months ago he would yelp when I would touch a spot on his back; near and around his withers. When I took him to the vet, we couldn't do anything to reproduce this symptom. Accordingly, the vet prescribed Prednisone because he thought Sammy had a pinched nerve. My dog did not do well on Prednisone and I weaned him off it in about a week. About six days later I brought him back to the vet because his skin was flaking (dandruff) and he was diagnosed with a staph infection and given Ceflexin (sp?) which worked well. We didn't make any connection back then.

Now, three months later, the same sequence of events has occurred. First the yelping -- the vet thought it might be bone-related -- and then the itch and scaling. We finally realized the pain he had three months ago was probably associated with the staph infection, just like it is now.

What can be causing this infection, how can I treat it, and more importantly, is there any way to avoid it occurring in the future? Is it contagious to humans or other animals? He enjoys the local dog-park and I'd hate to have to avoid going there with him in the future.

Thanks, Brad

Answer: Brad-

Skin infections (pyoderma) occur as primary infections (no underlying cause) and as secondary infections to other diseases, especially allergies, parasites and immune system disorders. It can be very hard to figure out whether a skin infection is primary or secondary in some dogs. The presence of pain or tenderness in the areas that becomes infected, prior to visible signs of infection, makes the probability of this being a secondary infection a little higher, probably. On the other hand, when the clinical signs clear up with antibiotic therapy alone, it makes a primary bacterial skin infection more likely --- so essentially you have a toss-up going on and you and your vet will have to work through this over time to determine what is going on.

The biggest mistake that people make when treating skin infections is not treating them long enough. If an infection responds to antibiotics and then recurs, it is a really good idea to use antibiotics for at least 6 weeks and possibly 8 or more weeks, to try to eliminate the infection. If that doesn't work, it may be necessary to treat intermittently, or even to treat continuously, to control some skin infections. Cephalexin is usually a good choice since most of the time these are staph skin infections.

It is a good idea to make sure there are no fleas, no mites (Demodex or Sarcoptes) and to pay attention to when the skin infections occur to try to see if there is a link to something, or if they occur the same time each year. This gives a hint about underlying causes.

I know of no evidence that staph skin infections from dogs are contagious to humans and there are only scattered reports in which vets worried over potential contagiousness between dogs. Most of the time these are normal bacterial residents of the dog's skin that just get out of hand because a particular dog has some problem controlling them.

Good luck with this.

Mike Richards, DVM 11/19/2000

Recurrent skin infection possible

Question: Dear Dr. Richard: I have just become a subscriber to your service and look forward to having you answer future questions.

My 2 year old black lab has been diagnosed with a bacterial skin infection. He does not have any rash and is not scratching. He has been on antibiotics for 2 weeks and still is loosing a lot of hair. My vet does not seem concerned about the hair loss. This is his third time with a skin infection. They ruled out autoimmune problems the 2nd time he had this problem. Each time the symptoms are a little different. What do you think?


Answer: Lisa-

Labrador retrievers shed a lot, at least based on the ones in our practice. If there is a lot of shedding but there are no visible thin patches in the hair coat it is possible that this is just normal shedding behavior.

On the other hand, if there is thinning of the hair coat, scales in the hair coat, small patches of hair loss with scaling along the edges, red bumps in the skin, small scabs or visible pustules (pimples) on the skin then a bacterial skin infection is likely. Labradors are also somewhat prone to having bacterial skin infections and if the signs above are present and there is not much itchiness that would be pretty typical of bacterial skin infection (pyoderma). It can take a fairly long course of antibiotics to control pyoderma in dogs, sometimes several months or more.

There can be underlying causes for recurrent skin infections, such as skin parasites (especially fleas), allergies, immunodeficiency disorders (these are actually hard to completely rule out), hypothyroidism and hyperadrenocorticism. The hormonal disorders are pretty uncommon in young dogs, though.

I hope that this helps some. I would be glad to try to help more if you can send more information on the clinical signs that you have seen, when they started and what has been done to treat these problems.

Mike Richards, DVM 10/17/2000

Skin Condition in French Bulldog

Question: Cowboy, my Frenchie, has developed some small patches on his forehead that look and feel like small bumps. They don't seem to bother him. The hair is sparse or absent on these spots; not particularly inflamed.

We live in a dry, mountainous area. Therefore, I have attributed the condition to allergies, dryness, or perhaps the need for more oil in his diet. (He seems to crave the skin lotion I apply after a shower.) His coat is shiny and appears healthy, maybe with some signs of skin dryness and flakiness.

We have an appointment with a new vet tomorrow to investigate this skin situation, so, I would like a bit of input from you about this. You have been very helpful in the past; it seems like most times you and I are "on the same page" diagnostically. (I'm sure not a vet but a long-time dog owner, breeder, and rescue program participant. Just have some experience with animal health.)

Look forward to hearing from you.

And again, many, many do a great service!!


Answer: Jean-

Skin bumps on short haired breeds tend to be a sign of pyoderma (skin infection). It is really hard to figure out what to do when these are confined to a small area of the skin. It often seems like overkill to use oral antibiotics for several weeks but topical treatment with antibacterial shampoos is not too reliable. We have seen a couple of cases of demodectic mange that presented as scattered bumps associated with hair follicles. All of these were in young dogs, as far as I can remember. Ringworm sometimes looks like this. A few dogs are probably having reactions to insect bites or contact irritants. Finally, there are a number of skin tumors that occur and sometimes they do start out looking like minor infections or benign bumps. The odds favor a skin infection by a pretty wide margin, though.

It is pretty important to check the skin out very carefully for bumps in other places and to look for enlarged lymph nodes. Once in a while we find a patient with a subtle generalized pyoderma that only become really evident when it causes a few bumps somewhere.

Of course, you are already taking the best step by getting your vet to examine Cowboy tomorrow!

Mike Richards, DVM 6/23/2000

Bacterial Skin Infection

Q: My friend has an 8 year old female Samoyed with a skin problem The vet is treating it with antiobiotics and the dog has been on them for 4 weeks. Started at tail with skin becoming scaly in spots. After shaving affected area skin appears to have brown rings on it. Areas clear up and hair grows back but then new areas appear on other parts of the body. We thought with the antibiotics the condition would not spread. But it is. Do you have any idea for alternate treatment? Diane

A: Diane- I would still be suspicious of a bacterial skin infection with the signs you describe, so continuing the antibiotics seems like a good idea to me. It might be worth attempting to get a culture from a skin lesion to identify the bacteria involved and get an idea of what antibiotics kill it, if this is possible. Sometimes this doesn't work and often it is expedient just to change antibiotics, making sure to stick to ones that have a good track record of helping with skin disease. Sometimes the bacterial infection has an underlying cause, such as allergies, immune mediated disease, systemic illness or skin parasites. Checking for these conditions may be necessary if the problem continues. There are veterinary dermatologists and it can be worth the drive to one for difficult skin problems. They see the resistant and atypical cases of skin disease and often can pick up patterns of disease not apparent to a general practitioner or do specialized testing not available at many veterinary offices.

Good luck with this. Mike Richards, DVM

Interdigital Pyoderma

Q: I have a westie who develops recurrent cysts between his front paws. Our local vet pokes him full of steroids and antibiotics but they only recur so that he is seldom free from them. They are quite sore and do affect him. He is 11 years old and quite game for daily long walks, is not overweight but is stocky. Our local vet is happy with him and feels that he ought to live with the problem and just seek aid when it flares up badly. 25 years ago we had the same problem with a Jack Russell who became reluctant to exercise and became somewhat overweight ultimately causing his death. I hope that in 25 years some progress may have occurred. I do appreciate your availability on the net. I do the same as a dentist and feel; that I am being useful as I am sure do you. I hope you can help.

A: Westies are extraordinarily difficult patients when it comes to skin disease. I can understand why your vet is content with intermittent success in repressing the clinical signs. Sometimes it is hard to achieve that level of success in dealing with problems like interdigital pyoderma in Westies. On the other hand, he is likely to live a long time and I can understand your desire for a long term solution to the problem. My best advice would be to seek the help of a veterinary dermatologist if one is available in your area. Most of the time, the problem with Westies is allergic in nature. They are very prone to atopy and more prone than most breeds to food allergies. Allergy testing and hyposensitization will help many dogs with atopy. Food trials and hypoallergenic diets help with the food allergies. Intradermal skin testing still seems to be the best method of determining what a dog is allergic to for inhalant allergies (atopy) and dermatologists are the most experienced at this sort of testing in most areas. If you do not have a veterinary dermatologist available or do not think that you would be willing to do hyposensitization (usually you have to give the allergen injections yourself due to the schedule), then you may have to accept the current status. Your vet probably is doing pretty well even though it is frustrating. It does seem like we should have a better solution after all these years. I wish it were so!

Mike Richards, DVM

Last edited 11/17/04


Michael Richards, D.V.M. co-owns a small animal general veterinary practice in rural tidewater Virginia. Dr. Richards graduated from Iowa State University's College of Veterinary Medicine in 1979, and has been in private practice ever since. Dr. Richards has been the director of the PetCare Forum...