Skin Infections Part 2

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Skin infections with bacteria and yeast can make dogs and cats very itchy. Veterinarians often treat with topical therapy, like medicated bathing or spray. Sometimes the infection is too deep or severe for topicals. In this episode, veterinary dermatologist Dr. Alicia Webb Milum discusses how skin infections are diagnosed and when sets decide to reach for oral or injectable medications to treat those infections. If you have an itchy dog or cat, this episode is packed with information to improve your pet’s health.

Welcome Back, Dr. Alicia Webb Milum

[00:01:06] Dr. Lancellotti: Welcome, everyone, to today’s episode of Your Vet Wants You To Know. I’m joined, again, by Dr. Alicia Webb-Milum, who joined us on the last episode, where we started talking about skin infections, how to diagnose them, and a little bit about how to treat them. Today, we’re going to be talking about our different antibiotic options, such as oral or injectable antibiotics, which are used to treat infections on the animals’ skin. Welcome back, Dr. Webb-Milum. 

[00:01:36] Dr. Webb-Milum: Thank you so much. I’m glad to be here again. 

Dr. Alicia Webb Milum and her three boys
Dr. Alicia Webb Milum and her three boys.

Topical vs Systemic Treatment for Skin Infections

[00:01:38] Dr. Lancellotti: So in the last episode, we were talking a little bit about Carolina. She was a bulldog that had a pretty significant infection and some steroid side effects. You told us about how we were limited in our antibiotic options for her, so the owners did a really good job of clearing her infection with topical therapies. That was a great story. The listeners can check out a picture of Carolina’s skin on the website, so that they can see how she was doing after appropriate management of the infection, as well as getting her off of steroids. But I want to talk a little bit more about systemic antibiotics, today. Topical therapy is really helpful and helps us to reduce the risk of developing resistant infections (where our antibiotics may not work), but sometimes it doesn’t completely clear the problem. Can you just briefly describe for me the difference between topical versus systemic antibiotics?

[00:02:38] Dr. Webb-Milum: Sure. Last time, we talked a lot about topical therapy. It’s important that we’re choosing the correct product and that we are doing the bath in a way that’s going to be most effective. Topical therapy is trying to treat the infection from the outside versus from the inside. This is extremely beneficial in that it reduces our reliance on drugs. However, there are some cases of skin infections that are deeper, or some patients and pet owners that are not the best candidates for topical therapy alone. In those cases, we do need to consider our options for systemic therapy, a treatment that works from the inside of the body (via a pill, or in some cases, an injection). It’s called ‘systemic’ because once the medication is absorbed, it has to make its way throughout the body’s systems (via the blood vessels) to get to the target tissue. In our case, it’s the skin.

3 Considerations for using Antibiotics for Skin Infections

Dr. Webb-Milum: There really are three important points to consider. One, the skin is a very large organ, but there are actually not a ton of blood vessels there. This means that it’s actually hard to get enough antibiotic from the stomach to the skin, and we often need to use higher doses for the antibiotic to be effective. But when we’re using higher doses, we can see more side effects (such as vomiting and diarrhea). 

[00:03:54] Dr. Lancellotti: Yeah, I think that’s a key point to address as far as using antibiotics versus using our topical therapy. There are more side effects when we’re using an oral medication compared to when we’re putting something on the surface of the skin. We talk quite a bit on the show about risk versus benefit. There can be a huge benefit from our topical therapy with minimal risk associated with it. Depending on the antibiotic, your risk-benefit analysis is going to be different. Some antibiotics have higher risks associated with them, but there’s certainly going to be a benefit to the antibiotic if we know it’s an effective antibiotic for the type of infection that the animal has. 

[00:04:37] Dr. Webb-Milum: Certainly. The second important point is that while we are targeting a specific bacteria causing an infection on the skin, as we mentioned on the last episode, we are covered in various types of bacteria and yeast. So we have lots of other bacteria that populate our skin and our intestinal tract. When we use an antibiotic in our entire body systems, that antibiotic not only affects the bacteria on the skin, but also those other bacteria on our skin and in our gastrointestinal tract. This is one of the reasons that we do see the diarrhea with antibiotics, because we are inducing an imbalance of the bacteria in the gut- this is the “bystander effect.” 

[00:05:18] Dr. Lancellotti: Yeah. Oftentimes, I will hear pet owners ask me if they should be giving their pet a probiotic when they’re taking an antibiotic. I’ve got a great episode coming up, with one of our resident mates, Dr. Christie Yamazaki, all about probiotics and their use in veterinary medicine. But you’re absolutely right. The antibiotics aren’t just treating what’s on the skin. They’re going to affect every bacteria that they come in contact with in the body. We can see disruption of the normal gut microbiome because we’re using oral antibiotics when we treat the skin.

[00:05:52] Dr. Webb-Milum: Absolutely. The other major point with using a systemic antibiotic is that antibiotic usage is a known risk factor for the development of antibiotic resistance. There are many reasons for this. An overly simplified explanation is that when we use an antibiotic attempting to kill a population of bacteria, there’s likely going to be some bacteria that survive, because they have a genetic mutation that gives them a survival advantage against that antibiotic. We’re not all the same, and neither are bacteria, so if there is a survivor, that survivor can then go on to repopulate the skin with copies of itself. And when that happens, the infection is now resistant and we have to alter our approach to treatment. We really are in sort of an arms race with bacteria. It’s really important to think of our goals in treating infection both in the short term, but also in the longterm. Remember, we are primarily seeing secondary infections due to chronic diseases, and this is not likely to be the last infection that the pet has. So we really need to think about the long-term implications of any treatment that we pursue, as well.

[00:06:55] Dr. Lancellotti: Yeah, absolutely. Especially because one of the most common primary diseases (as we’ve discussed) is allergies, which really starts to develop in young animals. Think about this animal that is going to have a lifelong disease, already developing infections at 1-3 years of age. If we use antibiotics time after time and don’t address the underlying disease properly, that animal will then be set up for developing antibiotic resistance at some point in its life. And the stronger the antibiotics, the more risks we have associated with them. So if there’s any way to clear that infection with topical therapy, allowing me to avoid using an oral antibiotic, I will strongly encourage pet owners to “bathe, bathe, bathe.” 

[00:07:45] Dr. Webb-Milum: Absolutely.

severe infection on belly and legs of a dog from long term steroid use
Severe infection on the belly and legs of a dog secondary to long term use of steroids for asthma.
Severely infected and swollen paw from environmental allergies.
Severely infected and swollen paw from environmental allergies.

Some infections must be treated with systemic (oral or injectable) antibiotics to completely clear the infection.

How Do Veterinary Dermatologists Treat Skin Infections?

[00:07:47] Dr. Lancellotti: I asked you this question on the last episode, but when you approach skin infections, what is your approach?

[00:07:54] Dr. Webb-Milum: Unfortunately, we are seeing a number of infections with significant resistance patterns. I am usually seeing dogs that have been on antibiotics, repeatedly, in the past. I rarely start with systemic antibiotics first, unless I am very worried about that infection being life-threatening- which is very rare. If an infection is superficial and pretty mild, I often guide a pet owner about first pursuing topical therapy, alone. And if I deemed the infection to be moderate to severe, I will submit a test called a ‘culture and sensitivity.’ This test is performed by swabbing the infected area and sending that sample to a lab to grow the bacteria. Then, we do special tests to identify what it is and how we can best kill it with antibiotics. It’s really important to understand, though, that a culture needs to be performed along with cytology, so that we can interpret the culture, because the skin is just not a sterile surface.

[00:08:46] Dr. Lancellotti: Yeah. I tell owners that all the time. I think that’s a really important point. If you’re interested in hearing more about cytology, I’ve got a great episode coming up all about cytology with Dr. Ashley Bourgeois. When we’re doing a cytology combined with a culture, it gives us an idea of what bacteria we really need to be focused on, as far as treatment. Oftentimes, the culture may grow multiple strains of different species of bacteria, and each one of those strains of bacteria has a different susceptibility to different antibiotics. When I am picking an antibiotic, I want to pick an antibiotic that is going to be most effective against the bacteria that is causing the most significant problems on the skin. And the only way that I’m going to know is if I take that glass slide, press it against the area where there’s infection, and I look under the microscope and see what type of bacteria those white blood cells are eating. Those are the ones that I really want to make sure that I’m using antibiotics against.

[00:09:55] Dr. Webb-Milum: Absolutely. That’s important because if we are not focusing just on the primary bacteria that’s causing a problem, we really run the risk of using an unnecessarily broad antibiotic. So that’s a great point. 

image of bacterial skin infection as seen under the microscope

What is a Culture for Skin Infections?

[00:10:07] Dr. Lancellotti: Tell me a little bit about the culture. How long does that usually take for us to have some more information? 

[00:10:13] Dr. Webb-Milum: The culture can really take around 7-10 days to return. In the meantime, I talk to the owner about getting really diligent about topical therapy while we’re waiting. This usually consists of a special medicated shampoo, chosen based on what I’m seeing under the microscope. It also frequently includes antiseptic foams, sprays, or wipes, depending on the pet and the body area effected. The beauty of the diversity of these products is that we can really choose a product that has the most chance of success- which the pet owner will be able to give on a regular basis. 

[00:10:47] Dr. Lancellotti: Yeah, I love that. I think that’s such an important point. We mentioned talking to your veterinarian if you’re having problems doing medicated bathing because some of these other topical therapies provide us with solutions to those problems. Sprays, wipes, or foams can be used on smaller, localized areas of the body, rather than having to go through a full bath routine. This makes it a little bit less of a hassle for the owner to actually treat. I also think it’s important when you’re picking a different type of topical, other than a shampoo, that the pet owner communicate to the veterinarian about their animal’s particular temperament. And I’ve talked on this show quite a bit about my own allergic dog with Cushing’s Disease, Russell Sprout. Russell sprout has recurrent infections because he has both allergies and Cushing’s Disease, where his immune system isn’t working as well as it should be. Certain types of topical therapy would not be good for him. He has some behavioral issues as well. We’ve worked very hard to get him to a point where he no longer tries to bite me when I’m trying to treat him. Any type of spray that I would use topically would come with him trying to bite me, because he gets significantly anxious with a spray. But I can use foam or wipes without any sort of problem. So I think that’s a really important thing to have a discussion with your veterinarian about (if you know that your animal will be averse to different types of topical therapy), so that they can help you brainstorm and find one that’s actually going to work without causing anxiety between the pet or the pet owner.

[00:12:34] Dr. Webb-Milum: Absolutely. Because our goal is a happy pet, a happy pet owner, and protecting that relationship. It’s really a balance between treating the disease process and not harming that human-animal bond. 

[00:12:46] Dr. Lancellotti: Yeah. That’s really what we’re all about. We’re trying to make these animals feel better, so that they can have a better relationship with their family.

Petri dish with bacteria
During a culture, the bacteria is grown on a Petri dish, then tested to see which antibiotics may be effective.

Using a Culture for Treatment of Skin Infections

Dr. Lancellotti: Tell me a little bit about what you do once you get the culture results back. 

[00:13:00] Dr. Webb-Milum: After I get the culture results back and evaluate them, before I make a recommendation to start an antibiotic or not, we check on the pet and see how they’re doing. I really don’t expect that the pet is going to be completely better in 7-10 days, but if that pet is at least 60% better, or continuing to show ongoing and significant improvement, I really counsel the owners to hold off on antibiotics- even if we do have a sensitive strain of bacteria with fairly safe options. And I’m really having good success with that. 

[00:13:29] Dr. Lancellotti: Yeah, I love this approach so much. I have definitely been doing this with my pet owners, as well. We’re going to start topical therapy right away, because we know it should be effective for most of the bacteria and yeast that we see. If they’re getting much better and we’re headed in the right direction, that gives me the opportunity to hold off on using those antibiotics that carry the risks of gastrointestinal upset, disrupting the gastrointestinal microbiome, or developing resistance with the use of antibiotics. If it’s possible to keep going with the topicals, I love having owners continue to do that. 

[00:14:11] Dr. Webb-Milum: It is one of my favorite things. It is really satisfying.

Skin Infections with Yeast

[00:14:16] Dr. Lancellotti: So tell me a little bit about yeast infections. This is a little different than bacterial infections.

[00:14:22] Dr. Webb-Milum: For yeast infections, it depends on the severity of the symptoms and whether that dog is otherwise healthy. Just like bacteria, it’s still important to determine why that dog has yeast infections and manage that underlying disease. In regard to allergies, there are actually some allergic dogs that very well might have a hypersensitivity or an allergy to the yeast, Malassezia, itself. So treating that can be really critical to managing that patient’s symptoms. 

[00:14:47] Dr. Lancellotti: Yeah. I’ll often mention to owners that the animal is infected with yeast, but oftentimes, we see them be allergic to yeast too. It’s not just that they’re itchy because they’re infected, they’re extra itchy because they’re having an allergic reaction to the overproduction of their body’s natural yeast population. So it’s important to not only treat the yeast, but also to work on addressing the underlying allergy. I talked in episode 8 on immunotherapy and malassezia (yeast) are actually one of those things that we can work on desensitizing allergic animals to. So if you have an allergic animal and you’re considering doing allergy testing, this may be a great way to help get the itching under control if they have a yeast allergy.

Treatment for Skin Infections with Yeast

Dr. Lancellotti: How about if they’ve got severe infections with yeast that may not respond entirely to topical therapy? 

[00:15:41] Dr. Webb-Milum: If I have a severe infection in an animal that’s pretty miserably itchy, I will reach for an antifungal medication called ketoconazole. This medication can be a little tricky because it can affect the liver. Personally, I’m checking liver values really closely. I tend to get a baseline liver value, and then if I’m continuing it for longer than 4 weeks or so, I tend to keep an eye on those going forward, as well. Ketoconazole also interacts with a long list of other medications. It’s really important that if your veterinarian is talking about using the medication ketoconazole that you make sure that they are very aware of all other things (even supplements) that you are giving your pet.

[00:16:21] Dr. Lancellotti: Yeah, absolutely. Ketoconazole will affect the liver, which is the organ in the body that processes a lot of medications that we use. If we’re using ketoconazole, it may make those concentrations of other medications in the body higher than they would be if the animal wasn’t taking ketoconazole. Again, just having really good communication with your vet about what the animal is receiving and what’s going on with your pet is going to be crucial in having a positive, successful outcome. 

[00:16:54] Dr. Webb-Milum: I think that I say this phrase more than any other- topical therapy is critical and extremely helpful. These yeast live on the surface of the skin and we have access to that. 

[00:17:07] Dr. Lancellotti: Yeah, absolutely. And because the yeast live in those few surface layers of the skin, we can actually see that exfoliating (especially thick, chronically infected skin) can be really helpful in being able to clear a yeast infection. Sometimes, especially in those really thick neck folds that some of the larger allergic dogs have (labs, German Shepherds, or golden retrievers), where the skin on their necks just kind of comes together and traps all that moisture, I will have owners take a washcloth with the medicated shampoo on it and physically scrub that skin. They’re exfoliating those surface layers where the yeast live, but then they’re able to apply the medicated shampoo to the underlying skin to treat the yeast that’s still there. 

[00:17:58] Dr. Webb-Milum: Yeah. That’s a great point. We can’t treat through grime. Sometimes, in these really grimy areas, I will actually use Dawn dish soap to break that up. You have to be careful with that. Over time, that can be drying. But in the acute or early phases of treating them, sometimes, that can be helpful to remove that debris so that the medication can access the skin surface. 

[00:18:22] Dr. Lancellotti: Yeah, that’s a really good tool for breaking up a lot of the crust and grease that can be on the surface of the skin, so that our medicated shampoo can be more helpful. 

red belly and legs from yeast infection on the skin of a dog
Severe redness, hair loss, thickened skin, and itching from yeast infection on a dog with yeast allergies.
Dark staining of the hair and skin can occur with yeast infections on the skin and claws.
Normal, lighter hair has grown in following treatment of yeast infection with oral antifungal medication.

What to Know about Skin Infections

Dr. Lancellotti: We have a couple of great episodes coming up with another veterinary dermatologist, Dr. Megan Painter, who’s going to be talking about ear infections and getting into depth about those. If you’re interested in hearing more about ear infections make sure you hit the subscribe button, so that you don’t miss those episodes when they come out. We have talked a lot about skin infections, but I want to just give you the opportunity to reiterate some of the big takeaway points that you’d like pet owners to remember. 

[00:18:59] Dr. Webb-Milum: Sure. There are two big takeaway points from this talk. Infections are super common and they can cause a pet to be extremely itchy. If we neglect to manage the infections, we often have a hard time managing that pet’s itchy symptoms. Then, we enter the dangerous territory of immunosuppression when we reach for more (and more and more) symptomatic medications. Often, I hear pet owners describe that medications to treat allergies (Apoquel, Cytopoint, or Atopica) had initially controlled the pet’s symptoms in the past, but those effects seemed to be diminishing over time. This is almost always because that pet has developed an additional trigger, and secondary infections are usually the prime suspect. Once we treat the infection, that dog can almost always be managed again. This is what happened in Carolina’s case. Her previous allergy medications were really no longer working, so the solution was to reach for more potent medications, but this did not solve the problem- it created additional problems. 

[00:20:00] Dr. Lancellotti: Yeah, you’re so right. I hear pet owners tell me all the time, “Cytopoint really worked those first couple of times it was given, but it stopped working,” or, “It only worked for a couple of days the last time.” And sure enough, when I start looking around and trying to evaluate what’s going on with the skin or (especially) the claws, I find infection. That’s a big reason why our allergy medications no longer provide the pet with relief, because they don’t treat itch associated with infection. They treat itch associated with allergies, so addressing that infection is really crucial to providing your pet with relief. 

[00:20:41] Dr. Webb-Milum: Absolutely. The second major takeaway is that antibiotic resistance is real, and it’s appearing to become more common in both human and veterinary medicine. It’s really important that we are all responsible in our approach at dealing with a serious issue and realize that our choices do have impacts. Whenever possible, we should really try to avoid antibiotics and focus our efforts on topical therapy, because when that’s used correctly, it works. Again, we see this in Carolina’s case. She had no reasonable antibiotic options left to treat her skin infection, but her mom did not shy away from the task, and we were able to clear that infection without the use of more antibiotics.

[00:21:20] Dr. Lancellotti: I love when pet owners are putting in the effort and they can see the dramatic results, the way that the pet owner did in Carolina’s case. I think that is so hugely rewarding, not only for the pet, but also the pet owner- and the veterinarian who’s working with them. I don’t think pet owners understand just how satisfying it is for us to see an animal doing so much better, using a therapy that is safe, effective, and life-changing for them.

[00:21:53] Dr. Webb-Milum: I do think it’s important though that we communicate why, and commend those owners for putting in that time and effort. It’s a lot of work, but it does have significant payoff. 

[00:22:03] Dr. Lancellotti: I do keep a pack of ‘gold-star’ stickers in my drawer for those owners that are doing such a good job. 

[00:22:08] Dr. Webb-Milum: I love that! 

[00:22:11] Dr. Lancellotti: A lot of family veterinarians are very comfortable managing pets that have skin infections, but there is a link to the American College of Veterinary Dermatologists on the website under the resources section, if you would like to consult with a specialist. If your pet has had skin infections, I would encourage you to join the Facebook group, Your Vet Wants You To Know, so that you can talk to other pet owners.

Scratching the Itch

[00:22:49] Dr. Lancellotti: I always like to end each episode with a segment called Scratching The Itch. Scratching The Itch is designed to highlight a product or a website, or a human interest story- something that just provides relief or makes you feel good. Hence, scratching the itch. Dr. Webb, do you have a ‘scratching the itch’ for us, today? 

[00:23:09] Dr. Webb-Milum: Yes. As you know, I am fascinated by Monarch butterflies. They are really a “canary in the coal mine” of the overall health of our environment and they have a fascinating life cycle. Monarch butterflies are reliant on one type of food for their young. They only lay their eggs on milkweed, and baby Monarch caterpillars only eat milkweed. There really is a grassroots effort of people creating Monarch waystations to help facilitate the continued existence of the Monarch butterfly. I do this with my children. It is so fascinating and satisfying to see these butterflies continue their life cycle on my property. If you are interested in this too, you can find out how to make your own Monarch waystation at monarchwatch.org. 

[00:23:57] Dr. Lancellotti: Excellent. I’ll have that link posted in the show notes, so that people can figure out how to make themselves a Monarch waystation and help encourage the butterfly population. We’ve planted a bunch of milkweed in our garden about 5 years ago, and every year, we get that milkweed coming back. It’s so fun to see the caterpillars crawl all over the milkweed and the butterflies come down into our patio and enjoy the flowers. One of the things that I’ve really loved is seeing pictures (that you share with us) of the cocoons and your caterpillars as they start to come alive in the summertime.

[00:24:31] Dr. Webb-Milum: It is one of my favorite things. It truly brings me a lot of joy. 

[00:24:35] Dr. Lancellotti: Beautiful. Thank you so much for coming on and sharing all of this information about skin infections with us. These were really helpful episodes, and I’m hoping that people get a lot of information out of them. 

[00:24:48] Dr. Webb-Milum: Thank you so much for having me. 

[00:24:50] Dr. Lancellotti: And for everyone who’s listening, I look forward to your next visit with Your Vet Wants You To Know.

Resources

  1. Banovic, F., Olivry, T., Baumer, W., Paps, J., Stahl, J., Rogers, A., & Jacob, M. (2018). Diluted sodium hypochlorite (bleach) in dogs: antiseptic efficacy, local tolerability and in vitro effect on skin barrier function and inflammation. Vet Dermatol, 29(1), 6-e5. doi:10.1111/vde.12487
  2. Hillier, A., Lloyd, D. H., Weese, J. S., Blondeau, J. M., Boothe, D., Breitschwerdt, E., . . . Sykes, J. E. (2014). Guidelines for the diagnosis and antimicrobial therapy of canine superficial bacterial folliculitis (Antimicrobial Guidelines Working Group of the International Society for Companion Animal Infectious Diseases). Vet Dermatol, 25(3), 163-e143. doi:10.1111/vde.12118
  3. Morris, D. O., Loeffler, A., Davis, M. F., Guardabassi, L., & Weese, J. S. (2017). Recommendations for approaches to meticillin-resistant staphylococcal infections of small animals: diagnosis, therapeutic considerations and preventative measures.: Clinical Consensus Guidelines of the World Association for Veterinary Dermatology. Vet Dermatol, 28(3), 304-e369. doi:10.1111/vde.12444
  4. Mueller, R. S., Bergvall, K., Bensignor, E., & Bond, R. (2012). A review of topical therapy for skin infections with bacteria and yeast. Vet Dermatol, 23(4), 330-341, e362. doi:10.1111/j.1365-3164.2012.01057.x
  5. Summers, J. F., Brodbelt, D. C., Forsythe, P. J., Loeffler, A., & Hendricks, A. (2012). The effectiveness of systemic antimicrobial treatment in canine superficial and deep pyoderma: a systematic review. Vet Dermatol, 23(4), 305-329, e361. doi:10.1111/j.1365-3164.2012.01050.x
  6. Weese, J. S., Giguere, S., Guardabassi, L., Morley, P. S., Papich, M., Ricciuto, D. R., & Sykes, J. E. (2015). ACVIM consensus statement on therapeutic antimicrobial use in animals and antimicrobial resistance. J Vet Intern Med, 29(2), 487-498. doi:10.1111/jvim.12562

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