When topical treatment for pyoderma fails

Photo: Soloviova Liudmyla/Adobe Stock

If topical therapy for the treatment of pyoderma is not successful, the next step is empirical systemic treatment, according Jason B. Pieper, DVM, MS, DACVD, assistant professor at Iowa State University. According to his lecture Updates in pyoderma: diagnosis and treatment, presented at the 2025 Veterinary Meeting & Expo (VMX) in Orlando, Florida, systemic antibiotics are no longer the recommended first treatment of choice due to the rise in antimicrobial resistance and awareness. However, in cases where topicals have failed or cannot be used to treat a patient’s infection, systemic treatment is the next treatment of choice, followed by bacterial culture and susceptibility.¹

Recommendations for systemic treatment of pyoderma in Veterinary Dermatology’s 2014 “Guidelines for the diagnosis and antimicrobial therapy of canine superficial bacterial folliculitis” shows 3 tiers of systemic antimicrobial treatment options for pyoderma in dogs.^1,2

The first tier is the primary choice of therapy of known or suspected pyoderma. For this tier, clindamycin or lincomycin is recommended. First generation cephalosporins (such as cefalexin, cefadroxil) and amoxicillin-clavulanate is also suggested, as well as trimethoprim- and ormetoprim-potential sulphonamides.²

In the first or second tier, third generation cephalosporins (cefovecin, cefpodoxime) are suggested. “There is insufficient evidence for this working group to reach consensus on categorization of these agents as first or second tier drugs…and concerns about selection of ESBL [extended-spectrum beta-lactamase]-producing Escherichia coli),” wrote the organization in its guidelines.²

In the second tier, doxycycline or minocycline; chloramphenicol; fluoroquinolones (such as enrofloxacin, marbofloxacin, orbifloxacin, pradofloxacin and ciprofloxacin, which should only be used when other options are not available); rifampicin; and aminoglycosides, including gentamicin and amikacin are the suggested antimicrobial drugs.²

Additionally, first tier antimicrobial drugs (clindamycin, lincomycin and potentiated sulphonamides) can be “considered when cultures indicate susceptibility,” according to the document.^1,2

The third tier, which consists of linezolid, teicoplanin, and vancomycin, is only reserved for when the first 2 tiers are “not appropriate and cultures indicate susceptibility,” wrote the authors of the 2014 guidelines. “Regardless of the fact that most (or all) MRSP [methicillin-resistant Staphylococcus pseudintermedius] are susceptible, the use of these three [antimicrobial drugs] is strongly discouraged. These drugs can be considered ‘reserved for the treatment of serious MRSA infections in humans,’” they continued.²

“Realistically, the way I look at for these 3 down here, if you have a superficial pyoderma, you’d never need these,” said Pieper of the drugs in the third tier.¹ “You can treat it topically and get rid of it otherwise.”

Upcoming updates to the guidelines

According to Pieper, new updates to the 2014 guidelines, based on a meeting in July 2024, are in the process of being written. The updated document has not been finalized yet.¹

However, based on what was presented in the July 2024 meeting, the first tier will only involve cephalexin, clindamycin, and clavamox. The second tier will consist of third generation cephalosporins, fluoroquinolones, tetracyclines, and sulfas.

The next group is being called a “Reserved” group, and will comprise rifampin, aminoglycoside, and chloramphenicol. “The important aspect of this though is you [have] to discuss the adverse effects with the owners, prognosis, and implement a plan to address the underlying disease, because the biggest concern is that this infection comes back again and again. If they were only susceptible to this previously, there's a potential it could be resistant to these now, and you're really going to be in trouble, you know, down the line for that,” emphasized Pieper.

“So again, still based off of empirical for first tier; second tier is culture, and then third is culture if you have no other options, more or less, kind of going down those lines,” he continued. “So that's kind of how it's currently broken down, is going to be written and going out soon.”

Next steps

Following a recheck—which is a crucial step—if the infection is not responsive to empirical systemic treatment, the next step would be to perform a bacterial culture and susceptibility, according to Pieper. This step involves identifying the organism the patient has and finding the appropriate antibiotic to treat it. A culture should be done when¹:

1. There is less than a 50% reduction in lesions within 2 weeks of appropriate systemic antimicrobial therapy.
2. New lesions appear 2 weeks or more after beginning the appropriate antimicrobial drug therapy.
3. There is a presence of residual superficial pyoderma lesions after 6 weeks of antimicrobial therapy along with the presence of cocci on cytology.
4. Intracellular rod-shaped bacteria are found on cytology. “The reason why we actually state this though here…is because the rods, we can't predict the susceptibility as easily as we can with staph. Staph is pretty repeatable, we kind of have a good idea. And that's why the first tier is what the first tier is, because historically, it's been shown to be relatively effective in a large majority of staph organisms,” said Pieper.
5. The canine patient or a pet from the same household as the affected patient has a history of multi-drug resistance infection. “These dogs can actually be be positive carriers for this resistant organism up to a year afterwards,” explained Pieper. “And actually, even dogs that were not even affected, you know, household dogs, they have actually been shown to be positive for carriers afterwards, too, in two-thirds of the dogs”

Takeaway

When topical treatments for pyoderma fail, empirical systemic therapy should follow. If the infection continues to be unresponsive to empirical systemic therapy, bacterial culture and susceptibility testing should be performed to identify the specific pathogen and guide the choice of antibiotics.

References

1. Pieper JB. Updates in pyoderma: Diagnosis and treatment. Presented at: Veterinary Meeting & Expo; Orlando, FL. January 25-29, 2025.
2. Hillier A, Lloyd DH, Weese JS, et al. 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). Veterinary Dermatology. 2014;25(3):163. doi:10.1111/vde.12118