Topical Only: How Clinicians Cleared a Drug-Resistant Skin

It sounds like the setup to a nightmare case: an immunocompromised cat on long-term prednisolone and cyclosporine develops a skin infection that cultures out methicillin-resistant Staphylococcus pseudintermedius — resistant to virtually every oral antibiotic you have. The remaining systemic options are vancomycin and amikacin. What do you do?

A new case report published in Frontiers in Veterinary Science offers an answer worth knowing, and it's more straightforward than you might expect.

The Patient

An 8-year-old spayed female Abyssinian cat presented with progressive pruritic skin lesions affecting the pinnae, ventral thorax, and inguinal region after two months of failed empirical treatment elsewhere. Her workup was sobering: hematocrit of 13.3%, leukocytosis, hypoalbuminemia, and a serum amyloid A of over 100 mg/L. Cytology showed acantholytic keratinocytes alongside intracellular cocci. Histopathology confirmed pemphigus foliaceus (PF) with secondary bacterial infection.

She was started on prednisolone, cyclosporine, amoxicillin-clavulanic acid, and a topical steroid-antimicrobial cream (betamethasone/clotrimazole/gentamicin), with 2% chlorhexidine and 10% povidone-iodine antiseptic cleansing twice daily.

When the Culture Came Back

Initial culture from the left inguinal region grew Staphylococcus aureus — susceptible, manageable. But at the four-week recheck, a worsening lesion in the right inguinal region cultured out MRSP. The susceptibility profile was brutal: resistant to amoxicillin-clavulanic acid, cephalosporins, clindamycin, enrofloxacin, doxycycline, imipenem, azithromycin, and oxacillin. The only systemic options remaining were amikacin and vancomycin.

Here's where the clinical decision gets interesting. The authors noted the infection was localized and superficial, with no evidence of systemic involvement. Intravenous vancomycin was considered and deferred. Instead of escalating, they doubled down on topical therapy: the oral amoxicillin-clavulanic acid was discontinued, systemic antibiotics were not added, and strict adherence to the chlorhexidine and povidone-iodine protocol was reinforced. Topical gentamicin cream was continued for local antimicrobial coverage.

What Happened

It worked. The lesions resolved completely. Subsequent culture from the previously affected site grew Moraxella osloensis, interpreted as superficial recolonization rather than active infection — no MRSP detected. The cat went on to complete eight months of immunosuppressive therapy, which was then successfully tapered and discontinued. At one-year telephone follow-up, the owner reported the cat remained clinically normal with no recurrence.

Why This Matters

MRSP is typically thought of as a canine problem, but it's increasingly showing up in feline patients — and when it does, the resistance profiles can be severe. This case report highlights the emerging clinical relevance of MRSP in cats receiving immunosuppressive therapy, where disrupted skin barrier function and impaired immune defenses create conditions for resistant opportunistic infections. nih

The stewardship argument here is real and worth internalizing. Reaching for vancomycin in a cat with a localized, superficial skin infection — however scary the culture result looks — may not be necessary or appropriate. Topical antiseptics achieve high local drug concentrations without driving systemic resistance, and the existing evidence from canine dermatology supports chlorhexidine-based protocols as effective against methicillin-resistant staphylococcal infections when lesions are focal and compliance is achievable.

The authors are careful to note the limits of this case: the two cultures came from different lesions at different time points, so the apparent shift from S. aureus to MRSP may reflect lesion-to-lesion variation rather than a true species change. Owner compliance with follow-up visits was inconsistent. And the efficacy of individual components of the topical regimen — chlorhexidine vs. povidone-iodine vs. gentamicin cream — cannot be teased apart from this single case.

None of that changes the core takeaway.

The Clinical Bottom Line

Not every MRSP culture demands a last-resort antibiotic. In a cat with localized, superficial pyoderma and no systemic signs of infection, a well-executed topical regimen may be not just adequate but the right call — for the patient, for the human-animal bond (no IV hospitalization), and for antimicrobial stewardship. This case gives you a documented example of that approach succeeding in one of the hardest populations: an immunocompromised cat on dual immunosuppression.

Assess the lesion distribution. Assess the systemic picture. Then decide whether you're actually looking at a topical problem dressed up as a systemic one.

Park SW, Kim K, Ro WB, Lee CM. Case Report: Resolution of a cutaneous infection with methicillin-resistant Staphylococcus pseudintermedius with topical therapy in a cat with pemphigus foliaceus. Front Vet Sci. 2026 Apr 17;13:1822252. doi: 10.3389/fvets.2026.1822252