Topical Antimicrobial Therapy with Fusidic Acid

In the Literature

Frosini SM, Bond R, Loeffler A, Larner J. Opportunities for topical antimicrobial therapy: permeation of canine skin by fusidic acid. BMC Vet Res. 2017;13(1):345.

The Research …

Increased isolation of resistant organisms from skin infections—particularly methicillin-resistant Staphylococcus pseudintermedius and other staphylococci—in veterinary patients is resulting in intensified concern due to the potential impact of these organisms in both veterinary and human medicine.¹ This concern has led to several studies evaluating topical therapeutic options for superficial infections in companion animals with the goal of decreasing the chance for development of resistance.

This in vitro study aimed to determine the depth of penetration of fusidic acid (FA) in canine skin. FA is a lipophilic antibiotic with activity against coagulase-positive staphylococci, including methicillin-resistant S pseudintermedius. Skin biopsy samples were obtained from the dorsum and groin of canine cadavers to evaluate body regions with different hair follicle density. The samples were either left untreated or repeatedly tape-stripped to mimic skin damage often seen with inflammatory skin disease. Skin samples were assembled into Franz diffusion cells, and a 10-mg/g FA suspension was applied to the surface. After 24 hours, receptor fluid and cryosectioned skin samples from various depths were evaluated for FA concentration. FA was detected only in samples in which the follicular infundibulum and more superficial structures (eg, surface epidermis, hairs) were present. The antibiotic did not penetrate past the isthmus of the hair follicle, thus supporting the potential use of FA for the treatment of both surface and superficial bacterial infections in dogs.

… The Takeaways

Key pearls to put into practice:

• Although FA appears to be a viable treatment option for surface and superficial bacterial skin infections in dogs, this antibiotic is not currently available in any formulations in the United States for either human or veterinary use.

• Due to the concern about increased isolation of resistant organisms from bacterial skin infections in veterinary patients, clinicians are encouraged to employ appropriate antimicrobial stewardship when recommending specific therapy.²

• Increased use of topical antimicrobial therapy in veterinary patients may help decrease the chance for development of resistance. Bacteria are less likely to develop resistance to an antiseptic (eg, chlorhexidine, sodium hypochlorite) than to an antibiotic. Continued evaluation of novel antimicrobial agents will likely remain a focus in veterinary dermatology in the coming years.