Journal Scan: Tackling feline eosinophilic plaques with antibiotics

Feline eosinophilic plaques and lip ulcers are representative of a common clinical skin reaction seen in cats termed eosinophilic granuloma complex. As these lesions are prone to erosion and ulceration, secondary bacterial infections are common and likely result in worsening of the lesions.

What they did

The aim of a recent study was to evaluate naturally occurring feline eosinophilic plaques and lip ulcers for secondary infections and to determine the response to antibiotic therapy. By culturing and performing antibiotic susceptibility testing from representative lesions and measuring the lesions before and after antibiotic therapy, the researchers hoped to determine the clinical usefulness of this treatment option. Amoxicillin trihydrate-clavulanate potassium was selected because of its broad-spectrum antimicrobial activity and its efficacy against the normal flora common in feline inflammatory lesions.

Sixteen healthy client-owned cats with confirmed eosinophilic plaques or lip ulcers (nine with plaques and eight with lip ulcers) completed the study. All of the cats had a history of a static condition or a worsening of the condition over several weeks and no history of spontaneous regression of their lesions.

On the first day of the study, a superficial impression smear was examined, and swabs were obtained for aerobic cultures. The cats with each type of lesion were randomly divided into treatment and placebo groups. The cats received a 21-day course of either amoxicillin-clavulanate or placebo. Digital photographs and measurements of the lesions were taken on days 1 and 21 of treatment. On day 21, the cats were reexamined, and a second impression smear of the lesion or previously affected area was taken. There were no adverse reactions to the therapy reported.

What they found


All of the cats' lesions were found to be infected. Coagulase-positive staphylococci were the most frequent isolates.

The cats with eosinophilic plaques responded well to the antibiotic therapy, resulting in a 96.2% reduction in lesion size and an 80% reduction in the microscopic demonstration of bacterial infection. No improvement in these parameters was documented in the placebo group.

The cats with lip ulcers saw a 65% reduction in microscopically identified infection as compared with the placebo group, where no reduction was observed. However, while there was a modest reduction in lip ulcer lesion size for treated cats, as compared with an increase in lesion size for untreated cats, the change was not statistically significant. This disparity in results based on lesion type is not explained in the study design, but the authors hypothesize that increased dosage or treatment duration may be necessary to successfully treat lip ulcers.

Take-home message

The use of amoxicillin-clavulanate was demonstrated to be safe and effective for addressing the secondary bacterial infections associated with feline eosinophilic plaques. These findings substantiate the practice of treating the bacterial infection associated with feline eosinophilic plaques while also addressing the underlying condition.

Wildermuth BE, Griffin CE, Rosenkrantz WS. Response of feline eosinophilic plaques and lip ulcers to amoxicillin trihydrate-clavulanate potassium therapy: a randomized, double-blind placebo-controlled prospective study. Vet Dermatol 2012;23(2):100-e25.

Link to abstract: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3164.2011.01020.x/abstract