Today's Veterinary Practice

MAY-JUN 2014

Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.

Issue link: http://todaysveterinarypractice.epubxp.com/i/321264

Contents of this Issue

Navigation

Page 45 of 107

Today's Veterinary Practice May/June 2014 44 DermaTology DeTails Peer reviewed tvpjournal.com P yoderma is a common skin disor- der in small animal practice. Now that the major canine pathogen, Staphylococcus pseudintermedius, has acquired methicillin resistance, treat- ment has become more challenging and more expensive. Keys to success in treat- ment and prevention require: • Prompt identification and treatment of the underlying cause • Use of culture and sensitivity to guide antibiotic use • Increased reliance on topical therapy. WHY ARE DOGS SUSCEPTIBLE TO SKIN INFECTIONS? Of all the species with which we work, dogs seem uniquely predisposed to bacterial skin infections. 1-5 Dogs are more susceptible to skin infections due to basic structural features, such as: • Lack of a follicular lipid plug, which acts like a drain stopper • Fragile skin barrier • Alkaline pH. Table 1 lists underlying skin disor- ders that predispose dogs to staphylococcal skin infec- tions. 6 Dogs with atopic dermatitis are especially suscep- tible due to: • A defective skin barrier, which is represented by the stra- tum corneum and one of the first physical and chemical defenses against microbial infection 7-9 • Potentially decreased levels of defensins—cationic anti- microbial proteins that defend against bacterial infec- tions as part of the innate immune system. 10 WHICH BACTERIA CAUSE PYODERMA IN DOGS? The major canine skin pathogen is S pseudintermedius; 11 however, Staphylococcus schleiferi, Staphylococcus aure- us, and Pseudomonas aeruginosa have also been identi- fied in canine pyoderma. S aureus —a human pathogen— has been identified in a low percent- age of dogs. However, this bacterium has received a great deal of attention due to its methicillin resistance in hu- mans and potential role as a zoonotic agent—dogs infected with methicillin- resistant S aureus (MRSA) most likely acquired the infection from a human. S pseudintermedius , while not as virulent, shares many characteristics with S aureus, in- cluding: • Enzyme and toxin production • Ability to adhere to matrix adhesive proteins • Ability to form biofilms. Methicillin-resistant S pseudintermedius (MRSP) is un- likely to cause human infection, unless a person is very young, very old, or immunocompromised. S schleiferi was first identified from human clinical spec- imens in 1988, and has now been identified as a cause of pyoderma and otitis externa in dogs. 12-14 P aeruginosa —while not common—has been identi- fied on the skin of dogs, particularly in lip fold pyodermas and postgrooming folliculitis. 15,16 Identifying the particular Staphylococcus species in- Valerie A. Fadok, DVM, PhD, Diplomate ACVD North Houston Veterinary Specialists, Spring, Texas TreaTing resisTanT skin infecTions in dogs Table 1. Underlying Disorders in staphylococcal skin infections • atopic dermatitis • other allergic skin conditions • Disorders of keratinization • endocrinopathies • Parasitic diseases A Figure 1. 10-year-old male neutered poodle with atopic dermatitis: Severe gener- alized crusting associated with superficial pyoderma failed to respond to amoxicil- lin–clavulanate and cefpodoxime; culture revealed methicillin-resistant s pseudin- termedius sensitive to amikacin and rifampin (A). Three weeks after topical therapy, consisting of clipping and washing with chlorhexidine and twice daily topical appli- cation of amikacin (5 mg/mL) in Tris EDTA; no systemic antibiotics were used (B). B TVP_2014-0506_DermDetails_Infections.indd 44 5/23/2014 3:24:56 PM

Articles in this issue

Links on this page

Archives of this issue

view archives of Today's Veterinary Practice - MAY-JUN 2014