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Today's Veterinary Practice May/June 2014 50 | DermaTology DeTails tvpjournal.com • Lipids, such as ceramide complex or phytosphingosine, that help repair the skin barrier when used over time • Emollients that help prevent drying of the skin, which can happen with other products, such as scrubs. Topical antibiotics can be used in some cases to help resolve MRS-associated pyodermas. • Mupirocin topical ointment is effective against most strains of MRSP and can be used to resolve focal lesions. • Topical amikacin spray can be used twice daily in some patients; it can be made by mixing amikacin (5 mg/mL) in Tris-EDTA. This spray is preferable to commercial products containing gentamicin and betamethasone. Note: Betamethasone is a potent steroid that can induce severe cutaneous atrophy if overused; its use should be re- stricted to less than 14 days, particularly on thin skin such as that on the abdomen. Systemic Therapy Not all dogs with MRS will respond to topical therapy, par- ticularly if the infection is severe, generalized, or a deep pyoderma. For these dogs, systemic antibiotic therapy is required, and culture and sensitivity mandatory. Table 2 contains a list of antibiotics, with doses to be considered. Sulfonamides: If the organism is sensitive, potentiated sulfonamides can be used. While side effects are possible, most dogs tolerate these drugs quite well. Sulfamethoxine/ ormetoprim is useful, as it can be administered once daily. Lincosamides: If reported as sensitive, clindamycin can also be used, but only if the bacteria are sensitive to all macrolides. 29 A resistance factor, termed the clindamycin- inducible resistance factor, can be found in Staphylococ- cus species. One indicator that this gene may be present is reported resistance to erythromycin, but sensitivity to clindamycin. Treatment with clindamycin will rapidly in- duce the resistance factor, and antibiotic therapy will fail. Tetracyclines: Although use of tetracyclines is not ad- vocated for most S pseudintermedius infections—because most isolates are resistant to tetracyclines and penicillins— MRSP may revert to tetracycline sensitive. However, consid- ering that tetracycline is no longer available, doxycycline or minocycline may be used instead. However, the break- points for determining sensitivity to doxycycline are chang- ing: if the minimum inhibitory concentration is greater than 0.5 to 1 mcg/mL, then failure of therapy is more likely even if a culture indicates sensitivity. 30 The majority of MRSP are sensitive to chloramphenicol, rifampin, and amikacin: Amphenicols: Chloramphenicol must be given at 30 to 50 mg/kg Q 8 H, which can result in poor compliance. • After 30 days of treatment, most dogs become nauseated or develop vomiting and diarrhea, and some dogs devel- op a poorly understood hindlimb paresis that resolves upon cessation of antibiotic use. • Chloramphenicol is a health risk for humans, with the potential to induce aplastic anemia. If dispensed to cli- ents, advise clients to handle the medication carefully. Aminoglycosides: Amikacin is well tolerated by most dogs but must be given by subcutaneous injection (15 mg/ kg once daily) and does present the risk for renal toxicity. • Frequent monitoring of urine for casts and repeated blood analysis of blood urea nitrogen (BUN) and creati- nine can make this an expensive option. • For a healthy dog, weekly urinalysis can evaluate cast formation, proteinuria, and a drop in specific gravity. • Urinalysis is more sensitive than BUN or creatinine to amikacin-induced renal toxicosis. Rifamycins: Rifampin can be used as monotherapy for staphylococcal infections, but can be hepatotoxic; there- fore, monitoring liver enzymes is important. Side effects can be minimized if the daily dosage is kept at 10 mg/kg/ day or less. • In an otherwise healthy dog, blood analysis should occur before administration, then 10 to 14 days into therapy. • Owners should be warned to stop administration if dogs have any loss of appetite or vomiting. • Urine may look red or orange due to the drug's color, but is not a reason to stop therapy. IN SUMMARY Pyoderma management in the age of methicillin resistance is an ongoing challenge in veterinary medicine. My mani- festo for pyoderma is to: 1. Utilize frequent bathing with chlorhexidine sham- poos and/or other topicals instead of systemic antibiot- ics whenever possible. 2. Be aggressive when systemic antibiotics are required, treating with the appropriate dose until the pyoderma is completely resolved. Always combine systemic antibiot- ics with topical therapy. 3. Avoid empirical use of fluoroquinolones for staphy- lococcal pyodermas. Fluoroquinolones, particularly the early generations, are more effective against gram nega- tive bacteria than gram positive bacteria. 4. Utilize topical therapy to prevent recurrence. 5. Diagnose and treat the underlying cause. A very useful resource for current information about MRS, particularly zoonotic potential, is the Worms and Germs blog, coordinated by Dr. Scott Weese and Dr. Maureen Anderson (wormsandgermsblog.com/promo/services). At this site, you can download PDF files for your clients that explain these infections and how to handle them. n bog = bacterial overgrowth syndrome; bUn = blood urea nitrogen; mrs = methicillin-resistant Staphylococci; mrsa = methicillin-resistant S aureus; mrsP = methicillin- resistant S pseudintermedius; mssP = methicillin- susceptible S pseudintermedius Valerie Fadok, DVM, PhD, Diplomate ACVD, is a dermatology specialist at North Houston Veterinary Specialists in Spring, Texas. She has lectured internationally on veterinary skin diseases and is currently a derma- tology consultant on the Veterinary In- formation Network (VIN). She received her DVM from Washington State University and her PhD in experimen- tal pathology from Unversity of Colorado. TVP_2014-0506_DermDetails_Infections.indd 50 5/23/2014 3:24:58 PM