The Paw-fect prescription: Antimicrobials for staphylococcal infections in small animals

Staphylococcal infections are one of the most common bacterial infections found in small animal dermatology. These infections can cause a wide range of clinical signs, from mild skin irritation to severe pyoderma.

Researchers from North Carolina State University revised previous recommendations and further expounded on the most antimicrobial selection and its efficacy in their April 2023 issue of the Journal of American Veterinary Medical Association.¹ The study analyzed the efficacy of different antimicrobial agents commonly used in small animal dermatology to treat staphylococcal infections.

The study found that first-generation cephalosporins, amoxicillin-clavulanate, and clindamycin (in no particular order) were first-choice antibiotics and effective. However, due to the emergence of antibiotic-resistant strains of Staphylococcus, the use of these drugs is becoming limited. The researchers then examined alternative antibiotics.

The FDA has not approved tetracyclines for animals, but veterinarians can legally prescribe them extra label using human generic forms. Testing has now become more accurate with a veterinarian-specific susceptibility breakpoint, whereas previously it reported poor efficacy. Aminoglycosides such as gentamicin and amikacin have in vitro activity against Staphylococcus and methicillin-resistant staphylococcus species (MRSP) creates disadvantages of daily injection doses and risk for kidney injury as a deterrent. In the presence of pus and cellular debris, gentamicin and amikacin are deemed useless.

The incidence of methicillin-resistant staphylococcus species has been on the uptrend and continues to increase. Drugs such as chloramphenicol, tetracycline, and aminoglycosides are drugs to consider for MRSP only if a susceptibility test can confirm activity.

• Vancomycin is not ideal due to its difficulty to administer.
• Linezolid’s downfall is cost, while it is well tolerated.
• Rifampin has been an effective treatment for canine pyoderma at a dose of 5mg/kg once daily for 10 days. To avoid adverse effects, it is recommended not to exceed 10mg/kg/day and monitor liver enzymes and bilirubin during treatment.
• Veterinarians who aim to limit systemic antibiotics can consider topicals and disinfectants can be considered for superficial pyoderma.

The researchers conducting the study recommend that clinicians consider using first-choice antibiotics to treat staphylococcal infections.¹ Particularly in cases where antibiotic resistance is a concern, they should use susceptibility testing to make appropriate choices. Those medications that are consistently active against methicillin-resistant strains are discouraged due to its importance in human medicine and must be used responsibly. The use of topical antimicrobial agents can also be effective in treating localized infections, and a combination of systemic and topical therapy may be necessary for recurrent infections.

Dehaney is a 2023 PharmD candidate at the University of Connecticut

Reference

Papich MG. Antimicrobial agents in small animal dermatology for treating staphylococcal infections. J Am Vet Med Assoc. Published online 2023:1-10. doi:10.2460/javma.23.01.0023