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In vitro activity of fusidic acid and mupirocin against coagulase-positive staphylococci from pets
A Loeffler1, S J Baines, M S Toleman
1Department of Veterinary Clinical Sciences, Royal Veterinary College, Hawkshead Lane, North Mymms, Hatfield, Hertfordshire AL9 7TA, UK.
Objectives:
Methicillin-resistant Staphylococcus aureus (MRSA) and multiresistant Staphylococcus pseudintermedius (MRSP) have emerged as important pathogens in animal infections. Associated therapeutic problems and the zoonotic potential of staphylococci have renewed interest in topical antibiotics for treatment and carrier decolonization. Fusidic acid and mupirocin are used topically in humans and animals but resistant strains isolated from people are increasing. This study investigates the in vitro activity of fusidic acid and mupirocin against coagulase-positive staphylococci from pets.
Methods:
A collection of 287 staphylococci was examined, comprising 102 MRSA, 102 methicillin-susceptible S. aureus, 71 S. pseudintermedius and 12 MRSP from canine and feline infections and carrier sites isolated in the UK and Germany. MICs were determined by the agar dilution method according to CLSI (formerly NCCLS) standards.
Results:
The majority (89.7%) of all MICs were
Conclusions:
In all but seven MRSA isolates, MICs were below the concentrations achievable experimentally at application sites suggesting therapeutic efficacy of both antibiotics in infections involving multiresistant staphylococci and for decolonization of carriers. However, the seven MRSA with high MICs, all of the dominant UK human hospital lineages, highlight the importance of monitoring treatment success as resistant strains may occur in animals.
Insights
Fusidic acid and mupirocin show in vitro efficacy against most pet staphylococci, including MRSP. However, seven MRSA isolates exhibited high MICs, underscoring the need for monitoring treatment success in animals.
Area of Science:
- Veterinary Microbiology
- Antimicrobial Resistance
- Zoonotic Diseases
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) and multiresistant Staphylococcus pseudintermedius (MRSP) are significant animal pathogens.
- Increasing resistance in human staphylococci necessitates evaluating topical antibiotics like fusidic acid and mupirocin for animal use.
- The zoonotic potential of staphylococci drives interest in decolonization strategies.
Purpose of the Study:
- To assess the in vitro activity of fusidic acid and mupirocin against coagulase-positive staphylococci isolated from pets.
- To compare antibiotic susceptibility between staphylococci from infection sites and carrier sites.
Main Methods:
- Analyzed 287 staphylococcal isolates (MRSA, MSSA, MRSP, S. pseudintermedius) from canine and feline infections/carriers in the UK and Germany.
- Determined Minimum Inhibitory Concentrations (MICs) using the agar dilution method per CLSI standards.
Main Results:
- Most isolates (89.7%) had MICs ≤0.25 mg/L for both antibiotics.
- All MRSP isolates showed MICs ≤2 mg/L.
- Seven MRSA isolates displayed high MICs (up to 1024 mg/L for fusidic acid, 16 mg/L for mupirocin).
- Infection isolates had significantly higher MICs than carriage isolates (P ≤0.001).
Conclusions:
- Fusidic acid and mupirocin demonstrate potential therapeutic efficacy against multiresistant staphylococci in pets.
- High MICs in seven MRSA isolates, linked to human hospital lineages, highlight the risk of emerging resistance in animals.
- Monitoring treatment outcomes is crucial to detect and manage resistant staphylococcal strains in veterinary medicine.
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