Abstract
Resin acids are valued in traditional medicine for their antiseptic properties. Among these, abietic acid has been reported to be active against methicillin-resistant Staphylococcus aureus (MRSA) strains. In veterinary healthcare, the methicillin-resistant Staphylococcus pseudintermedius (MRSP) strain is an important reservoir of antibiotic resistance genes including mecA. The incidence of MRSP has been increasing, and treatment options in veterinary medicine are partial. Here, we investigated the antimicrobial and antibiofilm properties of abietic acid against three MRSP and two methicillin-susceptible Staphylococcus pseudintermedius (MSSP) strains, isolated from diseased pet animals and human wound samples. Abietic acid showed a significant minimal inhibitory concentration (MIC) value ranging from 32 to 64 μg/mL (MRSPs) and 8 μg/mL (MSSP). By checkerboard method we demonstrated that abietic acid increased oxacillin susceptibility of MRSP strains, thus showing a synergistic interaction with oxacillin. Abietic acid was also able to contrast the vitality of treated MSSP and MRSP1 biofilms at 20 μg/mL and 40 μg/mL, respectively. Finally, the compound moderately reduced mecA, mecR1 and mec1 gene expression. In conclusion, the results here reported demonstrate the antimicrobial activity of abietic acid against MRSP and support the use of this compound as a potential therapeutic agent to be used in combinatorial antibiotic therapy.
Highlights
Staphylococcus pseudintermedius is a normal inhabitant of the skin and mucosa of healthy dogs and cats
We investigate the synergistic interaction between abietic acid and oxacillin against methicillin-resistant Staphylococcus pseudintermedius (MRSP) strains
To get a better understanding of antimicrobial activity of abietic acid against MRSP, we examined the interaction between abietic acid and oxacillin via the checkerboard method and described it in terms of fractional inhibitory concentration (FIC)
Summary
Staphylococcus pseudintermedius is a normal inhabitant of the skin and mucosa of healthy dogs and cats. The spread of methicillin-resistant Staphylococcus pseudintermedius (MRSP) worldwide represents a health problem for both companion animals and humans since zoonotic transmission has been documented [2,3]. Since mec gene is located on a mobile element of the chromosome it can be transferred between staphylococcal species. Stefanetti et al demonstrated that up to 96% of S. pseudintermedius strains isolated from canine infections were able to produce biofilm [6]. Meroni et al reported that 68% of S. pseudintermedius isolates were able to form biofilms, but 100% of the multidrug resistant strains were slime producers; it seems that biofilm production can facilitate bacteria horizontal gene transfer [8]. Discovery of novel agents for treatment of MRSP-associated and biofilm related infections is highly warranted
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