Abstract
BackgroundStaphylococcus pseudintermedius is the leading cause of pyoderma in dogs and the frequent use of antimicrobial treatment is associated to the development of resistance to nearly all classes of antibiotics. Despite S. pseudintermedius significance, our understanding of the molecular mechanism of β-lactam resistance and its genetic diversity remains limited. We aimed to: i) determine the phenotypic resistance profile of methicillin resistant Staphylococcus pseudintermedius (MRSP) isolated from infected dogs in three different veterinary hospitals in Buenos Aires, Argentina; ii) identify the SCCmec elements and resistance genes; and iii) analyze the clonal relationship between isolates and in regard of dominant lineages found in the world.ResultsIn addition to the differential levels of β-lactam resistance, MRSP isolates (n = 10) showed resistance to 5–6 families of antibiotics, and were therefore categorized as multidrug-resistant. All the isolates were variant of SCCmec V homologous to S. aureus; additional SCCmecFinder analysis classified five of the genomes as SCCmec type V (5C2&5) with mecA (encodes for PBP2a), mecRI and mecI and all the genes closely related to the reference SCCmec type V S. aureus TSGH17 strain. In the remaining five strains, mecA was present, although other genes associated with SCCmec V including mecR1 and mecI were missing. PBP2a was inducible in low level resistance strains (MRSP 8151), and constitutively expressed in MRSP 8150, suggesting different mecA regulatory mechanisms. MRSP isolates showed significant genetic diversity: eight PFGE clonal types and six multilocus-sequence typing (MLST) sequence types (STs) (339, 649, 919, 920, 921 and 922), including four new STs genetically distinct from STs reported in other geographic areas. Comparative genomics and phylogenetic analyses of the MRSP showed a correlation between the genetic content and the phenotypes, and established the genetic relationship between the isolates.ConclusionsMRSP could be a threat to animal health due to it concerning level of antimicrobial resistance. Our study highlights genetic and epidemiological aspects of multidrug-resistant MRSP strains from Argentina showing high degree of correlation between the resistance genes and the phenotype of the isolates and, furthermore, they appeared evolutionary closer to major worldwide reported ST68 and ST71.
Highlights
Staphylococcus pseudintermedius is the leading cause of pyoderma in dogs and the frequent use of antimicrobial treatment is associated to the development of resistance to most classes of antibiotics
This gene is known to reside in a mobile genetic element, a staphylococcal cassette chromosome designated Staphylococcal cassette chromosome (SCCmec) that contains the mec gene complex, mecA and some additional genes, and the cassette chromosome recombinase gene complex, which is responsible for insertion of the SCCmec cassette into the core genome
Antibiotic resistance profiles All the S. pseudintermedius isolates were considered resistant to oxacillin based on the recently revised Clinical and Laboratory Standards Institute (CLSI) breakpoints of S. pseudintermedius, the presence of mecA gene and a SCCmec element
Summary
Staphylococcus pseudintermedius is the leading cause of pyoderma in dogs and the frequent use of antimicrobial treatment is associated to the development of resistance to most classes of antibiotics. The β-lactam resistance of MRSP is due to penicillinbinding protein 2a (PBP2a), a protein encoded by the methicillin resistant gene mecA. This gene is known to reside in a mobile genetic element, a staphylococcal cassette chromosome designated SCCmec that contains the mec gene complex, mecA and some additional genes, and the cassette chromosome recombinase (ccr) gene complex, which is responsible for insertion of the SCCmec cassette into the core genome. As many as thirteen different structural types of SCCmec have been described in S. aureus based on the different combinations of class of mec complexes according to the presence/absence of regulatory genes and insertion sequences, and ccr allotypes (ccrAB and ccrC) [4]. While in S. aureus the structure of SCCmec elements has been shown to be relatively stable, in MRSP the SCCmec elements showed high genetic diversity [4]
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