Clonal relatedness of coagulase-positive staphylococci among dogs-owning households in Spain. Detection of multidrug-resistant-MSSA-CC398 and novel point mutations in 23S rDNA of MRSA-CC5-SCCmec type-IV2B

Nasal carriage of coagulase-positive staphylococci (CoPS) in healthy dogs could indicate increased risks of colonization for in-contact people or vice versa. This study determined the nasal carriage rate of CoPS among healthy dogs and in-contact people, their genotypic characteristics and phylogenetic relatedness. Nasal samples were collected from 27 households (34 dogs and 41 humans) in Spain. Staphylococci were identified by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry, and their antimicrobial resistance (AMR) genes were tested by PCR/sequencing. The relatedness of CoPS from the same households was assessed by core genome single nucleotide polymorphisms (SNPs) analyses. Staphylococcus aureus (S. aureus) carriage was found in 34.1% of humans (including one methicillin-resistant S. aureus (MRSA-CC5-t2220-SCCmec type-IV2B) and 5.9% of dogs; Staphylococcus pseudintermedius in 2.4% of humans and 32.4% of dogs; while Staphylococcus coagulans was only detected in dogs (5.4%). Remarkably, one human co-carried S. aureus/S. pseudintermedius, while a dog co-carried the three CoPS species. Household density was significantly associated with S. aureus carriage in humans and dogs (OR=10.11, 95% CI: 1.59-64.01, p=0.014). Closely related (<15 SNPs) S. aureus or S. pseudintermedius isolates were found in humans or dogs in 3 households. Ten clonal complexes (CCs) were detected among the S. aureus isolates, of which Methicillin-susceptible S. aureus-CC398-IEC-type C (t1451 and t571) was the most frequent, but exclusive to humans. S. aureus and S. pseudintermedius isolates harboured resistomes to beta-lactams (blaZ, mecA), macrolides (ermB, ermT, linA, mphC, msrA), aminoglycosides (aac6-aph2, ant4), tetracyclines (tet(K), tet(M)), fluoroquinolones (amino acid changes in grlA and gyrA), sulfonamides (dfrA, dfrD, dfrG, dfrK), monoxylcarbolate (mupA), florfenicol (catA), and linezolid (G2261A & T1584A point mutations in 23S rDNA). The S. coagulans isolates were susceptible to all antimicrobials. Most of the S. pseudintermedius isolates carried lukS/F-I, siet, sient genes, but all S. aureus isolates were negative for lukS/F-PV, tst-1, eta and etb genes. All MRSA isolates were multidrug-resistant by phenotype, as were 20.0% of the MSSA and 31.7% of the Methicillin-susceptible S. pseudintermedius (MSSP). Clonally related human-to-human MSSA and dog-to-human MSSP were found. The detection of the MSSA-CC398 clade suggests the need for its continuous surveillance from One Health perspective.