Clonal Relatedness of Coagulase-positive Staphylococci Among Healthy Dogs and Dog-owners in Spain. Detection of Multidrug-resistant-MSSA-CC398 and Novel Linezolid-resistant-MRSA-CC5

Introduction: 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.

Methods: Nasal samples were collected from 27 households (34 dogs and 41 humans) in Spain. Staphylococci were identified by MALDI-TOF-MS, their antimicrobial resistance (AMR) genes and -types were tested by PCR/sequencing. The relatedness of CoPS from the same households was assessed by core genome single nucleotide polymorphisms (SNPs) analyses.

Results: carriage was found in 34.1% of humans (including one methicillin-resistant MRSA-CC5-t2220-SCC type-IV2B) and 5.9% of dogs; in 2.4% of humans and 32.4% of dogs; while was only detected in dogs (5.4%). Remarkably, one human co-carried /, while a dog co-carried the three CoPS species. Household density was significantly associated with carriage in households with > than 1 dog and >than 1 human (OR = 18.10, 95% CI: 1.24-260.93,  = 0.034). Closely related (<15 SNPs) or were found in humans or dogs in three households. About 56.3% carriers (dog or human) harboured diverse within-host -types or AMR genotypes. Ten clonal complexes (CCs) were detected among the , of which methicillin-susceptible -CC398-IEC-type C (t1451 and t571) was the most frequent, but exclusive to humans. and isolates harboured resistance genes or mutations associated to 9 classes of antimicrobials including linezolid (G2261A & T1584A point mutations in 23S rDNA). The isolates were susceptible to all antimicrobials. Most of the carried and genes, and all were negative for -PV and genes.

Discussion: Clonally related human-to-human MSSA and dog-to-human MSSP were found. The detection of the MSSA-CC398 clade highlights the need for its continuous surveillance from One Health perspective.