Frequent Dissemination and Carriage of an SCCmec-mecC Hybrid in Methicillin-resistant Mammaliicoccus Sciuri in Farm Animals from Tunisia

Objectives: In this study, we aimed to assess the extent of dissemination of methicillin-resistant Mammaliicoccus sciuri in animal farms in Tunisia and evaluate the distribution of virulence and methicillin resistance genes in the M. sciuri population.

Methods: Staphylococci and mammaliicocci isolated from unhealthy animals and healthy humans from adjacent farms in Tunisia were characterized for antimicrobial susceptibility, biofilm formation, agglutination, and hemolysis abilities. Mammaliicoccus sciuri relatedness and content in antibiotic resistance and virulence genes were analyzed by whole-genome sequencing (WGS).

Results: Mammaliicoccus sciuri was the most prevalent species (46.2%), showing the highest resistance rates to fusidic acid (94.6%), oxacillin (73%), penicillin (40.5%), clindamycin (37%), ciprofloxacin (27%), and cefoxitin (24.3%). Some isolates carried genes encoding resistance to nine different antibiotic classes. mecA was found in 35% of M. sciuri and mecC in 16.2%. All isolates carrying mecC were of S. sciuri subspecies carnaticus and carried the hybrid element SCCmec-mecC. Mammaliicoccus sciuri were able to produce strong biofilm (27%) and have clumping ability (16%). Additionally, they carried genes for capsule production (cap8, 100%), iron-regulated surface determinants (isdE, 24%; isdG, 3%), and virulence regulation (clpC and clpP, 100%). Single nucleotide polymorphisms (SNPs) analysis showed that 17 M. sciuri cross-transmission events probably occurred between different animal species and farms. Moreover, SCCmec was estimated to have been acquired five times by S. sciuri subsp. carnaticus.

Conclusion: Multidrug resistant and pathogenic M. sciuri were frequently disseminated between different animal species within the farm environment. mecA and mecC can be disseminated by both frequent acquisition of the SCCmec element and clonal dissemination.