This webappendix, part of the original submission and peer-reviewed, provides supplementary figures and tables to support the study by García-Álvarez et al. (2011) on the emergence of methicillin-resistant *Staphylococcus aureus* (MRSA) with a novel *mecA* homologue in human and bovine populations in the UK and Denmark. The supplementary content includes: 1. **Supplementary Figures:** - **Figure S1:** A diagram illustrating the alignment of six different PCR primers with the matching sections of the gene nucleotide sequence of the *mecA* from LGA251 and MRSA252. - **Figure S2:** Antimicrobial phenotypic results for *Staphylococcus aureus* strain LGA251, showing the antimicrobial susceptibility testing under British Society for Antimicrobial Chemotherapy (BSAC) guidelines. - **Figure S3:** Phylogenetic relationships of MecA homologues from various *S. aureus* strains and related species. - **Figure S4:** Geographical distribution of human MRSA strains carrying the novel *mecA* gene in Scotland, indicating the approximate locations of isolates. - **Figure S5:** Geographical distribution of human MRSA strains carrying the novel *mecA* gene in Denmark, showing the locations of isolates and their lineage based on spa typing and/or multi-locus sequence type (MLST). - **Figure S6:** Phylogenetic tree comparing multi-locus sequence types (STs) of *Staphylococcus aureus*, including the most frequently reported STs and those carrying the *mecA_LGA251* homologue. 2. **Supplementary Tables:** - **Table S1:** Details of the sequence of events concerning the discovery of the *mecA_LGA251* gene and the search for isolates possessing SCC*mec_LGA251*. - **Table S2:** Best matching proteins for the nucleotide coding sequences (CDS) identified within the novel SCC*mec* type XI, providing information on similarity percentages and alignment lengths. These supplementary materials enhance the understanding of the study's findings and provide additional context and data supporting the research.This webappendix, part of the original submission and peer-reviewed, provides supplementary figures and tables to support the study by García-Álvarez et al. (2011) on the emergence of methicillin-resistant *Staphylococcus aureus* (MRSA) with a novel *mecA* homologue in human and bovine populations in the UK and Denmark. The supplementary content includes: 1. **Supplementary Figures:** - **Figure S1:** A diagram illustrating the alignment of six different PCR primers with the matching sections of the gene nucleotide sequence of the *mecA* from LGA251 and MRSA252. - **Figure S2:** Antimicrobial phenotypic results for *Staphylococcus aureus* strain LGA251, showing the antimicrobial susceptibility testing under British Society for Antimicrobial Chemotherapy (BSAC) guidelines. - **Figure S3:** Phylogenetic relationships of MecA homologues from various *S. aureus* strains and related species. - **Figure S4:** Geographical distribution of human MRSA strains carrying the novel *mecA* gene in Scotland, indicating the approximate locations of isolates. - **Figure S5:** Geographical distribution of human MRSA strains carrying the novel *mecA* gene in Denmark, showing the locations of isolates and their lineage based on spa typing and/or multi-locus sequence type (MLST). - **Figure S6:** Phylogenetic tree comparing multi-locus sequence types (STs) of *Staphylococcus aureus*, including the most frequently reported STs and those carrying the *mecA_LGA251* homologue. 2. **Supplementary Tables:** - **Table S1:** Details of the sequence of events concerning the discovery of the *mecA_LGA251* gene and the search for isolates possessing SCC*mec_LGA251*. - **Table S2:** Best matching proteins for the nucleotide coding sequences (CDS) identified within the novel SCC*mec* type XI, providing information on similarity percentages and alignment lengths. These supplementary materials enhance the understanding of the study's findings and provide additional context and data supporting the research.