Methicillin-Resistant Staphylococcus aureus/genetics; Methicillin-Resistant Staphylococcus aureus/pathogenicity; Staphylococcal Infections/epidemiology; Staphylococcus aureus/genetics; Staphylococcus aureus/pathogenicity; Adolescent; Adult; Aged; Anti-Bacterial Agents/pharmacology; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Bacterial Toxins/genetics; Bacterial Toxins/isolation & purification; Bacterial Typing Techniques; Carrier State/epidemiology; Child; Child, Preschool; DNA, Bacterial/genetics; Drug Resistance, Multiple, Bacterial/genetics; Enterotoxins/genetics; Enterotoxins/isolation & purification; Female; Genes, Bacterial; Genetic Variation; Genotype; Humans; Infant; Male; Methicillin-Resistant Staphylococcus aureus/drug effects; Methicillin-Resistant Staphylococcus aureus/isolation & purification; Microbial Sensitivity Tests; Middle Aged; Phenotype; Prevalence; Sequence Analysis, DNA; Spain/epidemiology; Staphylococcal Infections/metabolism; Staphylococcus aureus/drug effects; Staphylococcus aureus/isolation & purification; Superantigens/genetics; Superantigens/isolation & purification; Virulence; Virulence Factors/genetics; Young Adult; beta-Lactams/metabolism