title: Long term molecular epidemiology of methicillin-susceptible Staphylococcus aureus bacteremia isolates in Sweden.
abstract: Staphylococcus aureus is one of the major pathogens that causes bacteremia; therefore, it is important to understand the long-term molecular epidemiology of S. aureus bacteremia infections. In particular, little is known about the population structure of methicillin-sensitive S. aureus (MSSA) compared to that of methicillin-resistant S. aureus. We investigated potential changes in the MSSA molecular epidemiology in Örebro County, Sweden, from 1980 through 2010. 400 MSSA bacteremia isolates, the first 100 isolated each decade from 1980 through 2010, were retrospectively identified and analyzed regarding assignment to clonal complexes (CCs), presence of virulence genes and antibiotic resistant determinants with DNA microarray-based genotyping. 24 different CCs were identified. Most isolates (80%) belonged to 6 predominant lineages. Of those, the number of isolates assigned to CC5 and CC15 increased, and those assigned to CC8, CC25, and CC30 decreased. The most prevalent clone, CC45, did not show a significant change in prevalence during the study period. A change in prevalence was observed for some of the virulence genes, mainly attributed with their association to certain CCs. With the exception of the common blaZ gene (encoding penicillinase), antibiotic resistance genes were only sporadically detected. In conclusion, the MSSA population structure was genetically diverse. We observed decadal changes in assignments to five predominant clones, and corresponding changes in the prevalence of some virulence genes linked to CC affiliation. In light of the restrictive antibiotics prescriptions and extensive infection control procedures in Sweden, antibiotic resistance genes were rarely detected and their prevalence unaffected during the study period.
authors.affiliation: Department of Infectious Diseases, Örebro University Hospital, Örebro, Sweden; School of Health and Medical Sciences, Örebro University, Örebro, Sweden.
authors.forename: Gunlög
authors.initials: G
authors.lastname: Rasmussen
authors.affiliation: Alere Technologies GmbH, Jena, Germany; Institute for Medical Microbiology and Hygiene, TU Dresden, Dresden, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Monecke
authors.affiliation: Clinical Epidemiology and Biostatistics, Örebro University Hospital, Örebro, Sweden.
authors.forename: Ole
authors.initials: O
authors.lastname: Brus
authors.affiliation: Alere Technologies GmbH, Jena, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Ehricht
authors.affiliation: Department of Infectious Diseases, Örebro University Hospital, Örebro, Sweden; Department of Laboratory Medicine, Clinical Microbiology, Örebro University Hospital, Örebro, Sweden; Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
authors.forename: Bo
authors.initials: B
authors.lastname: Söderquist
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002675:Child, Preschool; D005260:Female; D005838:Genotype; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008712:Methicillin / Q000627:therapeutic use; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D017720:Molecular Epidemiology; D058889:Molecular Typing; D012189:Retrospective Studies; D013203:Staphylococcal Infections / Q000453:epidemiology*; D013548:Sweden
chemical_list: D008712:Methicillin