title: Methicillin-resistant Staphylococcus aureus in Stockholm, Sweden: Molecular epidemiology and antimicrobial susceptibilities to ceftaroline, linezolid, mupirocin and vancomycin in 2014.
abstract: Methicillin-resistant Staphylococcus aureus (MRSA) is a public health problem worldwide. The aim of the present study was to investigate the molecular epidemiology and antimicrobial susceptibilities of MRSA strains in Stockholm, Sweden in 2014. Pulsed-field gel electrophoresis (PFGE) was used to characterise the strains. Antimicrobial susceptibilities to ceftaroline, linezolid and mupirocin were determined by the disc diffusion method. Etest was used to determine vancomycin susceptibility and to confirm resistance to ceftaroline, mupirocin and linezolid in non-susceptible strains. High-level ceftaroline-resistant strains [minimum inhibitory concentration (MIC)≥4mg/L] were confirmed by the broth microdilution method. spa typing was carried out on strains that were non-susceptible to the antibiotics tested. In total, 743 consecutive non-duplicate MRSA strains recovered in Stockholm in 2014 were investigated. PFGE analysis of the isolates revealed a population with 271 different PFGE patterns and three non-typeable strains. No PFGE type accounted for >10% of all strains. The most common PFGE types were MRSA-00-02 (6.9%) and MRSA-05-02 (4.6%). MRSA-05-02 is a USA300-like strain. The antimicrobial susceptibilities of the strains were as follows: ceftaroline, 98.5%; linezolid, 100%; mupirocin, 99.3%; and vancomycin, 100%. Two strains with spa t001 displayed ceftaroline MICs of 4mg/L. Three strains with spa types t002, t064 and t437 showed high-level mupirocin resistance (MIC>1024mg/L). In conclusion, there was a diverse genetic population among the MRSA isolates and no predominant genotype was found. This study identified a few strains with high-level ceftaroline resistance, high-level mupirocin resistance and high-risk genotypes.
authors.affiliation: Department of Clinical Microbiology, Karolinska University Hospital, Karolinska Institute, SE-141 86 Stockholm, Sweden.
authors.forename: Hong
authors.initials: H
authors.lastname: Fang
authors.affiliation: Department of Clinical Microbiology, Karolinska University Hospital, Karolinska Institute, SE-141 86 Stockholm, Sweden.
authors.forename: Inga
authors.initials: I
authors.lastname: Fröding
authors.affiliation: Department of Clinical Microbiology, Karolinska University Hospital, Karolinska Institute, SE-141 86 Stockholm, Sweden.
authors.forename: Boisan
authors.initials: B
authors.lastname: Gian
authors.affiliation: Department of Microbiology, Public Health Agency of Sweden, SE-171 82 Solna, Sweden.
authors.forename: Sara
authors.initials: S
authors.lastname: Hæggman
authors.affiliation: Communicable Disease Control, Stockholm County, SE-118 91 Stockholm, Sweden.
authors.forename: Ulla-Britt
authors.initials: UB
authors.lastname: Tollström
authors.affiliation: Department of Clinical Microbiology, Karolinska University Hospital, Karolinska Institute, SE-141 86 Stockholm, Sweden.
authors.forename: Måns
authors.initials: M
authors.lastname: Ullberg
authors.affiliation: Department of Clinical Microbiology, Karolinska University Hospital, Karolinska Institute, SE-141 86 Stockholm, Sweden. Electronic address: Carl.Erik.Nord@ki.se.
authors.forename: Carl Erik
authors.initials: CE
authors.lastname: Nord
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015373:Bacterial Typing Techniques; D002511:Cephalosporins / Q000494:pharmacology; D005838:Genotype; D000069349:Linezolid / Q000494:pharmacology; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D017720:Molecular Epidemiology; D016712:Mupirocin / Q000494:pharmacology; D013203:Staphylococcal Infections / Q000382:microbiology; D013548:Sweden; D014640:Vancomycin / Q000494:pharmacology; D000097583:Ceftaroline
chemical_list: D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D000069349:Linezolid; D016712:Mupirocin; D014640:Vancomycin; D000097583:Ceftaroline
keywords: Ceftaroline; Genotype; Linezolid; MRSA; Mupirocin; Vancomycin