title: Changes in the clonal nature and antibiotic resistance profiles of methicillin-resistant Staphylococcus aureus isolates associated with spread of the EMRSA-15 clone in a tertiary care Portuguese hospital.
abstract: Two hundred eighty methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates recovered from a tertiary care hospital in Oporto, Portugal, between 2003 and 2005 were studied by a combination of molecular typing techniques in order to investigate the genetic backgrounds associated with the changes in the resistance phenotypes observed since 2001 and compare them to those previously found in the hospital. All MRSA isolates were grouped into resistance profiles for a panel of seven antibiotics and characterized by pulsed-field gel electrophoresis (PFGE) and SCCmec (staphylococcal cassette chromosome mec) typing. Representative isolates of PFGE types were further studied by spa typing and multilocus sequence typing. Our findings clearly document that the increasing isolation of nonmultiresistant MRSA strains was associated with the decline (from 69% in 1996 to 2000 to 12% in 2003 to 2005) and massive replacement of the multiresistant Brazilian clone (ST239-IIIA) by the epidemic EMRSA-15 clone (ST22-IV), in which resistance to antibiotics other than beta-lactams is very rare, as the major clone (80% of isolates). The Iberian clone (ST247-IA), a major clone in 1992 to 1993, was represented in the present study by just one isolate. Two other pandemic MRSA clones were detected, as sporadic isolates, for the first time in our hospital: the New York/Japan (ST5-II) and the EMRSA-16 (ST36-II) clones. Furthermore, the pattern of susceptibility of MRSA isolates both to gentamicin and to trimethoprim-sulfamethoxazole was shown to be an excellent phenotypic marker for the discrimination of the EMRSA-15 clone from other nonmultiresistant MRSA clones present in our hospital.
authors.affiliation: Laboratório de Genética Molecular, Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa (ITQB/UNL), Oeiras, Portugal.
authors.forename: M L
authors.initials: ML
authors.lastname: Amorim
authors.forename: N A
authors.initials: NA
authors.lastname: Faria
authors.forename: D C
authors.initials: DC
authors.lastname: Oliveira
authors.forename: C
authors.initials: C
authors.lastname: Vasconcelos
authors.forename: J C
authors.initials: JC
authors.lastname: Cabeda
authors.forename: A C
authors.initials: AC
authors.lastname: Mendes
authors.forename: E
authors.initials: E
authors.lastname: Calado
authors.forename: A P
authors.initials: AP
authors.lastname: Castro
authors.forename: M H
authors.initials: MH
authors.lastname: Ramos
authors.forename: J M
authors.initials: JM
authors.lastname: Amorim
authors.forename: H
authors.initials: H
authors.lastname: de Lencastre
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015373:Bacterial Typing Techniques; D002999:Clone Cells; D003428:Cross Infection / Q000453:epidemiology / Q000382:microbiology; D004269:DNA, Bacterial / Q000235:genetics; D004351:Drug Resistance; D016521:Electrophoresis, Gel, Pulsed-Field; D005838:Genotype; D006761:Hospitals; D006801:Humans; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests; D017720:Molecular Epidemiology; D011174:Portugal / Q000453:epidemiology; D017422:Sequence Analysis, DNA; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000382:microbiology*; D013205:Staphylococcal Protein A / Q000235:genetics; D013211:Staphylococcus aureus / Q000145:classification* / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D013205:Staphylococcal Protein A