title: Clonal and antibiotic resistance profiles of methicillin-resistant Staphylococcus aureus (MRSA) from a Portuguese hospital over time.
abstract: Methicillin-resistant Staphylococcus aureus (MRSA) isolates recovered from a general hospital in Oporto, Portugal, during two periods (1992-1993 and 1996-2000) were characterized by pulsed-field gel electrophoresis (PFGE) of SmaI fragments, and by hybridization of ClaI digests with mecA and Tn554 probes, discriminating the isolates in mecA::Tn554::PFGE genotypes. In addition, a representative sample of the defined genotypes was characterized by multilocus sequence typing (MLST) and SCCmec (staphylococcal cassette chromosome mec) typing, generating the corresponding ST-SCCmec types. In 1992-1993, 77% of MRSA belonged to the Iberian clone (genotype I::E::A or ST247-IA). In 1996-2000, the frequency of this clone decreased to 19% and the majority (69%) of the isolates belonged to another international clone, the Brazilian MRSA (genotype XI::B::B or ST239-IIIA). Trimethoprim/sulfamethoxazole (SXT) was confirmed to be an important phenotypic marker to distinguish the Iberian (SXT-susceptible) and the Brazilian (SXT-resistant) clones in MRSA isolates from Portugal. Our observations document major shifts in the dominant MRSA clonal types that occurred in this hospital since 1992, suggesting a selective advantage of the Brazilian relatively to the Iberian clone. In addition to these two MRSA clones that are the most frequent in Portuguese hospitals since the early 1990s, sporadic MRSA clones (representing 14% of the total) were identified and characterized.
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: M
authors.initials: M
authors.lastname: Aires de Sousa
authors.forename: I Santos
authors.initials: IS
authors.lastname: Sanches
authors.forename: R
authors.initials: R
authors.lastname: Sá-Leão
authors.forename: J M
authors.initials: JM
authors.lastname: Cabeda
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; D003428:Cross Infection / Q000453:epidemiology / Q000382:microbiology*; D004351:Drug Resistance; D016521:Electrophoresis, Gel, Pulsed-Field; D005838:Genotype; D006801:Humans; D017403:In Situ Hybridization; D016106:Methicillin Resistance; D010641:Phenotype; D011174:Portugal / Q000453:epidemiology; D013203:Staphylococcal Infections / Q000453:epidemiology / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000187:drug effects*; D013997:Time Factors; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D015662:Trimethoprim, Sulfamethoxazole Drug Combination