title: Molecular epidemiology of methicillin-resistant Staphylococcus aureus in a burn unit from Brazil.
abstract: Methicillin-resistant Staphylococcus aureus (MRSA) poses a threat for patients in burn units. Studies that mix epidemiological designs with molecular typing may contribute to the development of strategies for MRSA control. We conducted a study including: molecular characterization of Staphylococcal Chromosome Cassette mecA (SCCmec), strain typing with pulsed field gel electrophoresis (PFGE) and detection of virulence genes, altogether with a case-case-control study that assessed risk factors for MRSA and for methicillin-susceptible S. aureus (MSSA), using S. aureus negative patients as controls. Strains were collected from clinical and surveillance cultures from October 2006 through March 2009. MRSA was isolated from 96 patients. Most isolates (94.8%) harbored SCCmec type III. SCCmec type IV was identified in isolates from four patients. In only one case it could be epidemiologically characterized as "community-associated". PFGE typing identified 36 coexisting MRSA clones. When compared to MSSA (38 isolates), MRSA isolates were more likely to harbor two virulence genes: tst and lukPV. Previous stay in other hospital and admission to Intensive Care Unit were independent risk factors for both MRSA and MSSA, while the number of burn wound excisions was significantly related with the former (OR=6.80, 95%CI=3.54-13.07). In conclusion, our study found polyclonal endemicity of MRSA in a burn unit, possibly related to importing of strains from other hospitals. Also, it pointed out to a role of surgical procedures in the dissemination of MRSA strains.
authors.affiliation: Department of Tropical Diseases, Faculdade de Medicina de Botucatu, Unesp - Univ Estadual Paulista (São Paulo State University), Botucatu city, São Paulo State, Brazil.
authors.forename: Marcus Vinicius Pimenta
authors.initials: MV
authors.lastname: Rodrigues
authors.forename: Carlos Magno Castelo Branco
authors.initials: CM
authors.lastname: Fortaleza
authors.forename: Danilo Flávio Moraes
authors.initials: DF
authors.lastname: Riboli
authors.forename: Renata Silveira
authors.initials: RS
authors.lastname: Rocha
authors.forename: Cristiane
authors.initials: C
authors.lastname: Rocha
authors.forename: Maria de Lourdes Ribeiro de Souza
authors.initials: Mde L
authors.lastname: da Cunha
mesh_terms: D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D001938:Brazil / Q000453:epidemiology; D002053:Burn Units / Q000706:statistics & numerical data; D016022:Case-Control Studies; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000235:genetics* / Q000302:isolation & purification; D012189:Retrospective Studies; D012307:Risk Factors; D013203:Staphylococcal Infections / Q000175:diagnosis / Q000188:drug therapy / Q000453:epidemiology*; D037521:Virulence Factors / Q000235:genetics; D055815:Young Adult
chemical_list: D000900:Anti-Bacterial Agents; D037521:Virulence Factors
keywords: MRSA burn units; Molecular epidemiology; Risk factors; Staphylococcus aureus