title: Colonial architecture and growth dynamics of Staphylococcus aureus resistant to methicillin.
abstract: The aim of the study was to explore the structure and growth dynamics of Staphylococcus aureus resistant to methicillin (MRSA) colonies using semithin sections visualized by light microscope. One S. aureus susceptible to methicillin (MSSA) and one MRSA clinical strains were studied. Colonies in agar plates were embedded in epoxy resin after each incubation period (24 h and 48 h) at 37 degrees . Semithin sections of 0.5 µm were stained with toluidine blue and visualized by light microscope. Microscopically, no structural differences were observed between SASM and SARM colonies but differences were observed in both strains between 24 and 48 h incubation periods. Colonies showed two layers clearly differentiated at 24 h independently of the resistance to methicillin: (A) one basal layer with high density of population in contact with culture media, and (B) one superficial layer with a lower density of population. Colonies showed four layers at 48 h: (A) one basal layer with high density of population; (B) one clear layer constituted by very degraded bacterial remains in which can be observed cocci dispersed with their dyeing properties; (C) one mixed layer constituted by viable bacteria and little degraded bacterial remains (D) one superficial layer with a lower density of population than basal layer. Colonial architecture is a complex and time-dependent process.
authors.affiliation: Departamento de Anatomía Patológica, Hospital Carlos III de Madrid, Universidad Complutense de Madrid, Spain.
authors.forename: Fernando
authors.initials: F
authors.lastname: Gómez-Aguado
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Gómez-Lus
authors.forename: María Teresa
authors.initials: MT
authors.lastname: Corcuera
authors.forename: Luis
authors.initials: L
authors.lastname: Alou
authors.forename: María José
authors.initials: MJ
authors.lastname: Alonso
authors.forename: David
authors.initials: D
authors.lastname: Sevillano
authors.forename: Daniel
authors.initials: D
authors.lastname: Val
authors.forename: Alejandra
authors.initials: A
authors.lastname: Palmeiro
authors.forename: Nuria
authors.initials: N
authors.lastname: Iglesias
authors.forename: José
authors.initials: J
authors.lastname: Prieto
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D003470:Culture Media; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects* / Q000254:growth & development*
chemical_list: D000900:Anti-Bacterial Agents; D003470:Culture Media