Colonial architecture and growth dynamics of Staphylococcus aureus resistant to methicillin.
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.
Gómez-Aguado
Fernando
F
Departamento de Anatomía Patológica, Hospital Carlos III de Madrid, Universidad Complutense de Madrid, Spain.
Gómez-Lus
Maria Luisa
ML
Corcuera
María Teresa
MT
Alou
Luis
L
Alonso
María José
MJ
Sevillano
David
D
Val
Daniel
D
Palmeiro
Alejandra
A
Iglesias
Nuria
N
Prieto
José
J
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D003470:Culture Media; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects* / Q000254:growth & development*
D000900:Anti-Bacterial Agents; D003470:Culture Media