title: Antibiosis interaction of Staphylococccus aureus on Aspergillus fumigatus assessed in vitro by mixed biofilm formation.
abstract: BACKGROUND
  Microorganisms of different species interact in several ecological niches, even causing infection. During the infectious process, a biofilm of single or multispecies can develop. Aspergillus fumigatus and Staphyloccocus aureus are etiologic agents that can cause infectious keratitis. We analyzed in vitro single A. fumigatus and S. aureus, and mixed A. fumigatus-S. aureus biofilms. Both isolates were from patients with infectious keratitis. Structure of the biofilms was analyzed through microscopic techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), confocal, and fluorescence microscopy (CLSM) in mixed biofilm as compared with the single A. fumigatus biofilm.
  
  
  RESULTS
  To our knowledge, this is the first time that the structural characteristics of the mixed biofilm A. fumigatus-A. fumigatus were described and shown. S. aureus sharply inhibited the development of biofilm formed by A. fumigatus, regardless of the stage of biofilm formation and bacterial inoculum. Antibiosis effect of bacterium on fungus was as follows: scarce production of A. fumigatus biofilm; disorganized fungal structures; abortive hyphae; and limited hyphal growth; while conidia also were scarce, have modifications in their surface and presented lyses. Antagonist effect did not depend on bacterial concentration, which could probably be due to cell-cell contact interactions and release of bacterial products. In addition, we present images about the co-localization of polysaccharides (glucans, mannans, and chitin), and DNA that form the extracellular matrix (ECM). In contrast, single biofilms showed extremely organized structures: A. fumigatus showed abundant hyphal growth, hyphal anastomosis, and channels, as well as some conidia, and ECM. S. aureus showed microcolonies and cell-to-cell bridges and ECM.
  
  
  CONCLUSIONS
  Herein we described the antibiosis relationship of S. aureus against A. fumigatus during in vitro biofilm formation, and report the composition of the ECM formed.
authors.affiliation: Laboratorio de Micología Médica, Depto. de Microbiología, Escuela Nacional de Ciencias Biológicas (ENCB), Instituto Politécnico Nacional (IPN). Carpio y Plan de Ayala s/n, Col. Casco de Santo Tomás, Del. Miguel Hidalgo, 11340, Mexico City, Mexico. schielle777@hotmail.com.
authors.forename: Adrián
authors.initials: A
authors.lastname: Ramírez Granillo
authors.affiliation: Laboratorio de Micología Médica, Depto. de Microbiología, Escuela Nacional de Ciencias Biológicas (ENCB), Instituto Politécnico Nacional (IPN). Carpio y Plan de Ayala s/n, Col. Casco de Santo Tomás, Del. Miguel Hidalgo, 11340, Mexico City, Mexico. magameca@yahoo.com.mx.
authors.forename: María Gabriela Medina
authors.initials: MG
authors.lastname: Canales
authors.affiliation: Unidad de Microscopía ENCB, IPN, 11340, Mexico City, Mexico. sanzespindola@gmail.com.
authors.forename: María Esther Sánchez
authors.initials: ME
authors.lastname: Espíndola
authors.affiliation: Laboratorio de Micología Médica, Depto. de Microbiología, Escuela Nacional de Ciencias Biológicas (ENCB), Instituto Politécnico Nacional (IPN). Carpio y Plan de Ayala s/n, Col. Casco de Santo Tomás, Del. Miguel Hidalgo, 11340, Mexico City, Mexico. angeles.12mar@hotmail.com.
authors.forename: María Angeles
authors.initials: MA
authors.lastname: Martínez Rivera
authors.affiliation: Microbiology and Ocular Proteomics, Research Unit, Institute of Ophthalmology "Fundación de Asistencia Privada Conde de Valenciana". Chimalpopoca 14, Col. Obrera, Del. Cuauhtémoc, 06800, Mexico City, Mexico. vmanuelbl@gmail.com.
authors.forename: Victor Manuel Bautista
authors.initials: VM
authors.lastname: de Lucio
authors.affiliation: Laboratorio de Micología Médica, Depto. de Microbiología, Escuela Nacional de Ciencias Biológicas (ENCB), Instituto Politécnico Nacional (IPN). Carpio y Plan de Ayala s/n, Col. Casco de Santo Tomás, Del. Miguel Hidalgo, 11340, Mexico City, Mexico. avrodriguez@hotmail.com.
authors.forename: Aída Verónica Rodríguez
authors.initials: AV
authors.lastname: Tovar
mesh_terms: D000898:Antibiosis / Q000502:physiology*; D001232:Aspergillus fumigatus / Q000254:growth & development / Q000302:isolation & purification / Q000648:ultrastructure*; D018441:Biofilms / Q000254:growth & development*; D015169:Colony Count, Microbial; D003315:Cornea / Q000382:microbiology; D005109:Extracellular Matrix / Q000648:ultrastructure; D062610:Fungal Polysaccharides / Q000737:chemistry; D006801:Humans; D025301:Hyphae / Q000254:growth & development / Q000648:ultrastructure; D007634:Keratitis / Q000382:microbiology / Q000473:pathology; D008855:Microscopy, Electron, Scanning; D011135:Polysaccharides, Bacterial / Q000737:chemistry; D013172:Spores, Fungal / Q000254:growth & development / Q000648:ultrastructure; D013211:Staphylococcus aureus / Q000254:growth & development / Q000302:isolation & purification / Q000472:pathogenicity* / Q000648:ultrastructure*
chemical_list: D062610:Fungal Polysaccharides; D011135:Polysaccharides, Bacterial