title: Study on biofilm-forming properties of clinical isolates of Staphylococcus aureus.
abstract: BACKGROUND
  The purpose of this study was to observe the formation of biofilm, an important virulence factor, by isolates of Staphylococcus aureus (S. aureus) in Pakistan by different conventional methods and through electron microscopy.
  
  
  METHODS
  We screened 115 strains of S. aureus isolated from different clinical specimens by tube method (TM), air-liquid interface coverslip assay method, Congo red agar (CRA) method, and scanning electron microscopy (SEM).
  
  
  RESULTS
  Out of 115 S. aureus isolates, 63 (54.78%) showed biofilm formation by tube method. Biofilm forming bacteria were further categorized as high producers (n = 23, 20%) and moderate producers (n = 40, 34.78%). TM coordinated well with the coverslip assay for strong biofilm-producing strains in 19 (16.5%) isolates. By coverslip method, weak producers were difficult to differentiate from biofilm negative isolates. Screening on CRA showed biofilm formation only in four (3.47%) strains. Scanning electron micrographs showed the biofilm-forming strains of S. aureus arranged in a matrix on the propylene surface and correlated well with the TM.
  
  
  CONCLUSIONS
  Biofilm production is a marker of virulence for clinically relevant staphylococcal infections. It can be studied by various methods but screening on CRA is not recommended for investigation of biofilm formation in Staphylococcus aureus. Electron micrograph images correlate well with the biofilm production as observed by TM.
authors.affiliation: Dow Medical College Karachi, Karachi, Pakistan. y.taj@hotmail.com
authors.forename: Yasmeen
authors.initials: Y
authors.lastname: Taj
authors.forename: Farhan
authors.initials: F
authors.lastname: Essa
authors.forename: Faisal
authors.initials: F
authors.lastname: Aziz
authors.forename: Shahana Urooj
authors.initials: SU
authors.lastname: Kazmi
mesh_terms: D001431:Bacteriological Techniques; D018441:Biofilms / Q000254:growth & development*; D006801:Humans; D008854:Microscopy, Electron; D010154:Pakistan; D013203:Staphylococcal Infections / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000302:isolation & purification* / Q000472:pathogenicity / Q000502:physiology*; D014774:Virulence