title: Association of Biofilm Formation, Psl Exopolysaccharide Expression, and Clinical Outcomes in Pseudomonas aeruginosa Keratitis: Analysis of Isolates in the Steroids for Corneal Ulcers Trial.
abstract: OBJECTIVE
  Bacterial virulence factors are increasingly recognized as important in the understanding of clinical infections.
  
  
  OBJECTIVE
  To determine whether 2 potential virulence factors, in vitro biofilm formation and Psl exopolysaccharide (EPS) expression, influence clinical presentation or outcomes in Pseudomonas aeruginosa keratitis.
  
  
  METHODS
  Laboratory investigation using P aeruginosa clinical isolates from the double-blind Steroids for Corneal Ulcers Trial (SCUT), which included patients at Aravind Eye Hospital, Proctor Foundation, University of California, San Francisco, and Dartmouth-Hitchcock Medical Center. SCUT was conducted from September 1, 2006, through February 22, 2010. All data used in this study were obtained during this period. Pseudomonas aeruginosa clinical isolates from SCUT were evaluated for in vitro biofilm formation, and Psl EPS expression was assessed using an anti-Psl monoclonal antibody (mAb) enzyme-linked immunosorbent assay. Planktonic growth kinetics and the susceptibility to anti-Psl mAb-mediated opsonophagocytic killing (OPK) were also evaluated in a subset of isolates. Linear regression assessed associations between SCUT patients' visual acuity and their corresponding biofilm formation and Psl EPS expression. Generalized estimating equation regression models were used to assess whether the change in visual acuity among SCUT patients was associated with Psl EPS expression or biofilm formation.
  
  
  METHODS
  Biofilm formation, Psl production, OPK, and visual acuity.
  
  
  RESULTS
  The P aeruginosa SCUT strains produced a mean (SD) in vitro biofilm score of 1.06 (0.32) (range 0.17-2.12). A 1-unit increase in biofilm was associated with a worse visual acuity of 2 lines measured in SCUT patients at baseline (0.20 logMAR; 95% CI, -0.03 to 0.44; P = .09) and 3 months (0.21 logMAR; 95% CI, 0.003 to 0.44; P = .047). Of 101 confirmed P aeruginosa SCUT isolates, 100 expressed Psl EPSs. In addition, all Psl-positive strains evaluated in the OPK assay were susceptible to anti-Psl mAb-mediated OPK.
  
  
  CONCLUSIONS
  The ability of P aeruginosa keratitis isolates to form biofilms in vitro was correlated with worse vision at presentation and after 3 months in SCUT. Ninety-nine percent of P aeruginosa keratitis isolates from SCUT produced Psl EPSs, and 100% of these evaluated Psl-positive isolates were susceptible to anti-Psl mAb-mediated OPK. These data indicate that biofilm formation and Psl EPSs may be candidate targets for novel therapeutics against P aeruginosa keratitis.
authors: Deparments of Surgery (Ophthalmology) and Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire.
authors: Michael E
authors: ME
authors: Zegans
authors: MedImmune LLC, Gaithersburg, Maryland.
authors: Antonio
authors: A
authors: DiGiandomenico
authors: F. I. Proctor Foundation and Department of Ophthalmology, University of California, San Francisco.
authors: Kathryn
authors: K
authors: Ray
authors: Deparments of Surgery (Ophthalmology) and Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire.
authors: Amanda
authors: A
authors: Naimie
authors: MedImmune LLC, Gaithersburg, Maryland.
authors: Ashley E
authors: AE
authors: Keller
authors: MedImmune LLC, Gaithersburg, Maryland.
authors: C Kendall
authors: CK
authors: Stover
authors: Aravind Eye Hospital, Tamil Nadu, India.
authors: Prajna
authors: P
authors: Lalitha
authors: Aravind Eye Hospital, Tamil Nadu, India.
authors: Muthiah
authors: M
authors: Srinivasan
authors: F. I. Proctor Foundation and Department of Ophthalmology, University of California, San Francisco.
authors: Nisha R
authors: NR
authors: Acharya
authors: F. I. Proctor Foundation and Department of Ophthalmology, University of California, San Francisco.
authors: Thomas M
authors: TM
authors: Lietman
mesh_terms: D000305:Adrenal Cortex Hormones / Q000008:administration & dosage / Q000494:pharmacology*; D000328:Adult; D018441:Biofilms / Q000187:drug effects*; D015415:Biomarkers / Q000378:metabolism; D003320:Corneal Ulcer / Q000188:drug therapy / Q000382:microbiology; D004311:Double-Blind Method; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007634:Keratitis / Q000188:drug therapy / Q000382:microbiology*; D008297:Male; D008875:Middle Aged; D011134:Polysaccharides / Q000378:metabolism*; D011552:Pseudomonas Infections / Q000175:diagnosis / Q000188:drug therapy*; D011550:Pseudomonas aeruginosa / Q000302:isolation & purification / Q000502:physiology*; D013997:Time Factors; D016896:Treatment Outcome; D014792:Visual Acuity
chemical_list: D000305:Adrenal Cortex Hormones; D015415:Biomarkers; D011134:Polysaccharides