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2015 OMIG Abstract 8

Staphylococcus aureus Keratitis: Multi-Locus Sequence Typing and Genome Sequencing to Identify Lineage, Virulence and Antibiotic Resistance Genes
Irmgard Behlau1,2, Jacqueline N. Martin1,2, David Lazinski1, Susan R. Heimer2, Kelli Palmer
Elizabeth M. Leonard
2, Andrew Wright1, Michael S. Gilmore2, Claes H. Dohlman2, and Andrew Camilli1
1Molecular Biology & Microbiology and Ophthalmology, Tufts - Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, MA
2Ophthalmology, Massachusetts Eye and Ear Infirmary/Schepens Eye Research Institute, Harvard Medical School, Boston, MA
3Molecular & Cell Biology, Univ. of Texas-Dallas, Dallas, TX

Purpose: S. aureus is an opportunistic pathogen.  It resides as a normal commensal of the human skin and nasopharynx, yet S. aureus infection appears to be predominantly caused by only a subset of the organisms. Sequence-based methods allow us to track epidemiological lineages.  Whole genome sequencing enables us to identify new virulence and/or antibiotic resistance genes associated with keratitis.
Methods: S. aureus clinical isolates were prospectively collected from the Boston area.  The diagnosis of clinical keratitis and associated risk factors was by medical record review. Keratitis-associated S. aureus strains were assessed for: 1) antibiotic susceptibility by CSLI standards, 2) biofilm robustness by gentian violet staining, 3) genetic lineage, and 4) whole genome sequencing was performed using Illumina sequencing technology.
Results: Risk factors included trauma, prior surgery, soft contact lens wear, and the presence of a surgical implant or environmental foreign body; 25% had no identifiable risk factor.  Prior antibiotic usage did correlate strongly with methicillin-resistance. More than one-third of all the S. aureus keratitis-associated isolates were caused by a single clone, ST5, with both methicillin-sensitive and -resistant S. aureus strains represented. Using a patented linker and paired-end library construction, whole genome sequencing was performed inexpensively and provided insight into virulence and antibiotic resistance genes.
Conclusions: These results suggest that there may be specific S. aureus lineages that possess genotypic characteristics that enable S. aureus to more effectively cause sight-threatening keratitis and other surface-associated (biofilm) infections.  Additionally, new genome sequencing technology can give us insight into novel virulence traits that may be uniquely associated with different ocular and biofilm infections.  Further work will explore the feasibility of cost-effective, real-time genomic sequencing technology into clinical application for hospital microbiology laboratories.

2015 Agenda and Abstracts | < Previous | Next >