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2020 OMIG Abstract

Characterization of Staphylococcus aureus Corneal Keratitis Isolates:
A Whole Genome Perspective

William Johnson PhD1, Michael Sohn PhD2, Samantha Taffner3, Payel Chatterjee PhD1,
Nicole Pecora MD, PhD3, Rachel Wozniak MD, PhD1

1Department of Ophthalmology, University of Rochester Medical Center; 2Department of Biostatistics and Computational Biology, University of Rochester Medical Center; 3Department of Pathology and Laboratory Medicine, University of Rochester Medical Center, Rochester, NY

Purpose: Utilize whole-genome sequencing (WGS) to characterize S. aureus ocular isolates with respect to multi-locus sequence typing (MLST) and virulence factors in order to provide insight into the epidemiology and pathogenesis of this important ocular pathogen.

Methods: 163 S. aureus ocular isolates from diverse geographic locations between 2008-2017 underwent whole genome sequencing using Illumina next generation technology. A custom in silico pipeline designed for automated high-throughput genomic analysis was developed for MLST and the identification of 240 unique virulence factors. Cluster analysis was used to group S. aureus ocular isolates based on the presence/absence of virulence factors. Beta diversity was measured by the Jaccard distance and assessed using permutational multivariate analysis of variance, and Fisher’s exact test or chi-square test was used to analyze categorical variables.

Results: We identified 44 MLST types with ST5 (21%), ST8 (15%) and ST30 (11%) most commonly identified. Among MRSA isolates, 13 STs were identified with ST5 (39%) and ST8 (27%) the most common, while MSSA isolates demonstrated wider diversity with ST30 (13%) and ST5 (12%) the most common among 37 unique STs. The optimum number of clusters based on the gap-statistic via bootstrap resampling was four, and these clusters were significantly associated with MRSA/MSSA (p=1.08x10-6). They were also significantly associated with geographic location (p=0.003). However, clusters were not associated with sex or age. Significant differences of beta diversity measures between MRSA and MSSA were evident
(p < 0.0001). Moreover, significant differences in the distribution of several bacterial adherence factors, capsular polysaccharide components, superantigens and toxins were identified.

Conclusion: WGS is a powerful tool to study human pathogens. The distribution of strain types as well as virulence factors can provide insight into keratitis pathogenesis as well as provide markers for disease transmission.

Disclosure: N

Support: Research to Prevent Blindness Career Development Award (R Wozniak)



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