942. Continuous surveillance by whole genome sequencing to identify and manage MRSA outbreaks
Session: Oral Abstract Session: HAI: Surveillance and Reporting
Friday, October 28, 2016: 10:30 AM
Room: 388-390
Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a common and clinically significant pathogen associated with high mortality. Although epidemiologic analyses by infection control agencies are routinely undertaken, the full genetic basis of this pathogen is not routinely monitored or defined with precision greater than multilocus sequence typing (MLST) results, complicating the detection and management of outbreaks of this highly clonal pathogen. We implemented a whole-genome sequencing surveillance program to map the genetic diversity of all MRSA bacteremias identified in an urban hospital center over the course of one year and used it to manage a large outbreak during this time.

Methods: Pacbio long-read sequencing was used to assemble high-quality complete genomes for 137 MRSA isolates. Phylogenetic analyses were performed using Mugsy, Gblocks and RAxML to determine relatedness of bacterial strains and identify transmission events, which were correlated with epidemiological temporal-spatial analyses. Additionally, genomes were compared with NUCmer to characterise the evolutionary changes that occurred in endemic strains.

Results: WGS revealed a diverse MRSA population that included 36% ST105, 36% ST8, 16% ST5, and 12% other sequence types. Isolates within each ST were genetically distinct by WGS indicating that direct transmissions were generally rare; however in one case we confirmed a large outbreak of a subpopulation of MRSA ST105 in a neonatal intensive care unit. Related cases were identified in other wards, including a case that pre-dated the epidemiologically determined outbreak cluster by one month.

Conclusion: We demonstrate that continuous surveillance of WGS is both feasible and necessary to identify transmissions of MRSA with high accuracy and precision, and to map the full extent of outbreaks. Notably, near-real time sequencing of MRSA isolates permits early detection of transmission events compared to standard epidemiological methods, enabling immediate infection control interventions to pre-emptively manage outbreaks.

Mitchell Sullivan, PhD1, Deena Altman, MD2, Elizabeth Webster, BS1, Martha Lewis, BS1, Zenab Khan, n/a1, Colleen Beckford, MS1, Brianne Ciferri, MPH1, Gintaras Deikus, PhD1, Angela Rendo, BS3, Flora Samaroo, BS3, Robert Sebra, Ph.D.1, Fran Wallach, MD2, Gopi Patel, MD2, Camille Hamula, PhD3, Ali Bashir, PhD1, Eric Schadt, PhD1, Andrew Kasarskis, PhD1, Kathleen Gibbs, MD4 and Harm Van Bakel, PhD1, (1)Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, (2)Infectious Diseases, Icahn School of Medicine at Mount Sinai, New York, NY, (3)Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, (4)Pediatrics, Mount Sinai Hospital, New York, NY

Disclosures:

M. Sullivan, None

D. Altman, None

E. Webster, None

M. Lewis, None

Z. Khan, None

C. Beckford, None

B. Ciferri, None

G. Deikus, None

A. Rendo, None

F. Samaroo, None

R. Sebra, None

F. Wallach, None

G. Patel, None

C. Hamula, None

A. Bashir, None

E. Schadt, None

A. Kasarskis, None

K. Gibbs, None

H. Van Bakel, None

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