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Infect Control Hosp Epidemiol. 2018 Oct 4:1-7. doi: 10.1017/ice.2018.239. [Epub ahead of print]

Whole-genome sequencing for methicillin-resistant Staphylococcus aureus (MRSA) outbreak investigation in a neonatal intensive care unit.

Author information

1
1Division of Pediatric Infectious Diseases,Department of Pediatric and Adolescent Medicine,Mayo Clinic,Rochester,Minnesota.
2
2Division of Clinical Microbiology,Department of Laboratory Medicine and Pathology,Mayo Clinic Rochester,Minnesota.
3
4Infection Prevention and Control,Mayo Clinic,Rochester,Minnesota.
4
3Division of Infectious Diseases,Department of Medicine,Mayo Clinic,Rochester,Minnesota.
5
5Division of Neonatal Medicine,Department of Pediatric and Adolescent Medicine,Mayo Clinic,Rochester,Minnesota.
6
7Department of Surgery,Mayo Clinic,Rochester,Minnesota.

Abstract

OBJECTIVE:

To evaluate whole-genome sequencing (WGS) as a molecular typing tool for MRSA outbreak investigation.

DESIGN:

Investigation of MRSA colonization/infection in a neonatal intensive care unit (NICU) over 3 years (2014-2017).

SETTING:

Single-center level IV NICU.PatientsNICU infants and healthcare workers (HCWs).

METHODS:

Infants were screened for MRSA using a swab of the anterior nares, axilla, and groin, initially by targeted (ring) screening, and later by universal weekly screening. Clinical cultures were collected as indicated. HCWs were screened once using swabs of the anterior nares. MRSA isolates were typed using WGS with core-genome multilocus sequence typing (cgMLST) analysis and by pulsed-field gel electrophoresis (PFGE). Colonized and infected infants and HCWs were decolonized. Control strategies included reinforcement of hand hygiene, use of contact precautions, cohorting, enhanced environmental cleaning, and remodeling of the NICU.

RESULTS:

We identified 64 MRSA-positive infants: 53 (83%) by screening and 11 (17%) by clinical cultures. Of 85 screened HCWs, 5 (6%) were MRSA positive. WGS of MRSA isolates identified 2 large clusters (WGS groups 1 and 2), 1 small cluster (WGS group 3), and 8 unrelated isolates. PFGE failed to distinguish WGS group 2 and 3 isolates. WGS groups 1 and 2 were codistributed over time. HCW MRSA isolates were primarily in WGS group 1. New infant MRSA cases declined after implementation of the control interventions.

CONCLUSION:

We identified 2 contemporaneous MRSA outbreaks alongside sporadic cases in a NICU. WGS was used to determine strain relatedness at a higher resolution than PFGE and was useful in guiding efforts to control MRSA transmission.

PMID:
30282566
DOI:
10.1017/ice.2018.239

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