Background. Whole-genome sequencing (WGS) has typically been used to confirm or refute hospital/ward outbreaks of methicillin-resistant Staphylococcus aureus (MRSA) identified through routine practice. However, appropriately targeted WGS strategies that identify routinely "undetectable" transmission remain the ultimate aim. Methods. WGS of MRSA isolates sent to a regional microbiological laboratory was performed as part of a 12-month prospective observational study. Phylogenetic analyses identified a genetically related cluster of E-MRSA15 isolated from patients registered to the same general practice (GP) surgery. This led to an investigation to identify epidemiological links, find additional cases, and determine potential for ongoing transmission. Results. We identified 15 MRSA-positive individuals with 27 highly related MRSA isolates who were linked to the GP surgery, 2 of whom died with MRSA bacteremia. Of the 13 cases that were further investigated, 11 had attended a leg ulcer/podiatry clinic. Cases lacked epidemiological links to hospitals, suggesting that transmission occurred elsewhere. Environmental and staff screening at the GP surgery did not identify an ongoing source of infection. Conclusions. Surveillance in the United Kingdom shows that the proportion of MRSA bacteremias apportioned to hospitals is decreasing, suggesting the need for greater focus on the detection of MRSA outbreaks and transmission in the community. This case study confirms that the typically nosocomial lineage (E-MRSA15) can transmit within community settings. Our study exemplifies the continued importance of WGS in detecting outbreaks, including those which may be missed by routine practice, and suggests that universal WGS of bacteremia isolates may help detect outbreaks in low-surveillance settings.
Bibliographical noteFunding Information:
Disclaimer. The study sponsors had no role in study design, data collection, data analysis, data interpretation, or writing of the report. The public health investigation was supported by Public Health England.
Financial support. This work was supported by grants from the UK Clinical Research Collaboration Translational Infection Research Initiative and the Medical Research Council (grant number G1000803), with contributions to the grant from the Biotechnology and Biological Sciences Research Council, the National Institute for Health Research on behalf of the Department of Health, and the Chief Scientist Office of the Scottish Government Health Directorate (to S. J. P.); by a Healthcare Infection Society Major Research Grant (to S. J. P.); and by Wellcome Trust grant number 098051 awarded to the Wellcome Trust Sanger Institute. M. S. T. was a Wellcome Trust Clinical PhD Fellow. F. C. was supported by the Wellcome Trust (grant number 201344/Z/16/Z). Potential conflicts of interest. N. M. B. is on the advisory board for Discuva Ltd. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.
© 2017 The Author. Published by Oxford University Press for the Infectious Diseases Society of America.
- general practice
- genome sequencing