Genomic Characterization of USA300 Methicillin-Resistant Staphylococcus aureus (MRSA) to Evaluate Intraclass Transmission and Recurrence of Skin and Soft Tissue Infection (SSTI) Among High-Risk Military Trainees.
Eugene V Millar, Gregory K Rice, Emad M Elassal, Carey D Schlett, Jason W Bennett, Cassie L Redden, Deepika Mor, Natasha N Law, David R Tribble, Theron Hamilton, Michael W Ellis, Kimberly A Bishop-Lilly
Author Information
Eugene V Millar: Infectious Disease Clinical Research Program, Department of Preventive Medicine and Biostatistics, Uniformed Services University of the Health Sciences, Bethesda.
Gregory K Rice: Henry M. Jackson Foundation for the Advancement of Military Medicine, Rockville.
Emad M Elassal: Infectious Disease Clinical Research Program, Department of Preventive Medicine and Biostatistics, Uniformed Services University of the Health Sciences, Bethesda.
Carey D Schlett: Infectious Disease Clinical Research Program, Department of Preventive Medicine and Biostatistics, Uniformed Services University of the Health Sciences, Bethesda.
Jason W Bennett: Walter Reed Army Institute of Research, Silver Spring.
Cassie L Redden: Henry M. Jackson Foundation for the Advancement of Military Medicine, Rockville.
Deepika Mor: Infectious Disease Clinical Research Program, Department of Preventive Medicine and Biostatistics, Uniformed Services University of the Health Sciences, Bethesda.
Natasha N Law: Infectious Disease Clinical Research Program, Department of Preventive Medicine and Biostatistics, Uniformed Services University of the Health Sciences, Bethesda.
David R Tribble: Infectious Disease Clinical Research Program, Department of Preventive Medicine and Biostatistics, Uniformed Services University of the Health Sciences, Bethesda.
Theron Hamilton: Naval Medical Research Center, Biological Defense Research Directorate, Fort Detrick.
Michael W Ellis: University of Toledo College of Medicine and Life Sciences, Ohio.
Kimberly A Bishop-Lilly: Henry M. Jackson Foundation for the Advancement of Military Medicine, Rockville.
BACKGROUND: Military trainees are at increased risk for methicillin-resistant Staphylococcus aureus (MRSA) Skin and Soft Tissue infection (SSTI). Whole genome sequencing (WGS) can refine our understanding of MRSA transmission and microevolution in congregate settings. METHODS: We conducted a prospective case-control study of SSTI among US Army infantry trainees at Fort Benning, Georgia, from July 2012 to December 2014. We identified clusters of USA300MRSASSTI within select training classes and performed WGS on clinical isolates. We then linked genomic, phylogenetic, epidemiologic, and clinical data in order to evaluate intra- and interclass disease transmission. Furthermore, among cases of recurrent MRSASSTI, we evaluated the intrahost relatedness of infecting strains. RESULTS: Nine training classes with ≥5 cases of USA300MRSASSTI were selected. Eighty USA300MRSA clinical isolates from 74 trainees, 6 (8.1%) of whom had recurrent infection, were subjected to WGS. We identified 2719 single nucleotide variants (SNVs). The overall median (range) SNV difference between isolates was 173 (1-339). Intraclass median SNV differences ranged from 23 to 245. Two phylogenetic clusters were suggestive of interclass MRSA transmission. One of these clusters stemmed from 2 classes that were separated by a 13-month period but housed in the same barracks. Among trainees with recurrent MRSASSTI, the intrahost median SNV difference was 7.5 (1-48). CONCLUSIONS: Application of WGS revealed intra- and interclass transmission of MRSA among military trainees. An interclass cluster between 2 noncontemporaneous classes suggests a long-term reservoir for MRSA in this setting.
