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Front. Microbiol. | doi: 10.3389/fmicb.2018.02664

Conjugative Transfer of a Novel Staphylococcal Plasmid Encoding the Biocide Resistance Gene, qacA

Patrick T. LaBreck1,  Gregory K. Rice2, 3,  Adrian C. Paskey1, 2, Emad M. Elassal4, 5,  Regina Z. Cer2, 3, Natasha N. Law4, 6, 7, Carey D. Schlett4, 6,  Jason W. Bennett8, 9, Eugene V. Millar4, 6, Michael W. Ellis10,  Theron Hamilton2, Kimberly A. Bishop-Lilly2 and  D Scott Merrell1*
  • 1Department of Microbiology and Immunology, Uniformed Services University, United States
  • 2Biological Defense Research Directorate, Naval Medical Research Center, United States
  • 3Leidos (United States), United States
  • 4Henry M. Jackson Foundation, United States
  • 5Infectious Diseases Clinical Research Program, Department of Preventive Medicine and Biostatistics, Uniformed Services University of the Health Sciences, United States
  • 6Department of Preventive Medicine and Biostatistics, Uniformed Services University of the Health Sciences, United States
  • 7Martin Army Community Hospital, United States
  • 8Walter Reed Army Institute of Research, United States
  • 9F. Edward Hebert School of Medicine, Uniformed Services University, United States
  • 10College of Medicine and Life Sciences, University of Toledo, United States

Staphylococcus aureus is the leading cause of skin and soft tissue infections (SSTI). Some S. aureus strains harbor plasmids that carry genes that affect resistance to biocides. Among these genes, qacA encodes the QacA Multidrug Efflux Pump that imparts decreased susceptibility to chlorhexidine, a biocide used ubiquitously in healthcare facilities. Furthermore, chlorhexidine has been considered as a S. aureus decolonization strategy in community settings. We previously conducted a chlorhexidine-based SSTI prevention trial among Ft. Benning Army trainees. Analysis of a clinical isolate (C02) from that trial identified a novel qacA-positive plasmid, pC02. Prior characterization of qacA-containing plasmids is limited and conjugative transfer of those plasmids has not been demonstrated. Given the implications of increased biocide resistance, herein we characterized pC02. In silico analysis identified genes typically associated with conjugative plasmids. Moreover, pC02 was efficiently transferred to numerous S. aureus strains and to Staphylococcus epidermidis. We screened additional qacA-positive S. aureus clinical isolates and pC02 was present in 27% of those strains; other unique qacA-harboring plasmids were also identified. Ten strains were subjected to whole genome sequencing. Sequence analysis combined with plasmid screening studies suggest that qacA-containing strains are transmitted among military personnel at Ft. Benning and that strains carrying qacA are associated with SSTIs within this population. The identification of a novel mechanism of qacA conjugative transfer among Staphylococcal strains suggests a possible future increase in the prevalence of antiseptic tolerant bacterial strains, and an increase in the rate of infections in settings where these agents are commonly used.

Keywords: antiseptic, Chlorhexedine digluconate, Staphycoccus aureus, plasmid acquisition, conjugation

Received: 13 Aug 2018; Accepted: 18 Oct 2018.

Edited by:

Katy Jeannot, UMR6249 Chrono Environnement, France

Reviewed by:

Yajun Song, Beijing Institute of Microbiology and Epidemiology, China
Edgardo Sepulveda, Ensenada Center for Scientific Research and Higher Education (CICESE), Mexico  

Copyright: © 2018 LaBreck, Rice, Paskey, Elassal, Cer, Law, Schlett, Bennett, Millar, Ellis, Hamilton, Bishop-Lilly and Merrell. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. D Scott Merrell, Department of Microbiology and Immunology, Uniformed Services University, Bethesda, United States, dmerrell@usuhs.mil