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Published on: December 27, 2016
Biofilms preserve the transmissibility of a multi-drug resistance plasmid
Genevieve A Metzger1,2,3, Benjamin J Ridenhour2,3,4, Michael France2,3
1Department of Biological Sciences, University of Idaho, Moscow, ID, USA.
Abstract:
Self-transmissible multidrug resistance (MDR) plasmids are a major health concern because they can spread antibiotic resistance to pathogens. Even though most pathogens form biofilms, little is known about how MDR plasmids persist and evolve in biofilms. We hypothesize that (i) biofilms act as refugia of MDR plasmids by retaining them in the absence of antibiotics longer than well-mixed planktonic populations and that (ii) the evolutionary trajectories that account for the improvement of plasmid persistence over time differ between biofilms and planktonic populations. In this study, we evolved Acinetobacter baumannii with an MDR plasmid in biofilm and planktonic populations with and without antibiotic selection. In the absence of selection, biofilm populations were better able to maintain the MDR plasmid than planktonic populations. In planktonic populations, plasmid persistence improved rapidly but was accompanied by a loss of genes required for the horizontal transfer of plasmids. In contrast, in biofilms, most plasmids retained their transfer genes, but on average, plasmid, persistence improved less over time. Our results showed that biofilms can act as refugia of MDR plasmids and favor the horizontal mode of plasmid transfer, which has important implications for the spread of MDR.
Insights
Biofilms protect multidrug resistance (MDR) plasmids from loss better than planktonic cells. Plasmids in biofilms retain transfer genes, aiding antibiotic resistance spread, unlike those in planktonic populations.
Area of Science:
- Microbiology
- Evolutionary Biology
- Genetics
Background:
- Self-transmissible multidrug resistance (MDR) plasmids contribute to the spread of antibiotic resistance in pathogens.
- Pathogenic bacteria frequently form biofilms, yet the role of biofilms in MDR plasmid dynamics remains unclear.
Purpose of the Study:
- To investigate if biofilms serve as refugia for MDR plasmids, enhancing their persistence.
- To compare the evolutionary trajectories of MDR plasmids in biofilm versus planktonic populations.
Main Methods:
- Evolved *Acinetobacter baumannii* with an MDR plasmid under both biofilm and planktonic conditions.
- Applied antibiotic selection and absence-of-selection conditions to assess plasmid persistence and evolution.
- Analyzed plasmid gene content, focusing on transfer genes and overall persistence.
Main Results:
- Biofilm populations maintained MDR plasmids longer than planktonic populations in the absence of antibiotics.
- Planktonic populations showed rapid plasmid persistence improvement but lost plasmid transfer genes.
- Biofilm populations retained plasmid transfer genes, though plasmid persistence improvement was slower.
Conclusions:
- Biofilms act as significant refugia for MDR plasmids, promoting their long-term maintenance.
- Biofilm environments favor horizontal plasmid transfer mechanisms, impacting the dissemination of antibiotic resistance.
- Understanding plasmid evolution in biofilms is crucial for combating the spread of multidrug resistance.
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