Session Type: 1-hour ePoster Review
Session Title: 1-hour ePoster Review
Authors(s): J. Zhao (1), Y. Zhu (1), Y.W. Lin (1), H. Yu (1), H. Wickremasinghe (1), T. Velkov (2), M. Mcdonald (3), J. Li (1)
Authors Affiliations(s): (1) Infection & Immunity Program, Department of Microbiology, Biomedicine Discovery Institute, Monash University, Australia, (2) Department of Pharmacology and Therapeutics, University of Melbourne, Australia, (3) School of Biological Sciences, Monash University, Australia
Background:
Polymyxins are a last-line therapy for treating life-threatening infections caused by MDR A. baumannii. Alarmingly, polymyxin resistance is increasingly reported globally, while translation of the dynamics of resistance mutations into evolutionary outcomes under different polymyxin treatment strategies has not been thoroughly investigated. Here, we investigated how polymyxin concentrations induced the genetic interactions in polymyxin resistance in A. baumannii and in turn, how the genetic interactions shaped the population dynamics.
Methods:An in vitro evolution experiment of A. baumannii AB5075 (an MDR clinical isolate and type strain) was conducted in a fluctuating condition that alternated between growth in media with or without polymyxin B evolution treatments. Population analysis profiles (PAPs) were conducted for all samples and whole population sequencing on Illumina HiSeq was conducted at multiple time points. Mutations and insertions were detected by Freebays and MGEfinder, respectively; and pathway analysis was performed using BioCyc.
Results:PAPs results revealed that populations from lower concentration evolution treatments (i.e. 0.5 and 1×MIC) were reversibly resistant to up to 64×MIC polymyxin B. Conversely, the 4, 8 and 16×MIC evolution treatment populations evolved non-reversible polymyxin resistance (e.g. up to 128×MIC), suggesting that 4×MIC evolution treatment represents a critical threshold related to high, non-reversible resistance. Whole genome sequencing results proved this finding and showed a significant variation in the numbers of non-synonymous mutations across treatment populations, with a strong and significant correlation with polymyxin concentration. Multi-hit mutations and parallel evolution analysis identified both nonsynonymous mutations in pmrB and genes related to cell envelope biogenesis (e.g. fimD, wecBC and ABUW_3081), and unique insertions (e.g. lpxA, pfpA) in populations treated with ≥ 4×MIC polymyxin B. These results revealed that polymyxin resistance caused significant membrane disorganisation and remodelling in A. baumannii.
Conclusions:This is the first evolution study using whole population sequencing to provide mechanistic understanding of polymyxin resistance in A. baumannii. The strength of the selective pressure by polymyxin B tunes the dynamics of genetic variations within the population, leading to different evolutionary outcomes for the degree, cost and reversibility of resistance. Our findings provide key mechanistic understanding for optimisation of polymyxin use in patients.
Keyword(s): polymyxin resistance, evolutionary dynamics, Acinetobacter baumanniiCOI Institutional Grants: Yes
Session Type: 1-hour ePoster Review
Session Title: 1-hour ePoster Review
Authors(s): J. Zhao (1), Y. Zhu (1), Y.W. Lin (1), H. Yu (1), H. Wickremasinghe (1), T. Velkov (2), M. Mcdonald (3), J. Li (1)
Authors Affiliations(s): (1) Infection & Immunity Program, Department of Microbiology, Biomedicine Discovery Institute, Monash University, Australia, (2) Department of Pharmacology and Therapeutics, University of Melbourne, Australia, (3) School of Biological Sciences, Monash University, Australia
Background:
Polymyxins are a last-line therapy for treating life-threatening infections caused by MDR A. baumannii. Alarmingly, polymyxin resistance is increasingly reported globally, while translation of the dynamics of resistance mutations into evolutionary outcomes under different polymyxin treatment strategies has not been thoroughly investigated. Here, we investigated how polymyxin concentrations induced the genetic interactions in polymyxin resistance in A. baumannii and in turn, how the genetic interactions shaped the population dynamics.
Methods:An in vitro evolution experiment of A. baumannii AB5075 (an MDR clinical isolate and type strain) was conducted in a fluctuating condition that alternated between growth in media with or without polymyxin B evolution treatments. Population analysis profiles (PAPs) were conducted for all samples and whole population sequencing on Illumina HiSeq was conducted at multiple time points. Mutations and insertions were detected by Freebays and MGEfinder, respectively; and pathway analysis was performed using BioCyc.
Results:PAPs results revealed that populations from lower concentration evolution treatments (i.e. 0.5 and 1×MIC) were reversibly resistant to up to 64×MIC polymyxin B. Conversely, the 4, 8 and 16×MIC evolution treatment populations evolved non-reversible polymyxin resistance (e.g. up to 128×MIC), suggesting that 4×MIC evolution treatment represents a critical threshold related to high, non-reversible resistance. Whole genome sequencing results proved this finding and showed a significant variation in the numbers of non-synonymous mutations across treatment populations, with a strong and significant correlation with polymyxin concentration. Multi-hit mutations and parallel evolution analysis identified both nonsynonymous mutations in pmrB and genes related to cell envelope biogenesis (e.g. fimD, wecBC and ABUW_3081), and unique insertions (e.g. lpxA, pfpA) in populations treated with ≥ 4×MIC polymyxin B. These results revealed that polymyxin resistance caused significant membrane disorganisation and remodelling in A. baumannii.
Conclusions:This is the first evolution study using whole population sequencing to provide mechanistic understanding of polymyxin resistance in A. baumannii. The strength of the selective pressure by polymyxin B tunes the dynamics of genetic variations within the population, leading to different evolutionary outcomes for the degree, cost and reversibility of resistance. Our findings provide key mechanistic understanding for optimisation of polymyxin use in patients.
Keyword(s): polymyxin resistance, evolutionary dynamics, Acinetobacter baumanniiCOI Institutional Grants: Yes
Session Type: 1-hour ePoster Review
Session Title: 1-hour ePoster Review
Authors(s): J. Zhao (1), Y. Zhu (1), Y.W. Lin (1), H. Yu (1), H. Wickremasinghe (1), T. Velkov (2), M. Mcdonald (3), J. Li (1)
Authors Affiliations(s): (1) Infection & Immunity Program, Department of Microbiology, Biomedicine Discovery Institute, Monash University, Australia, (2) Department of Pharmacology and Therapeutics, University of Melbourne, Australia, (3) School of Biological Sciences, Monash University, Australia
Background:
Polymyxins are a last-line therapy for treating life-threatening infections caused by MDR A. baumannii. Alarmingly, polymyxin resistance is increasingly reported globally, while translation of the dynamics of resistance mutations into evolutionary outcomes under different polymyxin treatment strategies has not been thoroughly investigated. Here, we investigated how polymyxin concentrations induced the genetic interactions in polymyxin resistance in A. baumannii and in turn, how the genetic interactions shaped the population dynamics.
Methods:An in vitro evolution experiment of A. baumannii AB5075 (an MDR clinical isolate and type strain) was conducted in a fluctuating condition that alternated between growth in media with or without polymyxin B evolution treatments. Population analysis profiles (PAPs) were conducted for all samples and whole population sequencing on Illumina HiSeq was conducted at multiple time points. Mutations and insertions were detected by Freebays and MGEfinder, respectively; and pathway analysis was performed using BioCyc.
Results:PAPs results revealed that populations from lower concentration evolution treatments (i.e. 0.5 and 1×MIC) were reversibly resistant to up to 64×MIC polymyxin B. Conversely, the 4, 8 and 16×MIC evolution treatment populations evolved non-reversible polymyxin resistance (e.g. up to 128×MIC), suggesting that 4×MIC evolution treatment represents a critical threshold related to high, non-reversible resistance. Whole genome sequencing results proved this finding and showed a significant variation in the numbers of non-synonymous mutations across treatment populations, with a strong and significant correlation with polymyxin concentration. Multi-hit mutations and parallel evolution analysis identified both nonsynonymous mutations in pmrB and genes related to cell envelope biogenesis (e.g. fimD, wecBC and ABUW_3081), and unique insertions (e.g. lpxA, pfpA) in populations treated with ≥ 4×MIC polymyxin B. These results revealed that polymyxin resistance caused significant membrane disorganisation and remodelling in A. baumannii.
Conclusions:This is the first evolution study using whole population sequencing to provide mechanistic understanding of polymyxin resistance in A. baumannii. The strength of the selective pressure by polymyxin B tunes the dynamics of genetic variations within the population, leading to different evolutionary outcomes for the degree, cost and reversibility of resistance. Our findings provide key mechanistic understanding for optimisation of polymyxin use in patients.
Keyword(s): polymyxin resistance, evolutionary dynamics, Acinetobacter baumanniiCOI Institutional Grants: Yes
Session Type: 1-hour ePoster Review
Session Title: 1-hour ePoster Review
Authors(s): J. Zhao (1), Y. Zhu (1), Y.W. Lin (1), H. Yu (1), H. Wickremasinghe (1), T. Velkov (2), M. Mcdonald (3), J. Li (1)
Authors Affiliations(s): (1) Infection & Immunity Program, Department of Microbiology, Biomedicine Discovery Institute, Monash University, Australia, (2) Department of Pharmacology and Therapeutics, University of Melbourne, Australia, (3) School of Biological Sciences, Monash University, Australia
Background:
Polymyxins are a last-line therapy for treating life-threatening infections caused by MDR A. baumannii. Alarmingly, polymyxin resistance is increasingly reported globally, while translation of the dynamics of resistance mutations into evolutionary outcomes under different polymyxin treatment strategies has not been thoroughly investigated. Here, we investigated how polymyxin concentrations induced the genetic interactions in polymyxin resistance in A. baumannii and in turn, how the genetic interactions shaped the population dynamics.
Methods:An in vitro evolution experiment of A. baumannii AB5075 (an MDR clinical isolate and type strain) was conducted in a fluctuating condition that alternated between growth in media with or without polymyxin B evolution treatments. Population analysis profiles (PAPs) were conducted for all samples and whole population sequencing on Illumina HiSeq was conducted at multiple time points. Mutations and insertions were detected by Freebays and MGEfinder, respectively; and pathway analysis was performed using BioCyc.
Results:PAPs results revealed that populations from lower concentration evolution treatments (i.e. 0.5 and 1×MIC) were reversibly resistant to up to 64×MIC polymyxin B. Conversely, the 4, 8 and 16×MIC evolution treatment populations evolved non-reversible polymyxin resistance (e.g. up to 128×MIC), suggesting that 4×MIC evolution treatment represents a critical threshold related to high, non-reversible resistance. Whole genome sequencing results proved this finding and showed a significant variation in the numbers of non-synonymous mutations across treatment populations, with a strong and significant correlation with polymyxin concentration. Multi-hit mutations and parallel evolution analysis identified both nonsynonymous mutations in pmrB and genes related to cell envelope biogenesis (e.g. fimD, wecBC and ABUW_3081), and unique insertions (e.g. lpxA, pfpA) in populations treated with ≥ 4×MIC polymyxin B. These results revealed that polymyxin resistance caused significant membrane disorganisation and remodelling in A. baumannii.
Conclusions:This is the first evolution study using whole population sequencing to provide mechanistic understanding of polymyxin resistance in A. baumannii. The strength of the selective pressure by polymyxin B tunes the dynamics of genetic variations within the population, leading to different evolutionary outcomes for the degree, cost and reversibility of resistance. Our findings provide key mechanistic understanding for optimisation of polymyxin use in patients.
Keyword(s): polymyxin resistance, evolutionary dynamics, Acinetobacter baumanniiCOI Institutional Grants: Yes