- Department of Mathematics and the Living Systems Institute, University of Exeter, Exeter, United Kingdom
- Cell Biology, Dynamical systems, Medical Sciences, Neuroscience, Physiology, Systems biology
Within-host evolutionary dynamics of antimicrobial quantitative resistance
Modelling within-host evolutionary dynamics of antimicrobial resistanceRecommended by Krasimira Tsaneva based on reviews by 2 anonymous reviewers
Antimicrobial resistance (AMR) arises due to two main reasons: pathogens are either intrinsically resistant to the antimicrobials, or they can develop new resistance mechanisms in a continuous fashion over time and space. The latter has been referred to as within-host evolution of antimicrobial resistance and studied in infectious disease settings such as Tuberculosis . During antibiotic treatment for example within-host evolutionary AMR dynamics plays an important role  and presents significant challenges in terms of optimizing treatment dosage. The study by Djidjou-Demasse et al.  contributes to addressing such challenges by developing a modelling approach that utilizes integro-differential equations to mathematically capture continuity in the space of the bacterial resistance levels.
Given its importance as a major public health concern with enormous societal consequences around the world, the evolution of drug resistance in the context of various pathogens has been extensively studied using population genetics approaches . This problem has been also addressed using mathematical modelling approaches including Ordinary Differential Equations (ODE)-based [5. 6] and more recently Stochastic Differential Equations (SDE)-based models . In  the authors propose a model of within-host AMR evolution in the absence and presence of drug treatment. The advantage of the proposed modelling approach is that it allows for AMR to be represented as a continuous quantitative trait, describing the level of resistance of the bacterial population termed quantitative AMR (qAMR) in . Moreover, consistent with recent experimental evidence  integro-differential equations take into account both, the dynamics of the bacterial population density, referred to as “bottleneck size” in  as well as the evolution of its level of resistance due to drug-induced selection.
The model proposed in  has been extensively and rigorously analysed to address various scenarios including the significance of host immune response in drug efficiency, treatment failure and preventive strategies. The drug treatment chosen to be investigated in this study, namely chemotherapy, has been characterised in terms of the level of evolved resistance by the bacterial population in presence of antimicrobial pressure at equilibrium.
Furthermore, the minimal duration of drug administration on bacterial growth and the emergence of AMR has been probed in the model by changing the initial population size and average resistance levels. A potential limitation of the proposed model is the assumption that mutations occur frequently (i.e. during growth), which may not be necessarily the case in certain experimental and/or clinical situations.
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 Djidjou-Demasse R, Sofonea MT, Choisy M, Alizon S (2021) Within-host evolutionary dynamics of antimicrobial quantitative resistance. HAL, hal-03194023, ver. 4 peer-reviewed and recommended by Peer Community in Mathematical and Computational Biology. https://hal.archives-ouvertes.fr/hal-03194023
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