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Postdoc Spotlight: Behavioral resistance, antibiotic resistance, and immune tradeoffs

In this special Club EvMed, we highlighted some of the exciting work done by postdoctoral researchers in the field of evolutionary medicine. We heard 12-minute research talks from Caroline Amoroso, Amrita Bhattacharya, and Angela Garcia (see abstracts and time stamps below) with a brief Q&A period at the end of each talk, plus breakout rooms after all 3 talks to allow for more in depth conversations with the speakers (not part of the below recording).

Caroline Amoroso presenting a virtual talkEvolution of host behavioral resistance to pathogens” by Caroline Amoroso, University of Virginia (view at 1:11). Evolutionary theory about host resistance to pathogens has typically focused on physiological mechanisms of resistance, yet strategies that hosts use to prevent pathogen infection can also be behavioral. Using a framework established in previous work on physiological resistance, I develop a model of behavioral resistance to a socially transmitted disease and use it to explore evolutionary dynamics under different assumptions about the avoidance strategy and nature of costs. I discuss the parallels between behavioral and physiological forms of resistance, and the limitations of physiological resistance theory for explaining the evolution and disease dynamics of behavioral resistance.

Amrita Bhattacharya presenting a virtual talkExceptions to the rule: Why does resistance evolution not undermine antibiotic therapy in all bacterial infections?” by Amrita Bhattacharya, Pennsylvania State University (view at 17:41). Antibiotic resistance is among the greatest public health crises of the 21st century, but the phenomenon of resistance evolution is not surprising. Antibiotics impose strong selective pressure on bacteria to survive, reproduce, and transmit in their presence leading to the evolution of antibiotic resistance. Yet not all human bacterial infections are affected by resistance evolution. Why? Here we attempt to understand (a) in which cases resistance evolution has not undermined treatment-efficacy, and (b) which factors, if any, can explain these patterns of resistance evolution. We are surveying the scientific literature over the last five years to determine variation in the prevalence of resistance across 57 species of human bacterial pathogens and the subset of 79 antibiotics from 15 different drug classes used to treat them. We examine the variation in resistance across these ‘pathogen x antibiotic’ combinations, and determine how factors such as mechanism of drug action, pathogen classification, mode of transmission, human-to-human transmission, presence of pathogen in the human microbiome, natural competence, and aerobic/anaerobic growth correlate with the observed patterns of resistance.

Angela Garcia presenting a virtual talkEvidence for height and immune function trade-offs among pre-adolescents in a high pathogen population” by Angela Garcia, Arizona State University (view at 34:13). In an energy-limited environment, investment in one trait should trade-off with investment in other traits. In high pathogen ecologies, biasing energy allocation towards immunity over growth would be predicted, given strong selective pressures against early-life mortality. Here, I examine trade-offs between adaptive immune and height among young children in the Bolivian Amazon. Tracking tradeoffs between growth and immune function is enormously complex, particularly due to the changing relationships between distribution of body fat and mass relative to height, and shifts in allocation between life history traits, that occur during this period of active growth and development. However, the consistent negative associations across the numerous markers of adaptive immune function and height-for-age documented in this research prompt consideration of whether there may be a threshold of investment into adaptive immune function required for survival in high pathogen environments.

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