Abhishek Kumar Shaw (Jena / DE), Lisa-Marie Karnbach (Jena / DE), Ariane Zander (Jena / DE), Marie-Luise Enghardt (Jena / DE), Marco Mauri (Jena / DE), Sharareh Tavaddod (Jena / DE), Vijay Srinivasan (Jena / DE), Rosalind Allen (Jena / DE; Edinburgh / GB)
Introduction: Emergence of antibiotic resistance is a major threat to global health, limiting the available options for treating infectious diseases. External factors such as nutrient richness or chemical composition of the media can influence the antibiotic stress response, survival, cellular adaptations, population dynamics and adaptive evolution of antibiotic tolerance and resistance in bacteria.
Goals: To investigate the influence of nutrient richness on Escherichia coli (E. coli) population growth dynamics and cellular stress response to rifampicin. Probability estimation and genetic analysis of the adaptive evolution of rifampicin resistance in E. coli.
Materials and methods: We investigated E. coli (BW25113) rifampicin susceptibility under nutrient rich and poor conditions (Neidhardt's MOPS rich or minimal medium, with added glucose) by quantitatively determining the population growth dynamics, frequency of pre-existing rifampicin resistance and denovo emergence of resistance, live cell microscopy and genetic sequencing of ancestral and evolved strains.
Results: Our investigation revealed contrasting growth dynamics on rich and poor media near the minimum inhibitory concentration of rifampicin. Under the nutrient poor condition, rifampicin led to reduced growth rate, whereas in the nutrient rich condition an extended lag phase was observed followed by stochastic exit from the lag phase, which also corresponded to the emergence of phenotypic rifampicin resistance. Further investigation revealed that the resistance emerged denovo under rifampicin treatment in the nutrient rich condition. We further investigated the cellular heterogeneity and genetic variations in the rifampicin resistance determining region of rpoB in the denovo rifampicin resistant strains.
Conclusions: Nutrient richness resulted in increased rifampicin extended lag phase, cellular heterogeneity and denovoemergence of rifampicin resistance in E. coli.