Reduction of the fitness cost of antibiotic resistance caused by chromosomal mutations under poor nutrient conditions

Effect of Environment on the Evolutionary Trajectories and Growth Characteristics of Antibiotic-Resistant Escherichia coli Mutants

“…We have found that media not only has a direct effect on the selection of spontaneous mutants conferring resistance to AMC in our experiments, but it also affects the competitive fitness of AMC-resistant strains selected for in LB, as has previously been acknowledged (Maharjan and Ferenci, 2017; Lin et al, 2018). Although both LB_2 and LB_5 contain the same mutation in the ampC promoter region which conferred resistance to AMC (Jaurin et al, 1982; Caroff et al, 2000), it is likely that either LB_5 has a compensatory mutation that allows it to grow better in ISO and M9 or there is a mutation elsewhere within the genome of the strains which results in a negative (for LB_2) or positive epistatic (for LB_5) interaction(s) only detectable during growth in ISO and M9 (Supplementary Table S1).…”

“…A similar phenomenon has previously been observed when competitive fitness was assessed in LB, M9, and tryptone soya broth following adaption of E. coli K12 MG1655 to LB to select for mutations that compensate for a loss of fitness following a mutation in either gyrA or marR (Basra et al, 2018). Both this study, ours and other previous studies (Maharjan and Ferenci, 2017; Lin et al, 2018; Yokoyama et al, 2018), highlight that mutations, and the associated fitness effects, can have different consequences in different environments.…”

“…It is known that the fitness cost of a particular mutation conferring resistance to an antibiotic is dependent on the environment it is assessed in, for example growth media (Maharjan and Ferenci, 2017; Lin et al, 2018), and another recent study investigated whether compensatory mutations that arise following acquisition of AMR genes by Escherichia coli had the same effect in different media; the results showed that such compensation does not always translate in another environment (Basra et al, 2018). This is an import finding, suggesting that a compensatory mutation can be beneficial in one physiological compartment, such as the bladder, but may be deleterious in another, for example the blood (Basra et al, 2018).…”

The Effect of Iodine-Containing Nano-Micelles, FS-1, on Antibiotic Resistance, Gene Expression and Epigenetic Modifications in the Genome of Multidrug Resistant MRSA Strain Staphylococcus aureus ATCC BAA-39

“…Firstly, the fitness cost for bacteria to maintain resistance is not always large enough to select for loss of the resistance alleles; therefore, even after removal of the drug, resistance may remain in the population for an extended period (Sjolund et al, 2003;Andersson and Hughes, 2010). Compensatory mutations and/or genetic regulatory mechanisms can also compensate for the large fitness cost of resistance by only activating resistance in the presence of the drug (Durão et al, 2018;Lin et al, 2018). Lastly, resistance mutations may provide the resistant strains with a fitness advantage by conferring increased virulence (Roux et al, 2015).…”

The Effect of Environmental Heterogeniety on the Fitness of Antibiotic Resistant Escherichia Coli

“…It has been previously shown that the costs associated with resistance could be influenced by environmental variation. For example, it has been suggested that productivity may impact costs, with higher nutrient environments imposing a higher cost for efflux over-expression mutants of Pseudomonas aeruginosa (Lin et al, 2018). It was shown that ciprofloxacin resistant P. aeruginosa strains had low productivity (CFU/ml) and lower fitness compared to the wild type strain in high nutrient conditions, and fitness and productivity increased as nutrient levels in the media decrease (Lin et al, 2018).…”