Thein vitrofitness cost of antimicrobial resistance inEscherichia colivaries with the growth conditions

Abstract

The objective of this study was to investigate the influence of stressful growth conditions on the fitness cost of antimicrobial resistance in Escherichia coli BJ4 caused by chromosomal mutations and plasmid acquisition. The fitness cost of chromosomal streptomycin resistance increased significantly when the bacteria were grown under all stress conditions tested, while the cost in 1/3 Luria-Bertani was not significantly changed in a streptomycin+rifampicin mutant. The increase in the fitness cost depended in a nonregular manner on the strain/stress combination. The fitness cost of plasmid-encoded resistance on R751 did not differ significantly, and was generally less under stressful growth conditions than in rich media. The fitness cost associated with R751 with the multiple drug resistance cassette from Salmonella Typhimurium DT104 increased significantly only under stressful conditions at low pH and at high-salt concentrations. Strains with an impaired rpoS demonstrated a reduced fitness only during growth in a high-salt concentration. In conclusion, it was demonstrated that bacterial fitness cost in association with antimicrobial resistance generally increases under stressful growth conditions. However, the growth potential of bacteria with antimicrobial resistances did not increase in a straightforward manner in these in vitro experiments and is therefore probably even more difficult to predict in vivo.

Increased Survival of Antibiotic-Resistant Escherichia coli inside Macrophages

“…It was previously demonstrated that fitness effects for the reproduction of antibiotic-resistant bacteria generally increase under stressful conditions (14,55). The effects on the reproduction of more than half (58%) of the antibiotic-resistant mutants were either neutral or slightly advantageous in the presence of the Ms; however, this was mainly attributed to growth in the RPMI cell culture medium that we used for the maintenance of eukaryotic cells.…”

A cooperative virulence plasmid imposes a high fitness cost under conditions that induce pathogenesis

“…These costs can vary depending on external environmental conditions [28,29], the genetic background of the cell that harbours them [27] or the population frequency of the plasmid [8]. Cost of cooperative virulence plasmid T. G. Platt et al 1695 In this study, we demonstrated that there is a fitness cost associated with the carriage of the A. tumefaciens virulence plasmid under resource-limiting conditions.…”

Fitness costs of various mobile genetic elements in Enterococcus faecium and Enterococcus faecalis

“…Alternatively, the experimental conditions may have favoured the plasmid–strain association, and the results might have been different under more stressful conditions, as demonstrated for Escherichia coli. 43 It also remains to be elucidated whether there is a correlation between (replicase-determined) plasmid classes and fitness effects since our experiments, performed with only a limited number of strains and plasmids, do not allow us to draw general conclusions.…”