Biology subjects

ter Kuile, B. H.

Publications and source records attributed to ter Kuile, B. H..

3 recordsLinked to original sources

bioRxiv2024

Genetic Adaptation to Amoxicillin in Escherichia coli: The Limited Role of dinB and katE

Bacteria can quickly adapt to sub-lethal concentrations of antibiotics. Several stress and DNA repair genes contribute to this adaptation process. However, the pathways leading to adaptation by acquisition of de novo mutations remain poorly understood. This study explored the roles of DNA polymerase IV (dinB) and catalase HP2 (katE) in E. colis adaptation to amoxicillin. These genes are thought to play essential roles in beta-lactam resistance - dinB in increasing mutation rates and katE in managing oxidative stress. By comparing the adaptation rates, transcriptomic profiles, and genetic changes of wild-type and knockout strains, we aimed to clarify the contributions of these genes to beta-lactam resistance. While all strains exhibited similar adaptation rates and mutations in the frdD gene and ampC operon, several unique mutations were acquired in the {Delta}katE and {Delta}dinB strains. Overall, this study distinguishes the contributions of general stress-related genes on the one hand, and dinB, and katE on the other hand, in development of beta-lactam resistance.

microbiology↗

bioRxiv2024

De novo acquisition of antibiotic resistance in six species of bacteria

Bacteria can become resistant to antibiotics in two ways, by acquiring resistance genes through horizontal gene transfer and by de novo development of resistance upon exposure to non-lethal concentrations. The importance of the second process, de novo build-up, has not been investigated systematically over a range of species and may be underestimated as a result. To investigate the DNA mutation patterns accompanying the de novo antibiotic resistance acquisition process, six bacterial species encountered in the food chain were exposed to step-wise increasing sublethal concentrations of six antibiotics to develop high levels of resistance. Phenotypic and mutational landscapes were constructed based on whole genome sequencing (WGS) sequencing at two time points of the evolutionary trajectory. In this study, we found: 1) all of the six strains can develop high levels of resistance against most antibiotics. 2) increased resistance is accompanied by different mutations for each bacterium-antibiotic combination. 3) the number of mutations varies widely, with Y. enterocolitica having by far the most. 4) in the case of fluoroquinolone resistance, a mutational pattern of gyrA combined with parC is conserved in five of six species. 5) mutations in genes coding for efflux pumps are widely encountered in gram-negative species. The overall conclusion is that very similar phenotypic outcomes are instigated by very different genetic changes. IMPORTANCEThe significance of this study lies in the comparison of how six species of distinct genomic background under uniform conditions develop high levels of antibiotic resistance against six antibiotics. The mutational patterns in these six species of bacteria identify common target mutations and reveal how they acquire mutations from various pathways to survive and grow when exposed to sub-lethal levels of antibiotics. In addition to providing insights in microbial genetics, outcome of this study will assist policymakers when formulating practical strategies to prevent development of antimicrobial resistance in human and veterinary health care.

microbiology↗

bioRxiv2024

Progression of ampC amplification during de novo amoxicillin resistance development in E. coli

Beta-lactam antibiotics are the most applied antimicrobials in human and veterinarian health care. Hence, beta-lactam resistance is a major health problem. Gene amplification of AmpC beta-lactamase is a main contributor to de novo {beta}-lactam resistance in E. coli. However, the time course of amplification and the accompanying DNA mutations are unclear. Here, we study the progression of ampC amplification and ampC promoter mutations in the evolution of resistance by stepwise increasing amoxicillin concentration. AmpC promoter mutations occur by day two, while the amplification by a factor of approximately eight occurs after more than six days of amoxicillin exposure. The combination of amplification and promoter mutations increase ampC mRNA level by an average factor of 200 after 22 days. An IS1 insertion was identified in the amplification junction, suggesting the amplification is facilitated by mobile genetic elements transposition. In order to identify the essential genes for ampC amplification, the chromosomal mutations of strains with induced amoxicillin resistance were compared a similarly evolved resistant {Delta}ampC knockout. The evolved {Delta}ampC contained several resistance mutations that were absent in the WT, which accumulated more mutations in stress response genes. The amoxicillin evolved {Delta}ampC does not show amplification of the fragment around the original ampC position but exhibits a large duplication or triplication at another position, suggesting selection of genes to amplify is essential for resistance adaption. IMPORTANCEAmoxicillin is one of the most used antimicrobial against bacterial infections. DNA fragments containing ampC are amplified upon prolonged and stepwise increasing exposure to amoxicillin. These ampC amplification fragments have been identified in extended-spectrum beta-lactamases (ESBLs) plasmids, which are considered the main cause of beta- lactam resistance. Understanding the progression of ampC amplification enables amoxicillin resistance prevention. In this study, we show the time course of two important factors for ampC transcription enhancement, ampC amplification and ampC promoter mutations, during de novo amoxicillin resistance evolution. We propose that the transposon IS1 contributes to the amplification and that the sigma factor 70 regulates ampC overexpression.

microbiology↗