WGS of Aeromonas isolates carrying mcr-3-related genes

WGS sequence of isolates positive for mcr-3-related and mcr-7-related genes.Study goals:Investigate the phylogenetic relationship between pet-A and mcr-3 genes in Aeromonas spp.Determine the level of polymyxin resistance imparted by transferable mcr-3-related genes in naive E. coli.Determine the presence of mcr-3, mcr-3-related and pet-A genes in environmental isolates and their relationship to mcr-3 genes from the literature.Brief summary of project and its goals:The study aims to explore the evolutionary relationship between chromosomal phosphoethanolamine lipid A transferases (pet-A), mcr-3-related /mcr-7-related genes and transferable (mcr*) polymyxin* resistance genes, focusing on mcr-3-related genes*. Evidence suggests that mcr-3-related genes, found on the chromosome of members of the Aeromonas spp. may be the missing link between chromosomal polymyxin resistance and its dissemination into the environment. The relationship will be determined by cloning mcr-3-related genes into a susceptible organism to assess functionality, utilising bioinformatics and phylogenetics to identify the genes prevalence in Aeromonas spp. This research is significant due to the emergence of transferable polymyxin resistance in normally susceptible Gram-negative organisms, highlighting the need to understand the dissemination of polymyxin resistance to combat multi-drug resistance.Relevance/significance:Resistance to modern antibiotics has emerged due to misuse in clinical and agricultural sectors. Polymyxins are an antibiotic class introduced in the 1950s that were discontinued during the 1980s due to neuro-/nephrotoxicity. Polymyxin B and E (colistin) were reintroduced in 1995 as a last resort treatment for multi-drug-resistant Gram-negative organisms. However in 2015, horizontally transferable colistin resistance was recorded in Enterobacteriaceae in China resulting from the mcr gene, which marked the first instance of transferable resistance in normally susceptible bacteria. Nine additional mcr variants have been discovered since 2015. This study focuses on mcr-3-related genes and their role in the evolutionary relationship between transferable mcr 3 and chromosomal pet-A in A. hydrophila. Aeromonas is the evolutionary origin point of mcr-3, however the mechanism behind its escape from the chromosome of Aeromonas remains unclear. There has been mcr-3-related genes with high nucleotide similarities to Enterobacteriaceae-sourced mcr-3 recorded on the chromosome of members of the Aeromonas spp., suggesting a potential link between pet-A and mcr-3. Literature on mcr-3-related gene encoded resistance and its implications for mcr-3s escape from the chromosome is sparse, with the relationship between mcr-3-related genes and pet-A remaining unclear. The emergence of transferable polymyxin resistance is clinically significant and of global concern as the number of effective antibiotics for treating multi-drug-resistant organisms diminishes, so understanding the underlying mechanisms and relationships behind transferable and chromosomal resistance genes is critical.