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ISAba1 mediated intrinsic chromosomal oxacillinase duplication conveys carbapenem resistance

ABSTRACT: Tandem duplication of carbapenemase genes amplifies the gene copy number and enhances carbapenem resistance. These amplifications are often heterogenous, transient, locate in plasmids, which often also contribute to heteroresistance. The duplication is especially important for low-hydrolysis activity enzymes, which is often overlooked or even under controversy. Here we reported an intrinsic oxacillinase duplication mediated by two neighbor ISAba1inserted in the same orientation. The duplication is relatively stable, located in chromosome, and the duplication times is up to twenty-five, much larger than previous reports. We provided genomic, transcriptomic, and proteomic evidence that the duplication resulted oxacillinase overproduction and thus contribute to carbapenem resistance. No other possible carbapenem resistance related changes (point mutations of oxaAb, disturbed expression of porin protein and efflux pump) were found during the duplication process. Furthermore, introducing oxaAb flanked by two ISAba1 to A. baumannii via plasmids, mimicked the in vivo duplication process under carbapenem stress. Taken together, ISAba1 mediated duplication of low activity intrinsic antibiotic hydrolysis enzymes could lead to antibiotic resistance for advanced-generation antibiotics.

ORGANISM(S): Acinetobacter Baumannii 470922

SUBMITTER: Guoqing Li

PROVIDER: PXD039528 | iProX | Tue Jan 17 00:00:00 GMT 2023

REPOSITORIES: iProX

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Project description:<p>The study of antimicrobial resistance (AMR) in infectious diarrhea has generally been limited to cultivation, antimicrobial susceptibility testing and targeted PCR assays. When individual strains of significance are identified, whole genome shotgun (WGS) sequencing of important clones and clades is performed. Genes that encode resistance to antibiotics have been detected in environmental, insect, human and animal metagenomes and are known as "resistomes". While metagenomic datasets have been mined to characterize the healthy human gut resistome in the Human Microbiome Project and MetaHIT and in a Yanomani Amerindian cohort, directed metagenomic sequencing has not been used to examine the epidemiology of AMR. Especially in developing countries where sanitation is poor, diarrhea and enteric pathogens likely serve to disseminate antibiotic resistance elements of clinical significance. Unregulated use of antibiotics further exacerbates the problem by selection for acquisition of resistance. This is exemplified by recent reports of multiple antibiotic resistance in Shigella strains in India, in Escherichia coli in India and Pakistan, and in nontyphoidal Salmonella (NTS) in South-East Asia. We propose to use deep metagenomic sequencing and genome level assembly to study the epidemiology of AMR in stools of children suffering from diarrhea. Here the epidemiology component will be surveillance and analysis of the microbial composition (to the bacterial species/strain level where possible) and its constituent antimicrobial resistance genetic elements (such as plasmids, integrons, transposons and other mobile genetic elements, or MGEs) in samples from a cohort where diarrhea is prevalent and antibiotic exposure is endemic. The goal will be to assess whether consortia of specific mobile antimicrobial resistance elements associate with species/strains and whether their presence is enhanced or amplified in diarrheal microbiomes and in the presence of antibiotic exposure. This work could potentially identify clonal complexes of organisms and MGEs with enhanced resistance and the potential to transfer this resistance to other enteric pathogens.</p> <p>We have performed WGS, metagenomic assembly and gene/protein mapping to examine and characterize the types of AMR genes and transfer elements (transposons, integrons, bacteriophage, plasmids) and their distribution in bacterial species and strains assembled from DNA isolated from diarrheal and non-diarrheal stools. The samples were acquired from a cohort of pediatric patients and controls from Colombia, South America where antibiotic use is prevalent. As a control, the distribution and abundance of AMR genes can be compared to published studies where resistome gene lists from healthy cohort sequences were compiled. Our approach is more epidemiologic in nature, as we plan to identify and catalogue antimicrobial elements on MGEs capable of spread through a local population and further we will, where possible, link mobile antimicrobial resistance elements with specific strains within the population.</p>

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ISAba1 mediated intrinsic chromosomal oxacillinase duplication conveys carbapenem resistance

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