The delftia integrons comprised a highly conserved class 3 integrase gene, upstream and oppositely oriented from a set of three or four gene. This study described the antibiotic susceptibility and the presence of class 1 and 2 integrons in s. In this study, by using clone library analysis and highthroughput sequencing. Resistance patterns and integron cassette arrays of. Insertion elements, transposons, and integrons are described in the. Integrons are mobile dna elements and they have an important role in acquisition and dissemination of antimicrobial resistance genes. May 18, 2017 vimtype enzyme encodes the most widely acquired metallo. Their ability to rapidly spread resistance phenotypes makes it important to consider what other integronmediated traits might impact human health in the future, such as increased virulence. The evolution of class 1 integrons and the rise of antibiotic. The evolution of class 1 integrons and the rise of antibiotic resistance. Bacteria have existed from very early in the history of life on earth. The molecular background to this surprising development was investigated by using pcr to screen for integrons and specific resistance genes, followed by sequence analysis of selected integrons, in 105 clinical urinary isolates of gramnegative bacteria selected partly for. The human and animal intestinal tract harbors a complex community of microbes which enables bacteria to inherit antibiotic resistance genes.
Integrons are genetic elements that acquire and exchange exogenous dna, known as gene cassettes, by a sitespecific recombination mechanism. Insights and inferences about integron evolution from genomic data. Characterization of the novel in1059 harbouring vim gene. Genomic islands are nonselfmobilizing integrative and excisive elements that encode diverse functional characteristics but all contain a recombination module comprised of an integrase, associated attachment sites and, in some cases, a recombination.
Integrons also occur in the chromosomes of many bacteria, notably. They play a major role in the dissemination of antibiotic resistance among gramnegative bacteria. Class 1 integrons were shown to be capable of accessing this gene pool through tests of recombinational activity with a representative range of egcs. More recently, their role in genome evolution has been extended with the discovery of larger integron structures, the super integrons, as genuine components of the genomes of many species throughout the. The molecular background to this surprising development was investigated by using pcr to screen for integrons and specific resistance genes, followed by sequence analysis of selected integrons, in 105 clinical urinary isolates of gramnegative bacteria selected partly. The gene cassettes may encode genes for antibiotic resistance, although most genes in integrons are uncharacterized. Integrons are dna elements with major involvement in the spread of antibioticresistant genes through horizontal or vertical gene transfer mechanisms 5 mazel d. Cassettes usually contain only one gene, potentially any gene, and an attc recombination site, and thousands of cassettes have been sequenced. They capture genes by using integrasemediated sitespecific recombination of mobile gene cassettes. Insertion elements, transposons, and integrons are described in the context of their mechanisms and role in evolution. Class 1 integrons are central players in the worldwide problem of antibiotic resistance, because they can capture and express diverse resistance genes.
Chromosomally located integrons ci have been identified in a large number of environmental gramnegative bacteria. Genomic islands are dynamic, ancient integrative elements. Class 1 integrons are genetic systems that enable bacteria to capture and express gene cassettes. Among the genetic elements, integrons may contribute to the widespread incidence and spreading of antibiotic resistance among escherichia coli isolates. We propose that gene cassettes represent a vast, prepackaged genetic resource that could be thought of as a. The use of the covariance model confirmed that attc sites are more similar within than between integrons. Impact of wastewater treatment on the prevalence of. Integrons are genetic units found in many bacterial species that are defined by their ability to capture small mobile elements called gene cassettes. They are ancient elements that are a hot spot for genomic complexity, generating phenotypic diversity and shaping adaptive responses. The evolutionary history of chromosomal superintegrons.
A the integron is composed of a specific integron integrase gene inti, orange, an atti recombination site red, and an array of gene cassettes blue, yellow and green. Bacteria fossils discovered in rocks date from at least the devonian period 419. A total of 200 uropathogenic upec and diarrheagenic escherichia coli dec isolates from outpatients were investigated for antimicrobial susceptibility and the presence of class 1, 2, and 3 integronassociated integrase inti genes and gene cassettes. The aims of this study were to investigate clonality, antimicrobial resistance, prevalence and gene cassette arrays of class i and ii integrons among commensal escherichia coli from human and animals. Although sequencing of cellular genomes first revealed a more prominent role for hgt in bacterial evolution than previously recognized, until recently, genome sequencing and analysis of the agents. Use of chromosomal integron arrays as a phylogenetic typing system for vibrio cholerae pandemic strains. Impacts of anthropogenic activity on the ecology of class. The integron is a powerful system which, by capturing, stockpiling, and rearranging new functions carried by gene encoding cassettes, confers upon bacteria a rapid adaptation capability in changing environments. The evolution of class 1 integrons and the rise of. These genes are embedded in a specific genetic structure called gene cassette a term that is lately changing to integron cassette that generally carries one promoterless open reading frame orf together with a recombination site attc. Integron identification in bacterial genomes and cassette. Characterization of the resistance class 1 integrons in.
Integrons are mechanisms that facilitate horizontal gene transfer, allowing bacteria to integrate and express foreign dna. One cassette was identical to a previously described cassette from a chromosomal class 3 integron in delftia tsuruhatensis. May 31, 2008 integrons are mechanisms that facilitate horizontal gene transfer, allowing bacteria to integrate and express foreign dna. Reconstructing the history of class 1 integrons might help us control further spread of antibiotic resistance by understanding how human activities influence microbial evolution. Genomic islands are dynamic, ancient integrative elements in. The evolution of multiple novel and complex gene cassettes in integrons further suggests the selection and horizontal transfer of args in multidrug resistant bacteria. Integrons are genetic elements able to acquire and rearrange open reading frames orfs embedded in gene cassette units and convert them to functional genes by ensuring their correct expression. The human intestinal microbiota plays a major beneficial role in immune development and resistance to pathogens.
The occurrence and prevalence of integrons in clinical microorganisms and their role played in antimicrobial resistance have been well studied recently. Integrons are genetic elements composed of a gene encoding an integrase, gene cassettes and an integration site for the gene cassettes att. The term superintegron was first applied in 1998 but without definition to the integron with a long cassette array on the small chromosome of vibrio cholerae. Antimicrobial resistance and integron gene cassette arrays.
Two environmental strains, delftia acidovorans c17 and delftia tsuruhatensis a90, were found to carry class 3 integrons, which have seldom been reported and then only from pathogens in which they are associated with antibiotic resistance genes. Understanding the origin of these elements is important for the practical control of antibiotic. Characterization of the novel in1059 harbouring vim gene cassette. With the recent release of many new treponema genomes, we were able to study the distribution of chromosomal.
Antimicrobial resistance patterns and prevalence of class 1. Integron analysis is also useful to study bacterial evolution and gene transfer because these elements can pass from bacterium to bacterium during conjugation. The stringent response promotes antibiotic resistance. The emergence and spread of antibiotic resistance among bacterial pathogens is the. To address this knowledge gap, bovine mastitisinducing s. They were originally identified as a mechanism used by gramnegative bacteria to collect antibiotic resistance genes and express multiple resistance phenotypes in synergy with transposons. Gene cassettes are discrete genetic elements that may exist as free, circular, nonreplicating dna molecules when moving from one genetic site to another, 3 but which are normally found as linear sequences that constitute part of a larger dna molecule, such as a plasmid or bacterial chromosome. Hall rm, collis cm 1995 mobile gene cassettes and integrons.
Jan 22, 20 integron systems are now recognized as important agents of bacterial evolution and are prevalent in most environments. A cassette is typically composed of an orf flanked by two attc recombination sites. The resistance for each antibiotic, except imipenem, was significantly associated with the presence of integrons. Integrons and gene cassettes in clinical isolates of co. The affiliation of multiresistant integrons mris, which contain.
Treatment with effective antibiotics is recommended for shigellosis, but options become limited due to globally emerging resistance. Antimicrobial resistance patterns and prevalence of class. Impact of wastewater treatment on the prevalence of integrons. However, there are limited data available on integrons of staphylococcus aureus s. As mentioned above, the main bacterial chromosome can exhibit quite dynamic reorganization following the insertion or deletion of transposons, integrons and genomic islands under fluctuating environmental and selective conditions. The determination of resistance towards eight classes of. Natural transformation facilitates transfer of transposons. Integrons are a peculiar group of genetic elements consisting of an integrase gene and a nearby recombination site at which mobile gene cassettes can be directionally inserted or excised by a sitespecific recombination mechanism catalyzed by the integron integrase. We propose that gene cassettes represent a vast, prepackaged genetic resource that could be thought of as a metagenomic template for bacterial evolution. Integrons are considered to play a significant role in the evolution and spread of antimicrobial resistance genes. Vimtype enzyme encodes the most widely acquired metallo. To obtain current epidemiological data for integrons from enterobacteriae in hospital, the study characterizes the genetic structure in in1059 by comparison with in846 integrons harbouring vim gene and other class 1 integrons including in37, in62, in843 and in1021 with the aim of identifying the.
These are important in the exchange of antibiotic resistance determinants, but can also transfer a diverse suite of genes unrelated to pathogenicity. Integrons are genetic elements involved in bacterial adaptation to the environment. The integrase excises and integrates the gene cassettes from and into the integron, but integrons themselves are not mobile. An attc sequence also called 59be is a repeat that flanks cassettes and enables cassettes to be integrated at the atti site, excised and undergo horizontal gene transfer. Full text the full text of this article is available as a pdf 212k. Their ability to rapidly spread resistance phenotypes makes it important to consider what other integron mediated traits might impact human health in the future, such as increased virulence. Preclinical class 1 integron with a complete tn402like. Integrons and antibiotic resistance genes in waterborne.
A broadhostrange, generalized transducing phage snt acquires 16s rrna genes from different genera of bacteria. Our study sheds new light on the evolution of integrons. There were at least two important steps leading to the generation of the basic class 1 integron backbone that now dominates clinical isolates in the antibiotic era 3, 20. Jan 16, 2001 integrons are genetic elements that acquire and exchange exogenous dna, known as gene cassettes, by a sitespecific recombination mechanism. Integron evolutionary history suggests that these sedentary cis. Acquisition of genomic islands plays a central part in bacterial evolution as a mechanism of diversification and adaptation. Shigella is a frequent cause of bacterial dysentery in the developing world. The integron platform allows the acquisition, expression, and dissemination of antibiotic resistance genes within gene cassettes. Class 1 integrons have played a major role in the global dissemination of antibiotic resistance. Towner, in medical microbiology eighteenth edition, 2012.
The gain and loss of chromosomal integron systems in the. Metagenomic libraries identify the entire genetic complement of newly discovered life forms, without the need to culture the organisms. The first of these was the insertion of the integron into a tn402like. It also uncovered a positive association between the homogeneity of attc sites and the number of cassettes in integrons. Impacts of anthropogenic activity on the ecology of class 1. The integron integrase has its own promoter p inti. The presence of integrons was assessed in gut bacteria isolated from wildcaught prawns. Impacts of anthropogenic activity on the ecology of class 1 integrons and integronassociated genes in the environment. In addition, they are often embedded in promiscuous plasmids and transposons, facilitating their lateral transfer into a wide range of pathogens. These integrons, when isolated in clinical contexts, most often carry antibiotic resistance gene cassettes. Transposons are linear pieces of dna, often including. Genomic islands are nonselfmobilizing integrative and excisive elements that encode diverse functional characteristics but all contain a recombination module comprised of an integrase, associated attachment sites and, in some cases, a recombination directionality factor.
Wastewater treatment plants wwtps contain abundant resistance genes. Insights and inferences about integron evolution from. In a survey of xanthomonas, integrons were found in all 32 strains representing 12 pathovars of two species. Sedentary chromosomal integrons scis can stockpile and rearrange a myriad of different functions encoded in gene cassettes. Integrons are bacterial genetic elements that can capture, rearrange, and express mobile gene cassettes. Integrons are versatile gene acquisition systems commonly found in bacterial genomes. Integrons were first identified as the primary mechanism for antibiotic resistance gene capture and dissemination among gramnegative bacteria. Identification and analysis of integrons and cassette arrays. Integrons are best known for assembling antibiotic resistance genes in clinical bacteria. Prevalence of class 1 integron in escherichia coli.
Despite a trend of declining consumption, resistance to cotrimoxazole has increased during a 12year period in stockholm. Integrons are genetic mechanisms that allow bacteria to adapt and evolve rapidly through the stockpiling and expression of new genes. A pseudomonad was recovered that contained a tn 402 like class 1 integron with a complete transposition module and two gene cassettes. The class 1 integrons are of great clinical importance, being responsible for the ongoing accumulation of antibiotic resistance genes 14, 15, 17, 18. The delftia integrons comprised a highly conserved class 3 integrase gene, upstream and oppositely oriented from a set of three or four gene cassettes. Reported as widely spread and distributed in clinical organisms, the mobility of integrons has been considered to be a major concern of clinically antibiotic resistance, which is defined as being associated with mobile dna elements transposons or plasmids and antibioticresistance genes in addition to having a small array size and substantial heterogeneity in the sequence of attc sites 7. The aim of this research was to analyse the resistance patterns and characterize the distribution and genetic content of resistance integrons within enterobacter cloacae complex strains originating from hospitalized patients. The emergence and spread of antibiotic resistance among bacterial pathogens is the most striking example of evolution that has. Antibioticresistant genes args are regarded as emerging environmental pollutants and pose a serious health risk to the human population. Identification and analysis of integrons and cassette. Jan, 2020 integrons are bacterial genetic elements that can capture, rearrange, and express mobile gene cassettes. As screening and detection of integrons are concerned, current diagnostic methodologies are restricted by significant drawbacks and novel methods are required for integrons detection.
They are best known for their role in disseminating antibioticresistance genes among pathogens. This systematic literature search was performed from january 1, 2000 to the end of may 1, 2019. Prevalence of class 1 integron in escherichia coli isolated. Integron systems are now recognized as important agents of bacterial evolution and are prevalent in most environments. To obtain current epidemiological data for integrons from enterobacteriae in hospital, the study characterizes the genetic structure in in1059 by comparison with in846 integrons harbouring vim gene and other class 1 integrons including in37, in62, in843 and in1021 with the aim of identifying. Molecular characterization of class 3 integrons from delftia. Distribution of class 1 and 2 integrons among salmonella. Pdf class 1 integrons have played a major role in the global dissemination of antibiotic resistance.
Distribution of integrons and gene cassettes among. They also act as reservoirs of these resistance traits, further contributing to the development of multidrug resistance in several waterborne pathogens. Here, we provide a systematic analysis of the distribution and diversity of integron inti genes and integroncontaining. Insights and inferences about integron evolution from genomic. Pathogens free fulltext integrons in the intestinal. One of the human pathogens known to harbor chromosomal integrons, the treponema spirochetes are the only clade among spirochete species found to carry integrons. Schema of an integron and the three types of elements detected by integronfinder.
Nyas publications the new york academy of sciences. The key element of integrons is the integrase, which allows gene cassettes to be acquired. Gene cassettes normally contain only a single gene. The use of antibiotics, however, can cause the spread of antibiotic resistance genes within the resident intestinal microbiota. Characterized gene cassettes consist of a target recombination sequence attc site usually associated with a single open reading frame coding for an antibiotic resistance determinant. Here we describe a class 1 integron that represents an intermediate stage in the evolutionary history of clinical integrons. Jun 21, 2002 also discussed are the bacterial restriction. One of the mechanisms for the development of resistance utilizes integrons. Here we describe a class 1 integron that represents an intermediate stage in the evolutionary history of clinical.
Oct 20, 2015 reported as widely spread and distributed in clinical organisms, the mobility of integrons has been considered to be a major concern of clinically antibiotic resistance, which is defined as being associated with mobile dna elements transposons or plasmids and antibioticresistance genes in addition to having a small array size and substantial heterogeneity in the sequence of attc sites 7. Thus, the detection and characterization of these integrons in waterborne pathogens, especially in epidemic and pandemic strains, is of the utmost importance. Integrons are genetic elements that are involved in the spread of args amongst bacterial species. Molecular characterization of class 3 integrons from. The gene cassette metagenome is a basic resource for. Jan 21, 2009 acquisition of genomic islands plays a central part in bacterial evolution as a mechanism of diversification and adaptation.
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