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Class I integrons have garnered significant attention due to pivotal roles in the dissemination of antimicrobial resistance genes (ARGs), which impose risks to public health and food safety. Here, the prevalence and characteristics of class I integrons in Escherichia coli isolates derived from food-producing animals and human patients were assessed. Of 721 E. coli isolates collected from human patients (113), pigs (298), and poultry (310), 93 (12.90%) carried the class I integrase gene (intI1). Multilocus sequence typing identified 39 sequence types from 93 intI1-postive isolates, including three novel types. Sequence analysis revealed that 59 classical class I integrons encompassed six distinct gene cassettes arrangements [dfrA17-aadA5, dfrA12-aadA2, dfrA1-aadA1, dfrA7, aac(6')-Ib, and aadA1-aac(3)-VIa]. Six insertion sequences (IS1, IS6, IS21, IS91, IS110, and IS256) and one transposon (Tn3) were harbored in proximity to the integrons. A comparison with sequences retrieved from the National Center for Biotechnology Information database demonstrated that E. coli isolates with integron sequences were detected in various food-producing animals and human hosts in environmental niches across Asia, Europe, and North America. These findings indicate the potential risk of ARG transmission between food-producing animals and humans by bacteria populations and provide useful baseline data for monitoring of ARGs. [ABSTRACT FROM AUTHOR]

Antimicrobial resistance (AMR) impacts environmental processes and poses a threat to public health even in remote glacierized areas. In this study, we aimed to (i) investigate the diversity of antibiotic resistance genes (ARGs) and integrons in culturable bacteria, and to (ii) present a snapshot of microbial resistance on a glacier and its adjacent habitats in Scandinavia. We collected samples from glacier mice, spheroidal-to-ovoidal shaped bryophyte on the glacier surface, and from a proglacial lake at Austerdalsbreen in central Norway. We found variable bacterial counts ranging from 1.6 × 103 CFU/ml in water to 4.8 × 103 CFU/ml in glacier mice, with coliforms and aminoglycoside-resistant coliforms prevalent in microalgae bloom in the proglacial lake. Class 1 integrons were more frequently observed in glaciolacustrine sediment. Integron variable regions encompassing cassettes conferring resistance to macrolides and aminoglycosides in intI1-positive strains isolated from glacier mice and associated with multidrug resistance in aminoglycoside-resistant coliforms from microalgae bloom were found. The culturable bacteria carrying variable regions of integrons were identified as Pseudomonas sp., Paenibacillus sp., Escherichia coli, Klebsiella sp., Enterobacter sp., and Citrobacter sp. Additionally, we identified other ARGs, including sul1, aadA1, ampC, blaTEM, and blaOXA, indicating the presence of multiple mechanisms of antibiotic resistance. Our findings contribute to understanding of the distribution and dissemination of antibiotic resistance via glacial bryophytes to downstream ecosystem of proglacial lake in Norway.Highlights: Glacier mice and proglacial lake are habitats for ARB and bacteria with class 1 integrons. The co-occurrence of multiple ARGs in bacteria indicates a potential for co-selection. The variable regions of integrons contain genes determining resistance to macrolides, aminoglycosides and multidrug resistance. [ABSTRACT FROM AUTHOR]

Antibiotic resistance is a significant global health concern, leading to increased morbidity, mortality, and health care costs. Integrons are genetic elements that could acquire and express gene cassettes, including those that confer antibiotic resistance. This comprehensive study focused on the distribution of integrons and their gene cassettes in clinical isolates. This study explored the structure and classification of integrons with particular emphasis on Class I, II, III, and IV integrons. It also discussed the role of integrons in antibiotic resistance. The findings of this study contribute to a better understanding of the mechanisms underlying antibiotic resistance and provide valuable insights for developing strategies to combat this public health crisis. [ABSTRACT FROM AUTHOR]

Objective: This study aimed to determine the carriage of transferable integron-associated drug resistance in Escherichia coli (E. coli) strains isolated from blood cultures. Materials and Methods: A total of 111 E. coli isolates were included in this study. Antimicrobial susceptibility testing of the isolates against 17 antibiotics was performed using an automated microbiology system. Integron-specific polymerase chain reactions (PCR) were used to detect the presence of integrons. The antibiotic resistance gene cassettes in the variable regions of integrons were analyzed by DNA sequencing. Plasmid transfer assays were performed using the broth mating method. The clonal relationships among integron-carrying strains were evaluated by pulsed-field gel electrophoresis (PFGE). Results: Resistance rates to antibiotics ranged from 0.9% to 63%. Thirty-eight strains carried gene cassettes encoding dfrA7, dfr17-aadA5, dfrV, dfrA1-aadA1, and dfrA12-aadA2. Seven strains possessed class 2 integrons with gene arrays dfrA1-sat2-aadA1 and dfrA1-sat2-aadA30. Twenty-two integron-carrying isolates harbored conjugative resistance plasmids, three of which were identified as belonging to the IncN group. Two strains with class 1 integrons, isolated from different clinics, exhibited similar patterns in the PFGE analysis. Conclusion: Approximately 50% of E. coli isolates from blood cultures at our hospital were found to carry integron-associated transferable drug resistance, suggesting their potential role in the horizontal dissemination of resistance genes. Further research is needed to understand the prevalence of E. coli strains of blood origin and the role of integrons and gene cassette arrays in the spread of resistance. [ABSTRACT FROM AUTHOR]

Integrons, which are genetic components commonly found in bacteria, possess the remarkable capacity to capture gene cassettes, incorporate them into their structure, and thereby contribute to an increase in genomic complexity and phenotypic diversity. This adaptive mechanism allows integrons to play a significant role in acquiring, expressing, and spreading antibiotic resistance genes in the modern age. To assess the current challenges posed by integrons, it is necessary to have a thorough understanding of their characteristics. This review aims to elucidate the structure and evolutionary history of integrons, highlighting how the use of antibiotics has led to the preferential selection of integrons in various environments. Additionally, it explores their current involvement in antibiotic resistance and their dissemination across diverse settings, while considering potential transmission factors and routes. This review delves into the arrangement of gene cassettes within integrons, their ability to rearrange, the mechanisms governing their expression, and the process of excision. Furthermore, this study examines the presence of clinically relevant integrons in a wide range of environmental sources, shedding light on how anthropogenic influences contribute to their propagation into the environment. [ABSTRACT FROM AUTHOR]

Cotrimoxazole, the combined formulation of sulfamethoxazole and trimethoprim, is one of the treatments of choice for several infectious diseases, particularly urinary tract infections. Both components of cotrimoxazole are synthetic antimicrobial drugs, and their combination was introduced into medical therapeutics about half a century ago. In Gram-negative bacteria, resistance to cotrimoxazole is widespread, being based on the acquisition of genes from the auxiliary genome that confer resistance to each of its antibacterial components. Starting from previous knowledge on the genotype of resistance to sulfamethoxazole in a collection of cotrimoxazole resistant uropathogenic Escherichia coli strains, this work focused on the identification of the genetic bases of the trimethoprim resistance of these same strains. Molecular techniques employed included PCR and Sanger sequencing of specific amplicons, conjugation experiments and NGS sequencing of the transferred plasmids. Mobile genetic elements conferring the trimethoprim resistance phenotype were identified and included integrons, transposons and single gene cassettes. Therefore, strains exhibited several ways to jointly resist both antibiotics, implying different levels of genetic linkage between genes conferring resistance to sulfamethoxazole (sul) and trimethoprim (dfrA). Two structures were particularly interesting because they represented a highly cohesive arrangements ensuring cotrimoxazole resistance. They both carried a single gene cassette, dfrA14 or dfrA1, integrated in two different points of a conserved cluster sul2-strA-strB, carried on transferable plasmids. The results suggest that the pressure exerted by cotrimoxazole on bacteria of our environment is still promoting the evolution toward increasingly compact gene arrangements, carried by mobile genetic elements that move them in the genome and also transfer them horizontally among bacteria. [ABSTRACT FROM AUTHOR]

Integrons, which are genetic components commonly found in bacteria, possess the remarkable capacity to capture gene cassettes, incorporate them into their structure, and thereby contribute to an increase in genomic complexity and phenotypic diversity. This adaptive mechanism allows integrons to play a significant role in acquiring, expressing, and spreading antibiotic resistance genes in the modern age. To assess the current challenges posed by integrons, it is necessary to have a thorough understanding of their characteristics. This review aims to elucidate the structure and evolutionary history of integrons, highlighting how the use of antibiotics has led to the preferential selection of integrons in various environments. Additionally, it explores their current involvement in antibiotic resistance and their dissemination across diverse settings, while considering potential transmission factors and routes. This review delves into the arrangement of gene cassettes within integrons, their ability to rearrange, the mechanisms governing their expression, and the process of excision. Furthermore, this study examines the presence of clinically relevant integrons in a wide range of environmental sources, shedding light on how anthropogenic influences contribute to their propagation into the environment.

Cotrimoxazole, the combined formulation of sulfamethoxazole and trimethoprim, is one of the treatments of choice for several infectious diseases, particularly urinary tract infections. Both components of cotrimoxazole are synthetic antimicrobial drugs, and their combination was introduced into medical therapeutics about half a century ago. In Gram-negative bacteria, resistance to cotrimoxazole is widespread, being based on the acquisition of genes from the auxiliary genome that confer resistance to each of its antibacterial components. Starting from previous knowledge on the genotype of resistance to sulfamethoxazole in a collection of cotrimoxazole resistant uropathogenic Escherichia coli strains, this work focused on the identification of the genetic bases of the trimethoprim resistance of these same strains. Molecular techniques employed included PCR and Sanger sequencing of specific amplicons, conjugation experiments and NGS sequencing of the transferred plasmids. Mobile genetic elements conferring the trimethoprim resistance phenotype were identified and included integrons, transposons and single gene cassettes. Therefore, strains exhibited several ways to jointly resist both antibiotics, implying different levels of genetic linkage between genes conferring resistance to sulfamethoxazole (sul) and trimethoprim (dfrA). Two structures were particularly interesting because they represented a highly cohesive arrangements ensuring cotrimoxazole resistance. They both carried a single gene cassette, dfrA14 or dfrA1, integrated in two different points of a conserved cluster sul2-strA-strB, carried on transferable plasmids. The results suggest that the pressure exerted by cotrimoxazole on bacteria of our environment is still promoting the evolution toward increasingly compact gene arrangements, carried by mobile genetic elements that move them in the genome and also transfer them horizontally among bacteria.

ABSTRACT: Objectives: Current research shows that the resistance of Escherichia coli (E. coli) is mainly related to integron gene cassettes. To assess the resistance of E. coli of goose origin and the carriage of its integron genes in four farms in Heilongjiang Province, antibiotic resistance phenotypes and the presence of various types of integrons were investigated. Methods: In this study, test strains were sampled and isolated from the farms, and 109 test strains were tested for drug sensitivity of 15 different antimicrobial drugs by the Kb disc diffusion method. Polymerase chain reaction was used to detect E. coli in three types of integrase genes (intI1, intI2, and intI3) and for sequencing analysis of the class I integron gene cassette. Results: Susceptibility test results show that more than 70% of tested strains exhibit resistant phenotypes to ampicillin, amoxicillin, imipenem, tetracycline, and doxycycline. The detection rate of class I integrons was 68.91%, while class II integrons and class III integrons were not detected. The detection rate of class I integrin gene cassette was 7.42%. Sequence analysis showed that strains carried different integron gene cassettes: dfrA17-aadA5, dfrA1-aadA1, dfrA27-arr-3, and aminoglycoside 3′'-nucleotidyltransferase. Conclusions: Results suggest that the detection rate of class I integrons is highly correlated with their drug resistance. Class I integrons provide a valuable guide to studying the spread and the expression of resistance genes and thus finding effective measures to prevent bacterial resistance.

Integrons are genetic components that are critically involved in bacterial evolution and antimicrobial resistance by assisting in the propagation and expression of gene cassettes. In recent decades, biochar has been introduced as a fertilizer to enhance physiochemical properties and crop yield of soil, while manure has been used as a fertilizer for centuries. The current study aimed to investigate the impact of biochar, manure, and a combination of biochar and manure on integrons, their gene cassettes, and relative antimicrobial resistance in paddy soil. Field experiments revealed class 1 (CL1) integrons were prevalent in all samples, with higher concentration and abundance in manure-treated plots than in biochar-treated ones. The gene cassette arrays in the paddy featured a broad pool of cassettes with a total of 35% novel gene cassettes. A majority of gene cassettes encoded resistance to aminoglycosides, heat shock protein, heavy metals, pilus secretory proteins, and twin-arginine translocases (Tat), TatA, TatB, and TatC. Both in combination and solo treatments, the diversity of gene cassettes was increased in the manure-enriched soil, however, biochar reduced the gene cassettes' diversity and their cassettes array. Manure considerably enhanced CL1 integrons abundance and antimicrobial resistance, whereas biochar amendments significantly reduced integrons and antimicrobial resistance. The results highlighted the differential effects of biochar and manure on integrons and its gene cassette arrays, showing increased abundance of integrons and antibiotic resistance upon manure application and decrease of the same with biochar. The use of biochar alone or in combination with manure could be a beneficial alternative to mitigate the spread of antimicrobial resistance and bacterial evolution in the environment, specifically in paddy soils. [ABSTRACT FROM AUTHOR]

Integrons are genetic components that are critically involved in bacterial evolution and antimicrobial resistance by assisting in the propagation and expression of gene cassettes. In recent decades, biochar has been introduced as a fertilizer to enhance physiochemical properties and crop yield of soil, while manure has been used as a fertilizer for centuries. The current study aimed to investigate the impact of biochar, manure, and a combination of biochar and manure on integrons, their gene cassettes, and relative antimicrobial resistance in paddy soil. Field experiments revealed class 1 (CL1) integrons were prevalent in all samples, with higher concentration and abundance in manure-treated plots than in biochar-treated ones. The gene cassette arrays in the paddy featured a broad pool of cassettes with a total of 35% novel gene cassettes. A majority of gene cassettes encoded resistance to aminoglycosides, heat shock protein, heavy metals, pilus secretory proteins, and twin-arginine translocases (Tat), TatA, TatB, and TatC. Both in combination and solo treatments, the diversity of gene cassettes was increased in the manure-enriched soil, however, biochar reduced the gene cassettes’ diversity and their cassettes array. Manure considerably enhanced CL1 integrons abundance and antimicrobial resistance, whereas biochar amendments significantly reduced integrons and antimicrobial resistance. The results highlighted the differential effects of biochar and manure on integrons and its gene cassette arrays, showing increased abundance of integrons and antibiotic resistance upon manure application and decrease of the same with biochar. The use of biochar alone or in combination with manure could be a beneficial alternative to mitigate the spread of antimicrobial resistance and bacterial evolution in the environment, specifically in paddy soils.

The pork production chain is an important reservoir of antimicrobial resistant bacteria. This study identified and characterized integrons in Salmonella isolates from a Brazilian pork production chain and associate them with their antibiotic resistance pattern. A total of 41 whole-genome sequencing data of nontyphoidal Salmonella were analyzed using PlasmidSPAdes and IntegronFinder software. Nine isolates (21.9%) had some integrons identified (complete and/or incomplete). Six complete class 1 integrons were found, with streptomycin resistance genes ( aadA1 , aadA2 ) alone or downstream of a trimethoprim resistance gene ( dfrA1 , dfrA12) , and some also containing resistance genes for sulfonamides ( sul1 , sul3 ) and chloramphenicol ( cmlA1 ). Class 2 integron was detected in only one isolate, containing dfrA1 - sat2 - aadA1 gene cassettes. Five isolates harbored CALINs-clusters attC but lacking integrases-with antimicrobial resistance genes typically found in integron structures. In all, integrons were observed among four serotypes: Derby, Bredeney, Panama, and monophasic var. Typhimurium I 4,[5],12:i:-. The association of integrons with antibiotic resistance phenotype showed that these elements were predominantly identified in multidrug resistance isolates, and six of the seven gentamicin-resistant isolates had integrons. So, surveillance of integrons in Salmonella should be performed to identify the potential for the spread of antimicrobial resistance genes among bacteria.

Carbapenem-resistant Enterobacterales (CRE) infections result in higher treatment costs and mortality rates. Integrons play important roles in emergence and spread of antibiotic resistant genes. To get a better understand on the effects of integron on CRE resistance, distribution of common carbapenemase genes and class 1 integron in clinical CRE isolates were investigated. Carbapenemase genes, including bla KPC , bla VIM , bla IMP , bla NDM , bla GES , bla VEB and bla OXA-23 , were screened in 161 CRE isolates and subtypes of these genes were confirmed through sequence analysis. Class 1 integron was screened and common promoter and gene cassette arrays were determined by sequencing. The resistant rates to clinical commonly used antibiotics between integron positive and integron negative CRE isolates were compared. Of 161 CRE isolates, the most prevalent carbapenemase gene was bla KPC-2 , which was detected in 139 isolates, including 99 Klebsiella pneumoniae. Class 1 integron was detected in 78 isolates. Twenty different gene cassettes, including two carbapenemase genes bla VEB-1 and bla IMP-4 , and nine different gene cassette arrays, including bla VEB-1 -aadB-arr-2-cmlA5-bla OXA-10 -aadA1 , aadB-catB8-bla OXA-10 -aadA1-dfrA1-aacA4 and bla IMP-4 -qacG-aacA4-catB3 , were detected. Five types of common promoters were identified. Relative weak promoter PcH1 was the dominant type. Resistant rates of CRE isolates containing class 1 integrons to ceftazidime, amikacin, trimethoprim/sulfamethoxazole and gentamicin were higher than those without class 1 integrons (P < 0.05). Class 1 integrons play important roles in the emergence and spread of CRE resistance. To the best of our knowledge, this is the first report of aadB-catB8-bla OXA-10 -aadA1-dfrA1-aacA4 and bla IMP-4 -qacG-aacA4-catB3 in the same Providencia rettgeri isolate and bla VEB-1 -aadB-arr-2-cmlA5-bla OXA-10 -aadA1 in P. rettgeri. • Twenty different gene cassettes, including two carbapenemase genes bla VEB-1 and bla IMP-4 , were detected in this study. • aadB-cat8-bla OXA-10 -aadA1-dfrA1-aacA4 and bla IMP-4 -qacG-aacA4-catB3 were reported for the first time in the same Providencia rettgeri isolate. • Bla VEB-1 -aadB-arr-2-cmlA5-bla OXA-10 -aadA1 was reported for the first time in P. rettgeri. [ABSTRACT FROM AUTHOR]

To investigate the distribution of class 1 integrons and their variable regional molecular characteristics, as well as the diversity of promoter and drug sensitivity of CR-Eco (carbapenem-resistant E. coli) strains. A total of 117 CR-Eco strains, collected between 2012.01 and 2019.12, underwent fully automated bacterial identification and sensitization using VITEK-2 Compact and supplemented by K–B assay. PCR was employed to screen for class 1 integrase genes and integron variable regions, while the promoter type and variable region gene cassette characteristics were determined by sequencing analysis. The positive rate of the class 1 integron of the CR-Eco strains was 83.70% (92/117) herein. Moreover, class 1 integrase-positive strains exhibited statistically significant resistance to aztreonam, ceftazidime, ciprofloxacin, ceftriaxone, gentamicin, meropenem, and trimethoprim-sulfamethoxazole compared to integron-negative strains (P < 0.05). Variable regions were observed in 77 of the 92 class 1 integrase-positive strains. In addition, seven gene cassettes were detected, namely dfrA17-aadA5, aadA22, dfrA12-aadA2, dfrA12, dfrA17, dfrA27 and aadA. Finally, five types of class 1 integron variable region promoters were identified in those 77 strains, including PcW, PcH1, PcW TGN-10 , PcH1 TGN-10 , and P2, which were detected in 48, 18, 8, 2, and 1 strains, respectively. The primary integrator variable region gene cassettes of this class were dfrA and aadA. The integron-positive strains displayed simultaneous high resistance to multiple antimicrobial drugs. The integrator variable region promoters of the CR-Eco strains are primarily weak and can potentially form and spread drug resistance. • A total of 117 CR-Eco strains, collected between 2012.01 and 2019.12 • The promoter type and variable region gene cassette characteristics were determined by sequencing analysis of CR-Eco strains. • Analysis the distribution of class 1 integrons and their variable regional molecular characteristics and drug sensitivity of CR-Eco strains. [ABSTRACT FROM AUTHOR]