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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., Competing Interests: Declarations. Ethics approval and consent to participate: All animal experiments were conducted in accordance with the protocols of the Institutional Animal Care and Use Committee of Hangzhou Hibio Technology Co.,Ltd. (approval no. HB2407026). Competing interests: The authors declare no competing interests. Declaration of competing interest: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2025. The Author(s).)

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., (Copyright © 2022 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Harmonious ecological environment is a major concern with rising feeding and consumption of ducks, as these waterfowl birds can promote the spread of antibiotic resistant genes (ARGs). Therefore, this study was conducted to know diversity of antimicrobial resistance (AMR), integrons, and mobile genetic elements (MGEs) in Escherichia coli (E. coli) isolated from intestinal contents or pericardial effusion of diseased ducks from 2018 to 2020 in Sichuan, China. The AMR phenotype was determined via disk diffusion test in 165 E. coli isolates. Further, the integrase genes of integron (intI1, intI2 and intI3 genes), gene cassettes (GCs) and MGEs were screened by PCR and sequencing. The results indicated 100% isolates were resistant to at least one antibiotic and 98.8% were multidrug-resistant strains. Highest AMR phenotype was recorded to rifampin (97.0%) followed by ampicillin (95.8%), chloramphenicol (89.7%), trimethoprim-sulfamethoxazole (84.2%), ciprofloxacin (83.0%), cefotaxime (80.0%), streptomycin (75.8%), doxycycline (49.7%), amikacin (10.3%), amoxicillin/clavulanic acid (3.6%), polymyxin B (1.2%) and ertapenem (0.6%). Further, class 1 and 2 integrons were found in 87.3% and 17.6% isolates, respectively. All isolates were negative for intI3 gene. The variable region of class 1 and 2 integrons contained total 13 different GCs, including arr-3+dfrA27, dfrA1+aadA1, dfrA17+aadA5, dfrA12, dfrA1+sat2+aadA1, dfrA12+aadA2, dfrA5, aadA2+ere(A)+dfrA32, aac(6')-Ib-cr, aadA22, aadA5, dfrA17, and dfrA27. Moreover, 13 MGEs in 69 different combinations were observed with predominance of IS26 followed by tnpA/Tn21, trbC, ISEcp1, merA, ISAba1, tnsA, tnsB, tnsC, IS1133, tnsD, ISCR3/14, and tnsE. Thus, the monitoring of integrons, MGEs and ARGs is important to understand the complex mechanism of AMR, which might help to introduce interventions for prevention and control of AMR in duck farms in China., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

This study was conducted to determine the prevalence of integrons and associated gene cassettes in Escherichia coli (E. coli) isolates from waterfowls in Hainan, China. The antimicrobial resistance profile of the isolates was examined by using disc diffusion test. In addition, PCR, RFLP, plasmid replicon typing and DNA sequencing analyses were used for the characterization of integrase genes (class 1, 2 and 3) and associated gene cassettes. Approximatively, 90% of the isolates were positive for the integrase genes by PCR. Specifically, class 1 and class 2 integrons were found in 252 (81%) and 7 (2.3%) strains, respectively. While 21 (6.7%) isolates were positive for both class 1 and class 2 integrons. However, none of the isolate was positive for the class 3 integrons. In addition, 5 various cassette arrays, dfrA1-orfC, aadA2, aadA1, dfrA1-aadA1, and dfrA1-orfC- aadA1, were found within the variable regions (VRs) of class 1 integron isolates. While only single cassette array, dfrA1-sat2- aadA1, was identified within VRs of class 2 integron isolates. We identified incF plasmid as the most common plasmid type, which was detected in 81 of 243 VRs containing isolates. This study is the first report showing the baseline characteristics of integrons in E. coli isolates from waterfowls in Hainan, China. Our results provide evidence of the waterfowl birds as a reservoir of class 1 and class 2 integrons carrying antibiotic resistance gene cassettes. Therefore, strict preventive measures should be taken to avoid the spread of mobile genetic resistance elements in waterfowls in China., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Whole-genome sequencing of trimethoprim-resistant Escherichia coli strains MF2165 and PF9285 from healthy Swiss fattening calves revealed a so far uncharacterized dihydrofolate reductase gene, dfrA35 Functionality and association with trimethoprim resistance were demonstrated by cloning and expressing dfrA35 in E. coli The DfrA35 protein showed the closest amino acid identity (49.4%) to DfrA20 from Pasteurella multocida and to the Dfr determinants DfrG (41.2%), DfrD (40.8%), and DfrK (40.0%) found in Gram-positive bacteria. The dfrA35 gene was integrated within a florfenicol/chloramphenicol-sulfonamide resistance IS CR2 element ( floR -IS CR2 - dfrA35 - sul2 ) next to a Tn 21 -like transposon that contained genes with resistance to sulfonamides ( sul1 ), streptomycin ( aadA1 ), gentamicin/tobramycin/kanamycin ( aadB ), and quaternary ammonium compounds ( qacE Δ 1 ). A search of GenBank databases revealed that dfrA35 was present in 26 other E. coli strains from different origins as well as in Acinetobacter IMPORTANCE The presence of dfrA35 associated with IS CR2 in Escherichia coli from animals, as well as its presence in other E. coli strains from different sources and countries and in Acinetobacter , highlights the global spread of this gene and its potential for further dissemination. The genetic link of IS CR2 - dfrA35 with other antibiotic and disinfectant resistance genes showed that multidrug-resistant E. coli may be selected and maintained by the use of either one of several antimicrobials., (Copyright © 2019 Wüthrich et al.)

We investigated the occurrence of integrons in antibiotic-resistant Escherichia coli strains isolated from free-ranging food animals, including yaks, piglets, and chickens, in China, and characterized the gene cassettes harbored within the integrons. We examined 432 E. coli strains that exhibited resistance to at least one class of antibiotics. Integrase genes and associated gene cassettes were characterized by polymerase chain reaction (PCR) analysis, restriction fragment-length polymorphism, DNA sequencing, conjugation experiments, and plasmid analysis. Twenty-nine (6.7%) integrons were amplified from the 432 antimicrobial-resistant (AMR) isolates evaluated. Specifically, class 1 and 2 integrons were detected in 26 (6%) and 3 (0.7%) strains, respectively. Meanwhile, 6 different gene cassettes, dfrA1, dfr12, aadA1, aadA2, sat1, and orfF, were detected within 6 variable regions (VRs), of which the dfrA1 + aadA1 array was the most common, identified in 12 of 26 class 1 integrons (46.1%). Meanwhile, only one class 2 integron contained a cassette, and the remaining two contained undetermined VRs. Finally, a conjugation assay confirmed the transfer of 4 different types of class 1 integrons into recipient strains, with plasmid sizes ranging from 20 to 30 kb. This is the first report examining the baseline AMR characteristics of E. coli within an extensive farming system of livestock animals in China. Given that integrons were detected in >6% of resistant E. coli strains, precautionary measures are required to prevent the spread of mobile genetic resistance determinants in food animals and monitor their emergence., (© 2017 Institute of Food Technologists®.)

By searching the Integrall integron and GenBank databases, a novel open reading frame (ORF) of 51 nucleotides (nts) (ORF-17) overlapping the previously described ORF-11 was identified within the attI1 site in virtually all class 1 integrons. Using a set of isogenic plasmid constructs carrying a single gene cassette ( bla GES-1 ) and possessing a canonical translation initiation region, we found that ORF-17 contributes to GES-1 expression., (Copyright © 2017 American Society for Microbiology.)

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]

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]

The emergence of multidrug (MDR) isolates of Escherichia coli has made the treatment of urinary tract infections (UTI) very challenging. Integrons are considered to be one of the most important mechanisms in the dissemination of resistance genes. In the current study, we sought to investigate the antibiotic resistance patterns, class 1–3 integrons and corresponding gene cassettes in urinary isolates of E. coli in the southwest of Iran. A total of 144 E. coli isolates were collected from the patients with UTIs. Antibiotic susceptibility test conducted by the disc diffusion method using 12 different antibiotics. The polymerase chain reaction (PCR) was used for the detection of intl1, intI2, and intI3 genes. To analyze the gene cassettes, variable regions of class 1 integron were amplified by PCR and subjected to sequencing. The highest rates of resistance were exhibited to amoxicillin/clavulanic (73.6%), trimethoprim-sulfamethoxazole (63.9%) and tetracycline (63.2%). Totally, intI1 and intI2 genes were identified in 62.5 and 9% of isolates. One-hundred and nine (75.7%) E. coli isolates were multidrug resistance (MDR), among which 78% harbored intI1 gene. Also, all of the intI2 positive E. coli isolates were MDR. Ten different gene cassette arrays were found in intl1 positive E. coli including dfrA5, dfrA25, dfrA7, aacA4, aadA1, aadB-catB3, dfrA17-aadA5, dfrA12-orfF-aadA2, aadA1-blaOXA-30, and dfrA5-catB3-aacA4. The dfrA17-aadA5 was the most prominent gene cassette array among E. coli isolates. Characterization of resistance gene cassettes located in integrons in this study showed a high frequency of dfrA and aad genes which confer resistance to trimethoprim and aminoglycosides. The obtained result from this study could be useful in planning to prevent the rising rate of antibiotic resistance. [ABSTRACT FROM AUTHOR]

The objective was to investigate the multidrug resistance and presence of class 1 and 2 integrons in 300 Escherichia coli isolates obtained from 20 broiler farms during three rearing periods (one-day-old chicks, thirty-day-old chickens, and one day before slaughter) in Fars, South Iran. Results showed that 81.00%, 82.00%, and 85.00% of isolates were multidrugresistant on the first day, thirty-day-old chickens, and one day before slaughter, respectively. Multidrug-resistant E. coli isolates were further examined for the presence of class 1 and 2 integrons using PCR assay. The existence of class 1 integron-integrase gene (intI1) was confirmed in 68.40%, 72.70%, and 60.90% of multidrug-resistant isolates from stage 1, stage 2, and stage 3 of the rearing period, respectively. The frequency of class 2 integron-integrase gene (intI2) during the first to the third stage of sampling was 2.60%, 25.50%, and 30.40%. Also, sequence analysis of the cassette arrays within class 1 integron revealed the presence of the genes associated with resistance for trimethoprim (dfrA), streptomycin (aadA), erythromycin (ereA), and orfF genes. The results revealed that percentages of antimicrobial resistance in E. coli isolates were significantly higher in the middle and end stages of the rearing period. In conclusion, widespread dissemination of class 1 integrons in all three stages and rising trends of class 2 integrons existence in E. coli isolates during the rearing period of broiler chickens could exacerbate the spread of resistance factors among bacteria in the poultry industry. Future research is needed to clarify its implication for human health. [ABSTRACT FROM AUTHOR]

Our study was conducted to investigate the antibiotic susceptibility profiles, integrons and their associated gene cassettes (GCs), and insertion sequence common regions of Escherichia coli isolates from Penaeus vannamei collected at a large-scale freshwater shrimp farm in Zhejiang Province, People’s Republic of China. A total of 182 E. coli isolates were identified from 200 samples. With the exception of imipenem, isolates were most commonly resistant to β-lactams, followed by tetracylines and sulfonamides. Fifty-two (28.6%) E. coli isolates were classified as multidrug resistant, and the patterns were highly diverse, with 29 types represented. The multiple-antibiotic resistance indices of the isolates were 0.17 to 0.56; 9.3% (17) of the 182 isolates were positive for class 1 integrons, 0.5% (1 isolate) was positive for class 2 integrons, and an insertion sequence common region 1 element was found upstream of the intI1 (integrase) gene in one of the intI1-positive isolates. Four GC arrays were detected in class 1 integrons, and one GC array was detected in class 2 integrons. Although the overall prevalence of antimicrobial-resistant bacteria in P. vannamei was lower than that previously reported for poultry and livestock farms in China, concerns about the inappropriate use of antibiotics and the transmission of antimicrobial-resistant bacteria in aquaculture were raised. Alternative approaches to reducing or replacing the use of antibiotics should be further studied. [ABSTRACT FROM AUTHOR]

Abstract The pork production chain and raw pork products are among the most important reservoirs of antimicrobial-resistant microorganisms. This study investigated the antimicrobial resistance profiles and integrons and their associated gene cassettes of Escherichia coli isolated from a large-scale centralized swine slaughterhouse in Zhejiang, China and its downstream markets. A total of 300 E. coli isolates were identified from 720 samples. No E. coli isolates were detected on the slaughtering line or at downstream supermarkets. Of the 300 E. coli isolates collected from lairages and downstream open markets, 242 (80.67%) were classified as multi-drug resistant (MDR). In addition, the prevalence of multi-drug resistance was significantly different (p < 0.05) and antimicrobial resistance profiles varied among the different sampling points. Furthermore, of 300 E. coli strains, 76 (25.33%) were positive for class 1 integrons and nine (3.00%) were positive for class 2 integrons. Three different gene cassettes were detected in class 1 integrons and one gene cassette was detected in class 2 integrons. Our study demonstrates that E. coli isolates from lairages and open markets are frequently MDR, and suggests that precautionary measures and hygienic environments are necessary to prevent the spread of antimicrobial-resistant microorganisms and their mobile genetic elements through the food chain. Highlights • No E. coli isolate was detected on the slaughtering line or at supermarkets. • E. coli from lairages and open markets were highly multi-drug resistant. • Multi-drug resistance rates of E. coli differed significantly among sampling sites. • Antimicrobial resistance profiles of E. coli varied between sampling sites. • Class 1 and 2 integrons and various gene cassettes were identified. [ABSTRACT FROM AUTHOR]

Integrons are genetic platforms able to excise, integrate and express antibiotic resistance gene cassettes (GCs). Here we investigated the complete genetic organisation, genetic environment, location and conjugative transferability of a collection of class 2 integrons carried by Escherichia coli strains from different sources (poultry/pork meat, animals and humans). PCR cartography was conducted to determine the genetic arrangement of the integrons, their physical linkage to Tn 7 and chromosomal insertion at the attTn7 site. Clonal relatedness of specific isolates was determined by MLST and DO-PCR. Transferability of class 2 integrons was tested by conjugation. The resulting transconjugants were characterised by antimicrobial resistance genotyping, S1-PFGE and replicon typing. Although a limited diversity of GCs was shown, a high percentage of novel structures was identified owing to the integration of insertion sequence (IS) elements at different sites (IS 3 /IS 4 /IS 5 /IS 21 families). Insertion of IS 10 in the attI2 site of a class 2 integron, between Pc2B and Pc2C promoters, was likely mediated by a site-specific transposition event. Chromosomal insertion of integrons at attTn7 was confirmed in 80% of the isolates. Conjugation experiments demonstrated that 29% of class 2 integrons could be mobilised to E. coli CHS26, demonstrating that they can be located in conjugative/mobilisable elements at a low frequency. Reported structures evidence how class 2 integrons have evolved by the activity of integron integrases and the invasion of ISs. Since most of them are chromosomally located, dispersion is predominantly vertical, although conjugation events also contribute to the spread of class 2 integrons among bacterial communities. [ABSTRACT FROM AUTHOR]

In spite of the role of integrons as the main contributor to multidrug resistance worldwide, their prevalence in Egypt is still underestimated. In this work, we announce the emergence of class 2 and 3 integrons among Enterobacteriacae isolates from Mansoura University Hospitals. Ninety-three clinical isolates were obtained from different clinical sources, among which 70% of E. coli , 94.8% of K. pneumonia e and 85.7% of Enterobacter spp. were assigned to be multidrug resistant (MDR). Subsequently, the occurrence of class 1–3 integrons was confirmed by multiplex PCR. Class 1 integron was the most predominant being harbored by 42.8%, 90% and 25% of MDR E. coli , K. pneumonia e and Enterobacter spp. isolates, respectively. This was followed by class 2 and 3 integrons which were, for the first time, reported in these hospitals. Also, coexistence of integrons 1and 2 was revealed in 36.9% of integron positive isolates. A significant association was noticed only between resistance to gentamicin and integron prevalence among MDR E. coli isolates (P = 0.02). In conclusion, this work represents the first report for detection of class 2 and 3 integrons, beside the previously detected class 1 integrons. This highlights the high incidence of integrons among MDR Enterobacteriacae isolates which indicates the selective pressure of antibiotics in these hospitals. Moreover, this study confirms the possibility of the use of integrons as markers for MDR identification. [ABSTRACT FROM AUTHOR]

The whole genome sequencing of extensively drug-resistant Shewanella xiamenensis T17 isolated from hospital effluents in Algeria revealed the presence of a novel 268.4 kb plasmid designated pSx1, which carries several antibiotic-resistance genes in the novel Tn 1696 derivative (Tn 6297), in addition to the chromosomal blaOXA-48-like gene ( blaOXA-416). The presence of the plasmid was confirmed by nuclease S1-PFGE analysis and transformation by electroporation into Escherichia coli DH10B. Tn 6297 contains an In27 class 1 integron harboring the dfrA12-orfF-aadA2 array, msr(E) and mph(E) associated with IS 26; a new efflux pump multidrug resistance composite transposon delimited by two IS Ec29s; Tn-tet harboring tetR and tetA(C); a class 1 integron with the qacG gene cassette ; qnrVC6 and dfrA23 associated with IS CR1; and a complex class 1 integron In4-like containing aacC1, aadA1, blaVEB-16, catA2, sul1Δ, cmlA9, tetR, tetA(G), aac(6′)-II, and blaPSE-1. Its mer operon carries merB, but lacks merC, in contrast to Tn 1696 and Tn 21. This study represents the first characterization of a multidrug-resistant transposon and multidrug resistance plasmid in Shewanella and is the first report of blaOXA-416 in Algeria, providing evidence that Shewanella spp. could be an important reservoir and vehicle for drug resistance genes. [ABSTRACT FROM AUTHOR]

Integrons by means of horizontal gene transfer carry multidrug resistance genes (MDR) among bacteria, including E. coli. The aim of this study was to determine the antibiotic resistance profiles and the genes associated with them, to gain insights in the distribution of phylogroups, prevalence, and characterization of class 1, 2 and 3 integrons among Enteropathogenic E. coli (EPEC) isolates, from children upto 5 years of age from Delhi and National Capital Region (NCR), India. A total of 120 E. coli isolates, including 80 from diarrheagenic E. coli (cases) and 40 from healthy isolates (controls) were recruited in this study. After isolation of E. coli, screening for EPEC was done by conventional multiplex PCR. Antibiotic suseptibility test was performed using disk diffusionmethod and further confirmed by minimum inhibitory concentration (MICs) by E-test. The presence and characterization of integrons and antimicrobial resistance genes were performed by PCR and DNA sequencing. Phylogeny determination was carried out by quadruplex PCR. EPEC strains were found in 64 of the 80 diarrheagenic cases, out of which 38 were MDR. In the 40 healthy controls, 23 were found to be EPEC strain, out of which only 2 were MDR. Amongst 80 diarrheagenic cases, class 1 integron were observed in 43 isolates, class 2 integron in 12 isolates and 9 isolates were found with co-existence of both. Similarly, in healthy controls; class 1 integron in 9 and class 2 integron in 7 isolates were observed with co-existence in 3 isolates. None of the isolates included class 3 integron. The dfr was the most commonly identified gene cassette within the integron-positive isolates. Phylogenetic studies showed considerable representation of phylogroup B2 in both diarrheagenic cases and healthy controls. This study reiterates the importance of class 1 integron predominantly for acquisition of antibiotic resistance genes among EPEC isolates. Furthermore, it also ascertains the possible association betweenmultidrug resistance and presence of integrons. Approximately 91% of isolates were easily assigned to their respective phylogroups. Assessment of the relationship between antibiotic resistance and dominant phylogroups detected was also attempted. This study also highlights the increased burden of antimicrobial resistance in healthy controls. [ABSTRACT FROM AUTHOR]

Background: The human and animal intestinal tract harbors a complex community of microbes which enables bacteria to inherit antibiotic resistance genes. 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. Methods: A total of 200 E. coli isolates from human, chicken, cattle, and sheep were isolated followed by phenotypic antibiotic susceptibility testing and detection of class I and II integrons gene cassettes arrays. The clonal relationship of the isolates were analyzed by (GTG)5-PCR. Results: Of 200 isolates, 136 isolates were multi drug resistance (MDR) including 47, 40, 31 and 18 isolates from chicken, human, cattle and sheep, respectively. Class I integron was detected in 50, 38, 6 and 16%, while class II was detected in 26, 8, 0 and 4% of chicken, human, cattle and sheep isolates, respectively. Variable regions were amplified and sequenced. Cassette arrays in class I integrons were: dfrA1, dfrA5, dfrA7, dfrA12, aadA1, dfrA17 aadA1, aadA22, aadB-aadA2 and dfrA12-orfF-aadA2, and for class II, dfrA1-sat-aadA1, and sat-sat1-aadA1 were detected. Six class I and three class II positive strains did not produce any amplicons for variable region. Integron-positive isolates showed higher rate of resistance to streptomycin and trimethoprim-sulphamethoxazole, especially in chicken isolates which were fed antibiotics. Low similarity and great genetic diversity of class I and II integrons carrying isolates indicated no clonal relation. Conclusions: Integrons encoding for antibiotic resistance are significantly present among non-pathogenic commensal E. coli, especially from the hosts medicated by antibiotics. Uncontrolled use of antibiotics will increase the numbers of multiple drug resistant isolates and integrons prevalence. [ABSTRACT FROM AUTHOR]

Discharge of untreated sewage into Antarctic environments presents a risk of introducing non-native microorganisms, but until now, adverse consequences have not been conclusively identified. Here we show that sewage disposal introduces human derived Escherichia coli carrying mobile genetic elements and virulence traits with the potential to affect the diversity and evolution of native Antarctic microbial communities. We compared E . coli recovered from environmental and animal sources in Antarctica to a reference collection of E. coli from humans and non-Antarctic animals. The distribution of phylogenetic groups and frequency of 11 virulence factors amongst the Antarctic isolates were characteristic of E. coli strains more commonly associated with humans. The rapidly emerging E. coli ST131 and ST95 clones were found amongst the Antarctic isolates, and ST95 was the predominant E. coli recovered from Weddell seals. Class 1 integrons were found in 15% of the Antarctic E. coli with 4 of 5 identified gene cassette arrays containing antibiotic resistance genes matching those common in clinical contexts. Disposing untreated sewage into the Antarctic environment does disseminate non-native microorganisms, but the extent of this impact and implications for Antarctic ecosystem health are, as yet, poorly understood. [ABSTRACT FROM AUTHOR]

Integrons are considered to play a significant role in the evolution and spread of antimicrobial resistance genes. 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 integron-associated integrase ( intI) genes and gene cassettes. Conjugal transfer and Southern hybridization were performed to determine the genetic localization of class 1 integrons. One hundred ninety-two (96%) isolates were resistant to one or more antimicrobial agents. Antimicrobial resistance among DEC isolates was higher compared with the UPEC. Integrons were highly prevalent in both pathotypes (92.5%). Comparison of integrons among UPEC and DEC showed that DEC isolates harbored integrases (94% for intI1, 8% for intI2) with a slightly higher frequency than in UPEC isolates (87% for intI1, 7% for intI2) ( p>0.05). Dihydrofolate reductase ( dfrA) and aminoglycoside adenyl transferase ( aad) gene cassettes were found most frequently in intI1-positive isolates. All isolates carried their class 1 integrons on conjugative plasmids. These results indicate that class 1 integrons are widespread among E. coli isolates. Therefore, appropriate surveillance and control measures are essential to prevent the further spread of integron-producing isolates. [ABSTRACT FROM AUTHOR]

A consortium comprised of an engineered Escherichia coli DH5α and a natural pentachlorophenol (PCP) degrader, Sphingobium chlorophenolicum ATCC 39723, was assembled for degradation of hexachlorobenzene (HCB), a persistent organic pollutant. The engineered E. coli strain, harbouring a gene cassette ( camA camB camC) that encodes the F87W/Y96F/L244A/V247L mutant of cytochrome P-450cam (CYP101), oxidised HCB to PCP. The resulting PCP was then further completely degraded by ATCC 39723. The results showed that almost 40 % of 4 μM HCB was degraded by the consortium at a rate of 0.033 nmol/mg (dry weight)/h over 24 h, accompanied by transient accumulation and immediate consumption of the intermediate PCP, detected by gas chromatography. In contrast, in the consortium comprised of Pseudomonas putida PaW340 harbouring camA camB camC and ATCC 39723, PCP accumulated in PaW340 cells but could not be further degraded, which may be due to a permeability barrier of Pseudomonas PaW340 for PCP transportation. The strategy of bacterial co-culture may provide an alternative approach for the bioremediation of HCB contamination. [ABSTRACT FROM AUTHOR]

In this study, antimicrobial-resistance patterns were analyzed in Escherichia coli isolates from raw (RW) and treated wastewater (TW) of two wastewater treatment plants (WWTPs), their marine outfalls (MOut), and mouth of the Vistula River (VR). Susceptibility of E. coli was tested against different classes of antibiotics. Isolates resistant to at least one antimicrobial agent were PCR tested for the presence of integrons. Ampicillin-resistant E. coli were the most frequent, followed by amoxicillin/clavulanate (up to 32 %), trimethoprim/sulfamethoxazole (up to 20 %), and fluoroquinolone (up to 15 %)-resistant isolates. Presence of class 1 and 2 integrons was detected among tested E. coli isolates with rate of 32.06 % ( n = 84) and 3.05 % ( n = 8), respectively. The presence of integrons was associated with increased frequency of resistance to fluoroquinolones, trimethoprim/sulfamethoxazole, amoxicillin/clavulanate, piperacillin/tazobactam, and presence of multidrug-resistance phenotype. Variable regions were detected in 48 class 1 and 5 class 2 integron-positive isolates. Nine different gene cassette arrays were confirmed among sequenced variable regions, with predominance of dfrA1-aadA1, dfrA17-aadA5, and aadA1 arrays. These findings illustrate the importance of WWTPs in spreading of resistance genes in the environment and the need for inclusion of at least monitoring efforts in the regular WWTP processes. [ABSTRACT FROM AUTHOR]

The aim of the study was to determine the occurrence of integron-bearing Gram-negative bacteria in the water of four lakes located in Wielkopolski National Park, Poland. Altogether, 17 isolates harbouring class 1 or class 2 integrons were found. The integron-bearing bacteria were identified as Escherichia coli, Klebsiella pneumoniae, Pasteurella multocida and Aeromonas hydrophila. The variable regions of the class 1 integrons contained aadA1 and dfrA1-aadA1 gene cassettes, whereas class 2 integrons carried dfrA1-sat2-aadA1 gene cassette array. The isolates were resistant to 3-20 antimicrobials. One of them produced SHV-type extended-spectrum β-lactamase. Significance and Impact of the Study Integrons play a major role in the spread of antibiotic resistance among bacteria. They are frequently found in clinical bacterial strains, but are also detected in environmental isolates in sites affected by anthropogenic pressure. Little is known, however, about the presence and characteristics of integrons in bacteria living in water environments in areas of nature preservation. To the best of our knowledge, this is the first study focused on detection and characterization of integrons in bacteria living in water ecosystems in a national park. [ABSTRACT FROM AUTHOR]

This study is aimed at determining the antimicrobial resistance (AMR) and the presence of class 1 and 2 integrons in 48 avian pathogenicEscherichia coli(APEC) strains isolated from meat turkeys during three sequential production cycles. Thirty avian faecalE. coli(AFEC) strains from the first cycle were also analysed. Strains were tested for AMR against 25 antimicrobials by disk diffusion test and were screened for the presence of integrons and associated gene cassettes by polymerase chain reaction followed by sequencing. Genetic relatedness of isolates was established by pulsed-field gel electrophoresis. High levels of resistance were detected to tetracyclines, penicillins and sulphonamides in APEC and AFEC. Resistance to aminoglycosides, fluoroquinolones, cephalosporins and phenicols was variable, based on the antimicrobial drug and the isolate (APEC vs. AFEC). Full susceptibility to colistin was detected. Multidrug resistance of up to seven antimicrobial classes was exhibited by APEC (93.8%) and AFEC (100%). Nearly 44% of strains tested positive for class 1 and/or class 2 integrons containing thedfrA,aadAandsat2genes, alone or in combination, coding for streptomycin/spectinomycin, trimethoprim and streptothricin resistance, respectively. TheestXandorfF genes of unknown function were also detected. A significant association was found between the presence of integrons and the resistance to aminoglycosides and potentiated sulphonamides. The results of this study showed that AMR, multidrug resistance and class 1 and 2 integrons are widespread among pathogenic and commensalE. colifrom Italian turkeys. More attention should be addressed to limit the use of antimicrobials in turkeys and the AMR of turkeyE. coli. [ABSTRACT FROM PUBLISHER]

Background and Objectives: The therapeutic options for diseases caused by Escherichia coli are limited. In this study we investigated the presence of virulence factors among Enteropathogenic Escherichia coli (EPEC) strains and their antibiotic resistance patterns. The isolates were also checked for the presence of class 1 integrons and gene cassettes. Materials and Methods: This study included 70 EPEC strains isolated from children. Antimicrobial resistance patterns were determined using diffusion methods. The broth microdilution methods was used to determine the minimum inhibitory concentration. PCR was used to detect eaeA, bfpA genes. The 5' and 3' conserved sequences (CSs) of class 1 integrons and intI gene were amplified to investigate the presence of integrons and gene cassettes. Results: Antimicrobial susceptibility testing showed that 4 (5.7%), 3 (4.2%), and 2 (2.8 %) isolates were resistant to ampicillin, trimethoprim-sulfamethoxazole, and ceftazidime, respectively. Resistance rates to ciprofloxacin and aztreonam were 1.4%. Thirteen (18.5%) isolates showed resistance to tetracycline, and 4 (5.7%) were kanamycin resistant. Class I integron detected in 22 (31.4%) isolates. All the gene cassettes found in class I integrons corresponded to different variants of dfr and aadA genes. Conclusion: Prevalence of class I integrons in EPEC strains was high. Presence of aadA and dfr gene cassettes in integrons represents high distribution of resistance determinants in EPEC strains. [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]

Objective: The aim of study was to investigate the distribution of the integrons in Escherichia coli (E. coli) isolates, and analyze the possible relationship between the antimicrobial resistance profiles and the integrons. Methods: The antimicrobial profiles of 376 E. coli strains were analysed by disk diffusion test. The integron genes and variable regions were detected by PCR. Some amplicons were sequenced to determine the gene cassettes style. Results: Of 376 isolates, 223 isolates (59.3%) were confirmed as ESBL-EC. Comparison to ESBL-negative E. coli, the high rates of resistance to the third and fourth generation of cephalosporins, penicillins and amikacin were found in ESBL-EC. Only class 1 was integron detected in the isolates, and the prevalence of it was 66.5%. It was commonly found in ESBL-EC (77.6%, 173/223), which was higher than that of ESBLnegative E. coli (50.3%, 77/153) (p < 0.001). Six different genes cassettes were detected in this study and were classified into three groups: dfr17-aadA5, dfrA12-aadA2 and aacA4-CmlA1. Additionally, more than one gene array harboured in 13.9% isolates of ESBL-EC, while in 9.1% isolates of ESBL-negative E.coli. Conclusion: The high incidence of ESBL-EC with resistance to multiple antibiotics were detected in the isolates from Blood stream infection (BSI). More resistant gene cassettes in ESBL-EC may partially underlie the high resistance to amikacin, while no relation exists between the high incidence of ESBL-EC and classes 1~ 3 integrons in this region. [ABSTRACT FROM AUTHOR]

Class 1 integrons play important roles in the emergence and horizontal transfer of antibiotic resistance genes among bacteria. The gene cassette promoter variants Pc or Pc-P2 of class 1 integrons not only drive the transcription of downstream gene cassettes, they also correlate with the excision and integration efficiency of the capture exogenous gene cassettes. In this study, the diversity of Pc or Pc-P2 variants of class 1 integrons and their association with antibiotic resistance phenotypes were analyzed in 132 uropathogenic Escherichia coli strains. Class 1 integrons were detected in 95 (72 %) strains. Sixteen different gene cassettes, 11 different gene cassette arrays and six different Pc or Pc-P2 variants were detected. The most prevalent gene cassettes were those that conferred resistance to trimethoprim, aminoglycosides, and chloramphenicol. The most prevalent promoter was PcH1, a relatively weak promoter. Certain gene cassette arrays or gene cassettes were mainly associated with the same Pc or Pc-P2 in different strains. Strains harboring class 1 integrons with relatively strong promoters had higher resistance rates to, or higher MIC for, amikacin, chloramphenicol and tobramycin than those with relatively weak promoters. To the best of our knowledge, this is the first report of the diversity of class 1 integron Pc or Pc-P2 variants in uropathogenic E. coli strains. [ABSTRACT FROM AUTHOR]

This study aimed to detect integrons, β-lactamase genes and to characterize sulfonamide resistant E. coli isolates recovered from poultry. All the isolates (n=38) were investigated for the presence of integrons, Sul1, Sul2, Sul3 genes by PCR. Class 1 and class 2 integron were present in 79 and 16%, respectively. Additional resistance gene cassette embedded in class 1 and 2 integrons was aadA1, aadA5, dfrA17 and aadA22, dfrA, respectively. Sul1 and Sul2 genes were detected in 42.1 and 60.5% isolates, respectively. Both the Sul1 and Sul2 were present in 23% isolates. However, Sul3 gene was not present. Co-existence of Sul1 and Sul2 with class 1 integrons was found in 28.9 and 60.5% of class 1 integron positive isolates, respectively. Whereas, a less percentage of isolates showed a low level of resistance to ß-lactams and no blaCTX-M, blaSHV and blaTEM was found. The MIC results showed resistance to sulfadiazine and sulfamethoxazole-trimethoprim in 88 and 84% isolates, resistance to penicillin, ampicillin, amoxicillin was 52, 52 and 44%, respectively. Chloramphenicol, florfenicol, tetracycline and gentamycin resistance was found in 51, 5, 42 and 67% isolates, respectively. This study revealed high frequency of class 1 integrons, Sul genes among poultry E. coli isolates, therefore further spread of Sul genes and integrons is predictable. [ABSTRACT FROM AUTHOR]

Abstract: The aims of this study were (a) to perform a time-related quantitative analysis of relative integron frequencies in intestinal Escherichia coli isolates from food animals (pigs and chickens) and (b) to analyse putative relationships between integrons, antimicrobial resistance and phylogenetic groups. The E. coli collection of the Spanish Veterinary Antimicrobial Resistance Surveillance Network was used to extract 393 intestinal isolates from healthy pigs and chickens belonging to the oldest (1998/99) and the latest (2006) available surveillance programs, and their quantitative antimicrobial resistance data. PCR and sequencing were used for detection and characterisation of integrons. Integron overall relative frequencies ranged between 80% and 49%, being higher in pig than in chicken E. coli isolates in both periods. Time-related analysis showed no variations when considering overall frequencies (80% versus 75% in pig E. coli isolates and 49% versus 51% in E. coli chicken isolates). Apart from the 3′-integron sul gene, six different antimicrobial-related gene cassettes (with different variants) were detected in the sequenced integron variable regions: aadA, dfrA, and sat in classes 1 and 2, and cmlA, linF and aadB only in class 1. Multiresistance profiles showed a high association between antimicrobial resistance and integron presence for those antimicrobials corresponding to the antimicrobial-related gene cassettes detected (streptomycin, trimethoprim, chloramphenicol, plus sulphonamides). However, the presence of integrons was also associated with resistance to amoxicillin and tetracycline, two antimicrobials that are widely used in animals but not linked to these genetic elements. [Copyright &y& Elsevier]

Objectives A previous study identified an association between high MICs of quaternary ammonium compounds (QACs) and antibiotic resistance. The current aim was to investigate the genetic background of this association. Methods Of 153 Escherichia coli clinical strains, seven were selected for their low or high MICs of antibiotics and/or QACs. Integron resistance gene contents were identified by sequencing after PCR amplification. The genes encoding the efflux pump AcrA/TolC and its regulatory regions marA, marO, marR, soxS and rob were sequenced. The gene expression of acrA, tolC, marA, marOR, soxS and rob was assessed by quantitative real-time PCR. MICs in the presence and absence of the efflux pump inhibitor phenyl-arginine-β-naphthylamide (PAβN) were compared. Results Of the seven strains, five were resistant to amoxicillin, amoxicillin/clavulanic acid and/or co-trimoxazole (trimethoprim/sulfamethoxazole) and/or had high MICs of ciprofloxacin and QACs. Four of the five harboured a class 1 integron (intI1). In three of these four strains, the presence of dfrA/sul1 and qacEΔ1 gene cassettes correlated with resistance to co-trimoxazole and high MICs of QACs. In all of the five strains, overexpression of tolC, marOR and soxS was always associated with higher MICs of antibiotics and/or QACs. PAβN reduced the MICs of ciprofloxacin and QACs, suggesting that extrusion of ciprofloxacin and QACs from bacteria depends on the AcrAB–TolC system. Conclusions To our knowledge, this report is the first to describe dual involvement of the AcrAB–TolC system and class 1 integrons in clinical E. coli strains. [ABSTRACT FROM AUTHOR]

Aquatic environments are known reservoirs of antibiotic-resistant bacteria, but little information is known about the role of Escherichia coli strain subgroups, integrons, and integron-associated gene cassettes in the prevalence of antimicrobial resistance. To address these knowledge gaps, the diversity and distribution of drug-resistant E. coli strains and their integrons in hospital wastewater (HWW) and XiaoQing River water (XQRW) in Jinan, China were compared. Phylogenetic assays showed that the isolates were distributed in every E. coli subgroup. The prevalence of antibiotic resistance in each E. coli subgroup from HWW was higher than in subgroups from XQRW, except for phylogenetic subgroup A0. Classes 1 and 2 integrons were found in 327 strains (78.2% of the total 418 isolates) with a prevalence of 85.6% among the 209 isolates from HWW. Among 15 gene cassette arrays, dfrA17- aadA5 and dfrA12-orfF-aadA2 were the most prevalent. The prevalence of drug-resistance gene cassettes and diversity of arrays further proved that integrons were important contributors to the widespread occurrence of antibiotic resistance in E. coli among Jinan aquatic environments. [ABSTRACT FROM AUTHOR]

1. Bacterial resistance to β-lactam antibiotics has risen dramatically inEscherichia colifrom food animals. In a previous study, 29 randomly selected chicken products, collected in Portugal, were analysed for the presence of extended-spectrum β-lactamases (ESBLs)-producingE. coli; and during this study the genetic characterisation of ESBLs genes was investigated. 2. The presence of genes encoding TEM, OXA, SHV, and CTX-M type beta-lactamases was studied by PCR followed by sequencing. Additionally, other mechanisms of antimicrobial resistance, phylogenetic groups and the presence of virulence determinants were evaluated among the isolates. 3. β-lactamases genes were identified as follows:blaCTX-M-14(n = 4),blaCTX-M-1(n = 2),blaCTX-M-9(n = 4) andblaTEM-52(n = 13). Mutations at positions −42, −18, −1, and +58 ofampCpromoter region were identified in 4 non-ESBL-producing isolates. Thetet(A) ortet(B) genes were identified in all tetracycline-resistant isolates; theaadAgene detected in 8 of 10 streptomycin-resistant isolates; theaac(3)-II gene in all gentamicin-resistant isolates; thecmlAgene in the chloramphenicol-resistant isolate; andsul1and/orsul2 and/orsul3genes were found in all trimethoprim-sulfamethoxazole-resistant isolates. TheintI1gene was detected in 8 trimethoprim-sulfamethoxazole-resistant isolates and theintI2gene in 4 isolates; one gene cassette arrangements were identified among class 1 integrons (dfrA1 + aadA1) and among the class 2 integrons (dfrA1 + sat2 + aadA1). Among cefotaxime-resistant isolates, 16 belonged to A or B1 phylogenetic groups, while 11 isolates were classified into the D or B2 phylogroups. At least one virulence-associated gene (aer,fimA, orpapC) was detected in 74·1% of the cefotaxime-resistant isolates. 4. Because ESBLs-producing bacteria are resistant to a broad range of β-lactams, infections caused by these organisms complicate therapy and limit treatment options. [ABSTRACT FROM AUTHOR]

Antibiotic susceptibility, detection of sul gene types and presence of class 1, 2 and 3 integrons and gene cassettes using PCR assays were investigated in 3456 Escherichia coli isolates obtained from 38 sampling sites of the Dongjiang River catchment in the dry and wet seasons. 89.1% of the isolates were resistant and 87.5% showed resistance to at least three antibiotics. sul2 was detected most frequently in 89.2% of 1403 SXT-resistant isolates. The presence of integrons (class 1 and 2) was frequently observed (82.3%) while no class 3 integron was found. In these integrons, 21 resistance genes of 14 gene cassette arrays and 10 different families of resistance genes were identified. Three gene cassette arrays, aac(6'')-Ib-cr-aar-3-dfrA27-aadA16, aacA4-catB3-dfrA1 and aadA2-lnuF, were detected for the first time in surface water. The results showed that bacterial resistance in the catchment was seriously influenced by human activities, especially discharge of wastewater. [Copyright &y& Elsevier]

Abstract: Forty-eight prevalent strains of Riemerella anatipestifer (RA) isolated in China were tested for susceptibility to eighteen antibiotics and investigated for the frequencies and characteristics of integrons and gene cassettes. All isolates were resistant to between three and ten antimicrobial drugs. Forty-seven isolates contained class 1 integron (97.92%), and 15 of the 47 isolates contained class 2 integron (31.25%). Class 3 integron was not detected in the strains analysed. Three different cassette arrays (aadA1, aadA5 and aacA4–aadA1) of class 1 integron and one gene cassette (sat2–aadA1) of class 2 integron were discovered. Three out of the four cassette arrays were novel, with the exception of aadA5. The location of integrons was confirmed by transforming extracted plasmids into an integron-negative strain of Escherichia coli (E. coli) BL21 (DE3). Class 1 integrons were always discovered in plasmids, while class 2 integrons could be located on plasmids or in the chromosome. This is the first description of class 2 integrons, three novel cassette arrays and the location of integrons in RA species. [Copyright &y& Elsevier]

Aims: To characterize class 1 integrons and resistance genes in tetracycline-resistant Escherichia coli originating from beef cattle subtherapeutically administered chlortetracycline (A44), chlortetracycline and sulfamethazine (AS700), or no antimicrobials (control). Methods and Results: Tetracycline-resistant E. coli (control, n = 111; AS700, n = 53; A44, n = 40) were studied. Class 1 integrons, inserted gene cassettes and the presence of other antimicrobial resistance genes, as well as phylogenetic analysis, were performed by PCR, restriction enzyme analysis and sequencing. Susceptibilities to 11 antimicrobials were conducted on all isolates. Prevalence of class 1 integrase was higher ( P < 0·001) in isolates from AS700 (33%) and A44 (28%) steers as compared to control (7%). Most integron gene cassettes belonged to the aad or dfr families. Correlations were found between the tet(A) gene and the genetic elements sul1 ( r = 0·44), aadA1 ( r = 0·61), cat ( r = 0·58) and intI1( r = 0·37). Both closely and distantly related isolates harboured integrons with identical gene cassette arrays. Conclusions: Subtherapeutic administration of chlorotetracycline alone or in combination with sulfamethazine may select for class 1 integrons in bovine tetracycline-resistant E. coli isolates. Vertical spread and horizontal transfer are responsible for the dissemination of a particular type of class 1 integron, but this study could not differentiate if this phenomenon occurred within or outside of the feedlot. Tetracycline-resistant E. coli strains with sul1 and tet(A) genes were more likely to harbour class 1 integrons. Significance and Impact of the Study: Subtherapeutic use of chlortetracycline and sulfamethazine may promote the presence of class 1 integrons in tetracycline-resistant E. coli isolated from feedlot cattle. [ABSTRACT FROM AUTHOR]

The article reports on the presence of highly resistant Escherichia coli strains in Kenya carrying transferrable genes conferring broad resistance to many classes of antibiotics. It mentions that the clinical strains were non-clonal and belonged to phylogenetic groups B1, B2 and D, with two B2 strains belonging to the ST131 clonal complex. It cites the resistance of donors and transconjugants to trimethoprim, tetracyclines and penicillins. It adds that isolates producing extended-spectrum β-lactamases (ESBL) were resistant to most cephalosporins.

Aims: To compare the distribution of integrons and trimethoprim–sulfamethoxazole resistance genes among Escherichia coli isolates from humans and food-producing animals. Methods and Results: A collection of 174 multidrug-resistant E. coli isolates obtained from faecal samples of food-producing animals ( n = 64) and humans ( n = 59), and patients with urinary tract infections ( n = 51) in Hong Kong during 2002–2004 were studied. The strains were analysed for their phylogenetic groups, the presence of sul genes ( sul1 and sul2), integrons ( intl1 and intl2) and class 1 integron-associated dfr cassette genes by PCR, restriction enzyme analysis and sequencing. Integrons were identified in 110 (63·2%) isolates. The prevalence of integrons was significantly different according to the specimen sources (animal faecal 84·4%, human faecal 67·8% and human urinary 31·4%) and phylogenetic groups (B1 80·8%, A 77·6%, D 54·1% and B2 11·5%). Faecal isolates (both human and animal) are more likely to belong to group A and B1. In contrast, most urinary isolates were either groups B2 and D. Among dfr containing isolates, dfrA1 and dfrA12 were almost exclusively found in strains of phylogenetic groups A and B1; and were present in animal and human faecal isolates. In contrast, dfrA17 was found in both faecal and urinary isolates and comprised strains from all phylogenetic groups. The sul1 and sul2 genes were equally prevalent among the isolates irrespective of the specimen source and phylogenetic group status. Pulsed-field gel electrophoresis analysis of isolates with identical cassette genes showed that they were genetically diverse. Conclusions: More animal faecal isolates carry class 1 integrons than human faecal and human urinary isolates, and the distribution of phylogenetic groups is common across animal and human faecal isolates but different from human urinary isolates. Significance and Impact of the Study: Commensal isolates from food-producing animals are an important reservoir for integrons carrying antibiotic resistance genes. [ABSTRACT FROM AUTHOR]

A multiple PCR for the detection of the integrase genes of the three classes of integrons was carried out, and their gene cassettes were characterized in 111 clinical strains of Escherichia coli isolated in Guangzhou City, China during the last 6 years. IntI1 and intI2 genes were detected in 95 isolates (85.6%) and four isolates (3.6%), respectively. No intI3 gene was detected. Six different gene cassettes were found in these strains, and a high prevalence of dfr and aad genes was observed. The E. coli isolates that contained a 1664-bp amplicon of dfrA17-aadA5 in class 1 integron were found to be phylogenetically unrelated to each other by using the enterobacterial repetitive intergenic consensus PCR, as the cassette could be transferred to recipient strains, indicating that the gene cassettes might be disseminated in the clinical strains by a horizontal gene transfer. Therefore, it is important that guidelines for the prudent use of antimicrobial agents are adopted and surveillance programs are established. [ABSTRACT FROM AUTHOR]

The exchange of genes between bacterial chromosome and plasmid(s) and their integration into integrons are mainly responsible for acquisition and dissemination of antibiotic resistance. We investigated the role of integrons and their underlying molecular mechanisms leading to development of adaptability in E. coli and eventual resistance to antimicrobials. Escherichia coli isolates (n = 120); including 40 diarrheagenic isolates, an even number of isolates from cases other than diarrhea, and equal number of isolates from healthy children recovered from fresh stool samples were used for identification of integron genes and gene cassettes. The association of integrons with antibiotic resistance was assayed before phylogenetic analysis. DNA sequence analysis revealed class 1 and 2 integrons in 55.83% and 21.66% isolates, respectively. The integron presence was found significantly associated with the probability of antibiotic resistance in E. coli ; the association being highest with class 1 integron. Modelling and molecular docking along with molecular dynamics simulation analyses found ceftriaxone and amoxicillin as potential inhibitors of dihydrofolate reductase (DHFR). The class 1 integrons of these pathogenic isolates can serve as prospective therapeutic targets using specific silencing strategies and combinational antimicrobial therapy. The findings may be useful for the development of a potent and versatile drug for DHFR inhibition. • Presence of class 1 integrons in >50% of E. coli isolates confer drug resistance. • The integrons of multidrug resistant isolates can be potential therapeutic targets. • Modelling and molecular docking analyses found potential inhibitors of DHFR. [ABSTRACT FROM AUTHOR]

Multidrug-resistant Escherichia coli and antibiotic-resistance genes (ARGs) present a danger to public health. However, information on the dissemination potentials of antibiotic resistance among bacteria from different environments is lacking. We isolated multiple antibiotic-resistant Escherichia spp. from animal farms, hospitals, and municipal wastewater-treatment plants (MWWTPs) using culture-based methods, and carried out resistance phenotype and gene analyses. Thirty-five isolates of multiple antibiotic-resistant Escherichia spp. were further screened to detect 61 ARGs, 18 mobile genetic elements (MGEs), and gene cassettes. The isolates from livestock manure and MWWTPs showed greater diversity in plasmid profiling than hospital wastewater. Each Escherichia sp. carried 21–26 ARGs and 8–12 MGEs. In addition, 11 gene cassettes were detected in 34 Escherichia isolates, with greater diversity in livestock manure and MWWTPs than in hospital wastewater. The results indicated that the potential for ARG transfer was higher in livestock manure and MWWTPs compared with human clinical sources, possibly related to the high occurrence of both residual antibiotics and heavy metals in these environments. Image 1 • The transfer potential of ARGs was compared in Escherichia from different sources. • Each of the Escherichia strains carried at least 1 plasmid, 21 ARGs and 8 MGEs. • High prevalence of gene bla CTX-M was detected in the Escherichia isolates. • Higher ARGs transfer potential in livestock manure and MWWTPs than hospital source. [ABSTRACT FROM AUTHOR]