Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Integrons”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14Linked to original sources
PubMed2002

Integron-encoded IntI integrases preferentially recognize the adjacent cognate attI site in recombination with a 59-be site.

Integrons have the capacity to capture small mobile elements known as gene cassettes, and this reaction is catalysed by integron-encoded IntI integrases. IntI integrases form a distinct family within the tyrosine recombinase superfamily and include a characteristic additional domain that is well conserved. Two different IntI enzymes were used to examine their ability to recognize heterologous attI sites in both integration and excision assays. IntI1 and IntI3 are 59% identical and catalyse both integrative and excisive recombination between a cassette-associated 59-be site and the cognate attI1 or attI3 site. Integrative recombination events involving a 59-be and a non-cognate attI site, attI2 and attI3 for IntI1 or attI1 and attI2 for IntI3, were detected extremely rarely. In cassette excision assays, the non-cognate attI3 site was recognized by IntI1, but attI1 was not well recognized by IntI3. The purified IntI1 and IntI3 proteins bound strongly only to their cognate attI site.

Amino Acid Sequence↗
PubMed2002

Translocation of integron-associated resistance in a natural system: acquisition of resistance determinants by Inc P and Inc W plasmids from Salmonella enterica Typhimurium DT104.

Salmonella enterica Typhimurium DT104, 961368, a veterinary field isolate that encodes a chromosomal cluster of resistance genes as well as two integrons, was used to study the mobility of resistance cassettes (aadA2 and pse-1) and nonintegron-associated resistance determinants (chloramphenicol and tetracycline). A range of natural plasmids was used as targets for the translocation of resistance. Plasmids that acquired resistance from the DT104 chromosome were segregated by conjugation into Escherichia coli K12. Plasmids R751, R388, and RP4::Tn7 acquired several combinations of resistance determinant (including single cassettes) at frequencies comparable with transposition. RP4 and pOG660 did not acquire any determinants from DT104. Phenotypic and PCR-based analysis of all the transconjugants that were translocated-both cassettes and more complex combinations of determinants-was carried out to determinate the genetic content. Translocation to R751 and R388 was associated with the loss of the indigenous trimethoprim cassette to both plasmids and also acquisition of sulfonamide resistance by R751 and RP4::Tn7, which indicated movement of the 3' terminus of one or both of the DT104 integrons. Sequencing of the R751 transconjugants confirmed these findings and showed that the translocation of streptomycin and ampicillin cassettes was associated with the precise excision of dhfrIIc and orfD cassettes. Furthermore, the translocation of multiple determinants occurred by at least two mechanisms, one of which was likely to involve a circular intermediate analogous to a composite cassette. Instability was detected in some of the transconjugants. The implication of the findings for the dissemination of resistance among clinical isolates is discussed.

Chloramphenicol↗
PubMed2005

Class 1 integrons in Enterobacteriaceae isolated from clinical infections of horses and dogs in the Netherlands.

Integrons in gentamicin- and cotrimoxazole-resistant Enterobacteriaceae from dogs and horses with clinical infections were analyzed by conserved segment PCR-RFLP. Five distinct integron types were found, most of which have previously been reported in Enterobacteriaceae isolated from humans and farm animals, indicating that resistance genes are exchanged between the reservoirs in humans, farm animals, and companion animals.

Amino Acid Sequence↗
PubMed2003

Antimicrobial resistance in clinical isolates of Salmonella enterica serotype Enteritidis: relationships between mutations conferring quinolone resistance, integrons, plasmids and genetic types.

In 481 clinical isolates of Salmonella enterica serotype Enteritidis collected from a Spanish region in 2000, 108, 83 and four isolates were resistant, respectively, to nalidixic acid, ampicillin or both. Nalidixic acid resistance was the result of DNA gyrase mutations involving the codons Asp-87 (97 isolates) and Ser-83 (15 isolates) of the gyrA gene; no mutations in parC were detected. In ampicillin-resistant strains, blaTEM genes located on plasmids and/or the chromosome were implicated. Five plasmids containing blaTEM1-like genes were identified, ranging from 7 to 100 kb, four of which were self-transferable; one of these contained a class 1 sul1 integron with an aadA1a gene cassette. This integron was also found on the chromosome of an isolate resistant to ampicillin, streptomycin and sulfadiazine. A relationship between a 40 kb self-transferable plasmid and strains of Salmonella Enteritidis phage type 6a with a distinctive RAPD profile was established.

Ampicillin↗
PubMed2005

Characterization of a 2.6 kbp variable region within a class 1 integron found in an Acinetobacter baumannii strain isolated from a horse.

OBJECTIVES: A complete gene cassette contained in a class 1 integron from a multidrug-resistant (MDR) isolate of Acinetobacter baumannii cultured from a horse was characterized by molecular methods. METHODS: Template genomic DNA purified from the A. baumannii isolate was investigated by PCR. A gene cassette-associated amplicon was detected and completely characterized. RESULTS: A 2.6 kbp DNA fragment containing four gene cassettes was amplified from the MDR A. baumannii isolate. Sequence analysis showed it was similar to sequences recently reported in Klebsiella pneumoniae, Serratia marcescens and an Escherichia coli plasmid p1658/97 which conferred aminoglycoside resistance. Aminoglycoside resistance-encoding genes aacC1 and aadA1 were located within the 2.6 kbp amplicon, separated by two open reading frames (ORFs) coding for unknown products. This cassette structure (and some variants) was identified in unrelated Acinetobacter spp. from human sources, based on sequence comparisons of the current databases. CONCLUSIONS: Identification of a complete class 1 integron in an equine isolate of A. baumannii suggests that the screening of isolates from animals for these elements should be considered, as this information could influence the selection of chemotherapeutic agents.

Acinetobacter baumannii↗
PubMed2005

Macrolide inactivation gene cluster mphA-mrx-mphR adjacent to a class 1 integron in Aeromonas hydrophila isolated from a diarrhoeic pig in Oklahoma.

OBJECTIVES: To characterize a multidrug-resistant Aeromonas hydrophila isolate (CVM861) that possesses a high-level macrolide inactivation gene cluster (mphA-mrx-mphR), previously only reported in Escherichia coli. METHODS: PCR fragment length mapping, gene sequencing and Southern blotting were used to map the mphA-mrx-mphR gene cluster and flanking elements in CVM861. Conjugation experiments were done to determine whether the multidrug resistance genetic element was mobile. RESULTS: The mphA-mrx-mphR gene cluster mapped downstream of a class 1 integron and upstream of an aph(3') gene, and was present on a Tn21-like element. The gene order determined by sequencing was intI1-dhfrXII-orfF-aadA2-qacDeltaE-sul1-orf5Delta178-tnpA-mphR-mrx-mphA. Horizontal transmission of high-level macrolide resistance from CVM861 to E. coli 47011 was inconsistent; however, a composite plasmid possessing the mphA gene cluster was transferred at a conjugation frequency of 2.02 x 10(-5) per recipient. CONCLUSIONS: An mphA-mrx-mphR gene cluster was present downstream of the In2 integron located on a Tn21-like transposon in an A. hydrophila isolate. Whether this recombination event resulted in the truncation of the orf5 sequence is unknown. The presence of other resistance genes downstream of the mphA-mrx-mphR gene cluster suggests that multiple recombination events have occurred on this genetic element. This is the first known report of the mphA-mrx-mphR gene cluster carried by A. hydrophila and the first known isolation of this cluster in the United States.

Aeromonas hydrophila↗
PubMed2006

Molecular characterization of an Escherichia coli clinical isolate that produces both metallo-beta-lactamase VIM-2 and extended-spectrum beta-lactamase GES-7: identification of the In8 integron carrying the blaVIM-2 gene.

OBJECTIVES: We have previously reported the isolation of a VIM-2-producing Escherichia coli clinical isolate and the coexistence of blaVIM-2 and blaGES-7 in the same isolate. The aim of this study was to elucidate the genetic environment of these genes. METHODS: PCR and sequence analysis were used to identify and analyse the blaVIM-containing integron. The location of the blaVIM-2 and blaGES-7 genes was identified by hybridization experiments on I-CeuI-digested genomic DNA after PFGE. RESULTS: Only the blaVIM-2 gene has been found on a class I integron, designated In8 (1474 bp). Hybridization with the blaVIM-2, the blaGES-7 and the 16S-23S rRNA probes confirmed the chromosomal location of both genes. The blaVIM-2 probe hybridized with a 710 kb fragment whereas the blaGES-7 probe hybridized with a 144 kb fragment of genomic DNA of the E. coli isolate. CONCLUSIONS: This report provides evidence for the chromosomal location of both blaVIM-2 and blaGES-7 genes carried by an E. coli clinical isolate. In8, containing blaVIM-2, presents an emerging threat of carbapenem resistance among E. coli isolates in Greece.

Chromosomes, Bacterial↗
PubMed2004

Integron integrase binds to bulged hairpin DNA.

Gene cassettes are short, monogenic DNA elements that translocate between integrons through site-specific excision and integration. These events require that an integron-coded tyrosine recombinase forms a reactive complex with two sites, at least one of which belongs to the attC class. An attC site can be divided into two pairs of short repeats flanking a palindromic central region. The nucleotide sequence of attC among different cassettes varies extensively, implying that the site contains a structural recognition determinant with low sequence constraints. Oligonucleotides representing many different sequence modifications in either strand of the site were examined for integrase binding by using an electrophoresis mobility shift assay. The inner repeats, a central triplet and two single-nucleotide asymmetries in the site had the strongest influence on binding strength and strand choice. Our data show that the recombinase binds to a bulged hairpin in attC and that the hairpin distortion due to bulging could define the appropriate orientation of the otherwise symmetrical site. This is consistent with the strong bias for binding of recombinase to the bottom-strand oligonucleotides in vitro. Moreover, it was observed that the mobility-shifted complexes persisted under protein-denaturing assay conditions, indicating that a covalent link is indeed formed between integrase and DNA. Upon substitution of the presumed DNA-attacking residue, Y312, with a phenylalanine, DNA binding remained but there was no covalent linkage.

Base Sequence↗
PubMed2006

Analysis of integrons in clinical isolates of Escherichia coli in China during the last six years.

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.

Anti-Bacterial Agents↗
PubMed2006

Dissemination and persistence of blaCTX-M-9 are linked to class 1 integrons containing CR1 associated with defective transposon derivatives from Tn402 located in early antibiotic resistance plasmids of IncHI2, IncP1-alpha, and IncFI groups.

This study analyzes the diversity of In60, a class 1 integron bearing CR1 and containing bla(CTX-M-9), and its association with Tn402, Tn21, and classical conjugative plasmids among 45 CTX-M-9-producing clinical strains (41 Escherichia coli strains, 2 Klebsiella pneumoniae strains, 1 Salmonella enterica strain, and 1 Enterobacter cloacae strain). Forty-five patients in a Spanish tertiary care hospital were studied (1996 to 2003). The diversity of In60 and association of In60 with Tn402 or mercury resistance transposons were investigated by overlapping PCR assays and/or hybridization. Plasmid characterization included comparison of restriction fragment length polymorphism patterns and determination of incompatibility group by PCR-based replicon typing, sequencing, and hybridization. CTX-M-9 plasmids belonged to IncHI2 (n = 26), IncP-1alpha (n = 10), IncFI (n = 4), and IncI (n = 1) groups. Genetic platforms containing bla(CTX-M-9) were classified in six types in relation to the In60 backbone and in eight subtypes in relation to Tn402 derivatives. They were associated with Tn21 sequences when located in IncP-1alpha or IncHI2 plasmids. Our study identified bla(CTX-M-9) in a high diversity of CR1-bearing class 1 integrons linked to different Tn402 derivatives, often to Tn21, highlighting the role of recombination events in the evolution of antibiotic resistance plasmids. The presence of bla(CTX-M-9) on broad-host-range IncP-1alpha plasmids might contribute to its dissemination to hosts that were not members of the family Enterobacteriaceae.

DNA Transposable Elements↗
PubMed2003

Epidemiology of rifampin ADP-ribosyltransferase (arr-2) and metallo-beta-lactamase (blaIMP-4) gene cassettes in class 1 integrons in Acinetobacter strains isolated from blood cultures in 1997 to 2000.

We characterized two new gene cassettes in an Acinetobacter isolate: one harbored the metallo-beta-lactamase (IMP-4) gene bla(IMP-4), the other harbored the rifampin ADP-ribosyltransferase (ARR-2) gene arr-2, and both arrayed with the aminoglycoside acetyltransferase [AAC(6')-Ib(7)] gene cassette aacA4 in two separate class 1 integrons. The epidemiology of these gene cassettes in isolates from blood cultures obtained from 1997 to 2000 was studied. Isolates bearing either the bla(IMP-4) or the arr-2 gene cassette or both represented 17.5% (10 of 57) of isolates in 1997, 16.1% (10 of 62) in 1998, 2.5% (1 of 40) in 1999, and 0% (0 of 58) in 2000. These two gene cassettes, probably borne on two separate integrons, were found in at least three genomic DNA groups, with evidence of clonal dissemination in the intensive care unit during 1997 to 1998. Seventeen of the 52 Acinetobacter baumannii (genomic DNA group 2) isolates from 1997 to 2000 harbored intI1, but only one was positive for these gene cassettes, whereas 20 of the 21 intI1-positive isolates of all other genomic DNA groups were positive for either or both of them. Reduced susceptibility to imipenem and rifampin was seen only in isolates harboring the bla(IMP-4) and arr-2 cassettes, respectively. The aminoglycoside phosphotransferase [APH(3')-VIa] gene aph(3')-VIa was detected in all 21 isolates for which the MIC of amikacin was >/=8 micro g/ml, with or without aacA4, whereas aacA4 alone was found in isolates for which the MIC of amikacin was 0.5 to 2 micro g/ml. Significant differences between the 17 intI1-positive and 47 intI1-negative isolates belonging to genomic DNA group 3 from 1997 to 1998 in the MICs of amikacin, gentamicin, imipenem, sulfamethoxazole, and ceftazidime were observed (Mann-Whitney test, P < 0.001 to 0.01).

ADP Ribose Transferases↗
PubMed2003

Integron-associated antibiotic resistance in Salmonella enterica serovar typhi from Asia.

Eighteen of 25 isolates of Salmonella enterica serovar Typhi were multidrug resistant and contained class 1 integrons with a single cassette, dfrVII or aadA1. The dfrVII-containing integron was likely borne on an IncHI1 plasmid. Salmonella serovar Typhi could become resistant to broad-spectrum cephalosporins by integrating cassettes, such as veb-1, a common cassette in Asia.

Asia↗
PubMed2004

Evidence for a chromosomally located third integron in Salmonella enterica serovar Typhimurium DT104b.

Salmonella enterica serovar Typhimurium isolates of phage types DT104 and DT104b are frequently associated with multiple antimicrobial resistance. We describe the characterization of a class 1 integron containing dfrA1 and aadA1, genes from two Salmonella serovar Typhimurium DT104b isolates. Genetic mapping located the integron to the bacterial chromosome in each case.

Blotting, Southern↗
PubMed2004

Antibiotic resistance conferred by a class I integron and SXT constin in Vibrio cholerae O1 strains isolated in Laos.

Changes in the drug susceptibility pattern were observed in Vibrio cholerae O1 isolated in the Lao People's Democratic Republic during 1993 to 2000. In this study, 50 V. cholerae O1 strains were selected during this period for studying the presence of class I integron and SXT constin. Twenty-four streptomycin-resistant strains out of 26 isolated before 1997 contained a class I integron harboring the aadA1 gene cassette. Twenty-four strains isolated after 1997 contained an SXT constin (a large conjugative element). Twenty of the strains were resistant to chloramphenicol, tetracycline, streptomycin, and trimethoprim-sulfamethoxazole, while four strains were susceptible to the antibiotic tested. The resistance genes included in the SXT constins were floR, tetA, strAB, and sulII, which encode resistance to chloramphenicol, tetracycline, streptomycin, and sulfamethoxazole, respectively. The antibiotic resistance gene cluster was found to be deleted in the four susceptible strains. SXT(LAOS) did not contain dfrA1 or dfr18, which confer resistance to trimethoprim in SXT(ET) and SXT(MO10), respectively. A hot spot region of SXT(LAOS) was sequenced, and we identified two novel open reading frames showing homology to sO24 (exonuclease) and sO23 (helicase) of the genomic island associated with the multidrug resistance region of Salmonella enterica serovar Typhimurium DT104. Analysis of SXT(LAOS) showed that there is a continuous flux of genes among V. cholerae SXT constins which should be carefully monitored.

Bacterial Proteins↗
PubMed2005

Dissemination of sulfonamide resistance genes (sul1, sul2, and sul3) in Portuguese Salmonella enterica strains and relation with integrons.

In 200 sulfonamide-resistant Portuguese Salmonella isolates, 152 sul1, 74 sul2, and 14 sul3 genes were detected. Class 1 integrons were always associated with sul genes, including sul3 alone in some isolates. The sul3 gene has been identified in isolates from different sources and serotypes, which also carried a class 1 integron with aadA and dfrA gene cassettes.

Anti-Bacterial Agents↗
PubMed2005

Integrons and transposons on the Salmonella enterica serovar typhimurium virulence plasmid.

A virulence plasmid was identified in a multidrug-resistant Salmonella enterica serotype Typhimurium strain carrying the spvC, rck, and pefA virulence genes and two class 1 integrons linked to the Tn21 and Tn1696 transposons. A novel trimethoprim resistance gene, designated dfrA23, was also identified within the integron region. The association of multidrug resistance and virulence determinants represents an interesting example of virulence plasmid evolution.

Amino Acid Sequence↗