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 271 records · Page 15Linked to original sources
PubMed2005

Incidence of class 1 integrons in a quaternary ammonium compound-polluted environment.

Samples of effluent and soil were collected from a reed bed system used to remediate liquid waste from a wool finishing mill with a high use of quaternary ammonium compounds (QACs) and were compared with samples of agricultural soils. Resistance quotients of aerobic gram-negative and gram-positive bacteria to ditallowdimethylammomium chloride (DTDMAC) and cetyltrimethylammonium bromide (CTAB) were established by plating onto nutrient agar containing 5 microg/ml or 50 microg/ml DTDMAC or CTAB. Approximately 500 isolates were obtained and screened for the presence of the intI1 (class 1 integrase), qacE (multidrug efflux), and qacE Delta1 (attenuated qacE) genes. QAC resistance was higher in isolates from reed bed samples, and class 1 integron incidence was significantly higher for populations that were preexposed to QACs. This is the first study to demonstrate that QAC selection in the natural environment has the potential to coselect for antibiotic resistance, as class 1 integrons are well-established vectors for cassette genes encoding antibiotic resistance.

Bacteria↗
PubMed2005

OXA-46, a new class D beta-lactamase of narrow substrate specificity encoded by a blaVIM-1-containing integron from a Pseudomonas aeruginosa clinical isolate.

A novel OXA-type enzyme, named OXA-46, was found to be encoded by a gene cassette inserted into a class 1 integron from a multidrug-resistant Pseudomonas aeruginosa clinical isolate. The variable region of the integron also contained a bla(VIM-1) metallo-beta-lactamase cassette and a duplicated aacA4 aminoglycoside acetyltransferase cassette. OXA-46 belongs to the OXA-2 lineage of class D beta-lactamases. It exhibits 78% sequence identity with OXA-2 and the highest similarity (around 92% identity) with another OXA-type enzyme detected in clinical isolates of Burkholderia cepacia and in unidentified bacteria from a wastewater plant. Expression of bla(OXA-46) in Escherichia coli decreased susceptibility to penicillins and narrow-spectrum cephalosporins but not to extended-spectrum cephalosporins, cefsulodin, aztreonam, or carbapenems. The enzyme was overproduced in E. coli and purified by two anion-exchange chromatography steps (approximate yield, 6 mg/liter). OXA-46 was made of a 28.5-kDa polypeptide and exhibited an alkaline pI (7.8). In its native form OXA-46 appeared to be dimeric, and the oligomerization state was not affected by EDTA. Kinetic analysis of OXA-46 revealed a specificity for narrow-spectrum substrates, including oxacillin, other penicillins (but not temocillin), and narrow-spectrum cephalosporins. The enzyme apparently did not interact with temocillin, oxyimino-cephalosporins, or aztreonam. OXA-46 was inactivated by tazobactam and carbapenems and, although less efficiently, also by clavulanic acid. Enzyme activity was not affected either by EDTA or by divalent cations and exhibited low susceptibility to NaCl. These findings underscore the functional and structural diversity that can be encountered among class D beta-lactamases.

Amino Acid Sequence↗
PubMed2005

Integron-associated antibiotic resistance and phylogenetic grouping of Escherichia coli isolates from healthy subjects free of recent antibiotic exposure.

The study of integrons in 181 Escherichia coli isolates from three groups of healthy subjects who lived in communities and had not taken antibiotics for at least 1 month showed that the presence of integrons was associated with antibiotic resistance and phylogenetic grouping of the bacterial host and dependent on a subject's living environment.

Anti-Bacterial Agents↗
PubMed2005

IS26-associated In4-type integrons forming multiresistance loci in enterobacterial plasmids.

Three distinct multiresistant loci from enterobacterial plasmids each comprised an integron and an IS26-associated sequence. Sequence comparison suggested a common ancestral structure that derived from an IS26 insertion into the 5' conserved segment of an In4-type integron and evolved through acquisition of gene cassettes and IS26-mediated recruitment of additional resistance genes of diverse origin.

Cloning, Molecular↗
PubMed2005

BEL-1, a novel clavulanic acid-inhibited extended-spectrum beta-lactamase, and the class 1 integron In120 in Pseudomonas aeruginosa.

Screening by a double-disk synergy test identified a Pseudomonas aeruginosa isolate that produced a clavulanic acid-inhibited expanded-spectrum beta-lactamase (ESBL). Cloning and sequencing identified a novel ESBL, BEL-1, weakly related to other Ambler class A ESBLs. beta-Lactamase BEL-1 hydrolyzed significantly most expanded-spectrum cephalosporins and aztreonam, and its activity was inhibited by clavulanic acid, tazobactam, cefoxitin, moxalactam, and imipenem. This chromosome-encoded ESBL gene was embedded in a class 1 integron containing three other gene cassettes. In addition, this integron was bracketed by Tn1404 transposon sequences at its right end and by P. aeruginosa-specific sequences at its left end.

Amino Acid Sequence↗
PubMed2005

Class 1 integrons and tetracycline resistance genes in alcaligenes, arthrobacter, and Pseudomonas spp. isolated from pigsties and manured soil.

The presence of tetracycline resistance (Tc(r)) genes and class I integrons (in-1), and their ability to cotransfer were investigated in Tc(r) gram-negative (185 strains) and gram-positive (72 strains) bacteria from Danish farmland and pigsties. The isolates belonged to the groups or species Escherichia coli, Enterobacter spp., Arthrobacter spp., Alcaligenes spp., Pseudomonas spp., and Corynebacterium glutamicum. The 257 isolates were screened for in-1. Eighty-one of the gram-negative isolates were also screened for the Tc(r) genes tet(A), tet(B), and tet(C), and all (n = 72) gram-positive isolates were screened for tet(33). Fourteen (7%) of the soil isolates and eleven (25%) of the pigsty isolates contained in-1. All isolates that contained tet genes also contained in-1, except one gram-negative isolate from a pigsty that contained tet(B). All gram-positive isolates with in-1 also contained tet(33). No isolates contained more than one tet gene. The in-1-positive isolates were tested for resistance to selected antimicrobial agents and showed resistance to three to nine drugs. Filter-mating experiments showed cotransfer of Tc(r) and class I integrons from soil isolates to Escherichia coli and/or Pseudomonas putida. We conclude that soil bacteria in close contact to manure or pigsty environment may thus have an important role in horizontal spread of resistance. Use of tetracyclines in food animal production may increase not only Tc(r) but also multidrug resistance (caused by the presence tet genes and in-1) in bacteria.

Alcaligenes↗
PubMed2005

Comparative study of class 1 integron and Vibrio cholerae superintegron integrase activities.

Superintegrons (SIs) and multiresistant integrons (MRIs) have two main structural differences: (i) the SI platform is sedentary, while the MRI platform is commonly associated with mobile DNA elements and (ii) the recombination sites (attC) of SI gene cassette clusters are highly homogeneous, while those of MRI cassette arrays are highly variable in length and sequence. In order to determine if the latter difference was correlated with a dissimilarity in the recombination activities, we conducted a comparative study of the integron integrases of the class 1 MRI (IntI1) and the Vibrio cholerae SI (VchIntIA). We developed two assays that allowed us to independently measure the frequencies of cassette deletion and integration at the cognate attI sites. We demonstrated that the range of attC sites efficiently recombined by VchIntIA is narrower than the range of attC sites efficiently recombined by IntI1. Introduction of mutations into the V. cholerae repeats (VCRs), the attC sites of the V. cholerae SI cassettes, allowed us to map positions that affected the VchIntIA and IntI1 activities to different extents. Using a cointegration assay, we established that in E. coli, attI1-x-VCR recombination catalyzed by IntI1 was 2,600-fold more efficient than attIVch-x-VCR recombination catalyzed by VchIntIA. We performed the same experiments in V. cholerae and established that the attIVch-x-VCR recombination catalyzed by VchIntIA was 2,000-fold greater than the recombination measured in E. coli. Taken together, our results indicate that in the V. cholerae SI, the substrate recognition and recombination reactions mediated by VchIntIA might differ from the class 1 MRI paradigm.

Base Sequence↗
PubMed2003

Spread of integron-associated VIM-type metallo-beta-lactamase genes among imipenem-nonsusceptible Pseudomonas aeruginosa strains in Greek hospitals.

Fifty-eight imipenem-nonsusceptible (MIC >or= 8 microg/ml) Pseudomonas aeruginosa strains isolated during May 2001 in 15 Greek hospitals were studied. Thirty-six isolates derived from nine hospitals carried VIM-type metallo-beta-lactamase genes, as found by PCR. In 34 isolates, bla(VIM) was associated with class 1 integrons of various sizes. DNA sequencing indicated the presence of bla(VIM-2) gene cassettes in a variety of integron structures. Random amplified polymorphic DNA typing suggested diversity of the bla(VIM)-positive strains. Synergy between 2-mercaptoacetic acid and imipenem indicated carbapenemase activity in 26 bla(VIM)-positive strains.

DNA, Bacterial↗
PubMed2005

Identification of Shigella sonnei biotype g isolates carrying class 2 integrons in Italy (2001 to 2003).

Phenotyping and genotyping have been carried out on 64 epidemic and sporadic isolates of Shigella sonnei identified in Italy in the years 2001 to 2003. Class 2 integron carriage has been also investigated. Isolates from four of the five outbreaks and four of six sporadic cases were biotype g, pulsed-field gel electrophoresis type B, and class 2 integron positive, suggesting emergence and spread of an epidemic clone in Italy.

Base Sequence↗
PubMed2004

[Integrons and resistance gene cassettes: structure and role against antimicrobials].

Bacteria have developed sophisticated and successful genetic mechanisms to evade the action of antimicrobials. Bacterial multiresistance has caused serious problems in the treatment of nosocomial infections. Integrons and gene cassettes are considered the main genetic elements in the evolution of plasmids and transposons that actively participate in the mobilization of genes, codifying different bacterial resistance mechanisms. This article reviews the historical and structural aspects of integrons and resistance gene cassettes and the presence of these structures in gram negative bacteria isolated from Chilean hospitals in the last ten years.

Anti-Bacterial Agents↗
PubMed2005

Changes in patterns of antimicrobial susceptibility and class 1 integron carriage among Escherichia coli isolates.

The worldwide use of antimicrobials in different fields has created enormous pressure for the selection of resistance among opportunistic bacterial pathogen. One hundred four E. coli isolates were collected and identified from swine with diarrhea in Korea during the period of 2002. The isolates showed highly resistant to streptomycin (99.0%), tetracycline (97.1%), neomycin (91.3%) and carbenicillin (84.6%) in antimicrobial susceptibility test. Moreover, all of the isolates showed multiple antimicrobial resistant to more than 3, and 85% of them were resistant to more than 7 of total 14 antimicrobial agents. In comparison with isolates in 1998, resistance to antimicrobials was more frequent among the isolates in 2002. Presence of class 1 integrons was investigated through amplification of the gene with PCR, and could be classified 8 groups by pattern of 4 different amplicons. Class 1 integrons were observed in 67 strains (64.2%) of E. coli from swine in Korea. One and 1.6 kbp of amplicons were revealed to contain aadA1 and aadB-aadA1 gene cassettes respectively. Two kbp of amplicon had three different gene cassettes, dhfrXII-orfF-aadA2, and 3.0 kbp of amplicon includes aadB-cmlA1 gene cassettes.

Animals↗
PubMed1993

Tn5053, a mercury resistance transposon with integron's ends.

We describe a novel type of mercury resistance transposon, Tn5053, which was found in the chromosome of a mercury-resistant Xanthomonas strain isolated from a mercury mine. An 8400 base-pair Tn5053 is bracketed by 25 base-pair inverted repeats that have no sequence homology with inverted repeats of classical mercury resistance transposons Tn501 and Tn21. Instead they show high homology with inverted repeats bracketing the antibiotic resistance segment of Tn21 (integron In2). A 38 base-pair element, which is highly homologous to the inverted repeats of classical mercury resistance transposons has been found within Tn5053 near one of its ends. This internal inverted repeat is fused to the mer operon of Tn5053 in exactly the same way as in the Tn501 mercury resistance transposon. This finding suggests that the mer operon was integrated into the Tn5053 transposition module not through integron-specific pathway but rather via insertion of a classical mercury resistance transposon.

Base Sequence↗
PubMed2006

Structural basis for broad DNA-specificity in integron recombination.

Lateral DNA transfer--the movement of genetic traits between bacteria--has a profound impact on genomic evolution and speciation. The efficiency with which bacteria incorporate genetic information reflects their capacity to adapt to changing environmental conditions. Integron integrases are proteins that mediate site-specific DNA recombination between a proximal primary site (attI) and a secondary target site (attC) found within mobile gene cassettes encoding resistance or virulence factors. The lack of sequence conservation among attC sites has led to the hypothesis that a sequence-independent structural recognition determinant must exist within attC. Here we report the crystal structure of an integron integrase bound to an attC substrate. The structure shows that DNA target site recognition and high-order synaptic assembly are not dependent on canonical DNA but on the position of two flipped-out bases that interact in cis and in trans with the integrase. These extrahelical bases, one of which is required for recombination in vivo, originate from folding of the bottom strand of attC owing to its imperfect internal dyad symmetry. The mechanism reported here supports a new paradigm for how sequence-degenerate single-stranded genetic material is recognized and exchanged between bacteria.

Attachment Sites, Microbiological↗
PubMed2002

Nosocomial spread of the integron-located veb-1-like cassette encoding an extended-pectrum beta-lactamase in Pseudomonas aeruginosa in Thailand.

The beta-lactamase gene content and epidemiology of ceftazidime-resistant Pseudomonas aeruginosa isolates (24% of the total number of P. aeruginosa isolates) were investigated at a University Hospital in Thailand during a 4-month period in 1999. Of 33 nonrepetitive clinical isolates, 31 produced a VEB-1-like clavulanic acid-inhibited extended-spectrum beta-lactamase (ESBL). These isolates belonged to different pulsed-field gel electrophoresis types and subtypes. In 1 case, the bla(VEB-1)-like gene was plasmid located. The bla(VEB-1)-like genes were present as a gene cassette on class 1 integrons that varied in size and structure. In most cases, the veb-1 cassette was associated with an arr-2 cassette (rifampin resistance), aminoglycoside resistance gene cassettes, and an oxa-10-like cassette encoding a narrow-spectrum oxacillinase-type beta-lactamase. The present study indicates that ESBLs may be endemic in P. aeruginosa and illustrates that integrons are efficient means for their spread.

Ceftazidime↗
PubMed2000

An integron cassette carrying dfr1 with 90-bp repeat sequences located on the chromosome of trimethoprim-resistant isolates of Campylobacter jejuni.

The frequent occurrence of high-level trimethoprim resistance in clinical isolates of Campylobacter jejuni was shown to be related to the acquisition of foreign resistance genes (dfrl or dfr9 or both) coding for resistant variants of the enzyme dihydrofolate reductase, the target of trimethoprim. The dfr1 gene detected on the chromosome of 40 different clinical strains of C. jejuni was studied further regarding structure and genetic organization. Most of the dfr1 genes were found as integron cassettes inserted in the chromosome. In 36% of the examined isolated, the dfr1 gene showed identity to that previously characterized in trimethoprim-resistant Escherichia coli. In 40% of the cases, however, a variant of the dfr1 gene containing a 90-bp direct repeat was detected, and in 5% of the isolates, the repeat-containing dfr1 variant was found to occur in the form of two cassettes in tandem in an integron context. The existence of the 90-bp repeat within the coding sequence of the dfr1gene was found to play a role in the adaptation of C. jejuni to ambient concentrations of trimethoprim.

Amino Acid Sequence↗
PubMed2000

Characterization of aminoglycoside resistance genes and class 1 integrons in porcine and bovine gentamicin-resistant Escherichia coli.

A total of 78 gentamicin-resistant Escherichia coli strains from swine (27) and cattle (51) were characterized by phenotypic resistance, presence of selected aminoglycoside resistance genes, class 1 integrons and gene cassettes, and pulsed-field gel electrophoresis. Gentamicin resistance was mainly encoded by the ant(2'')-I gene that was found in 76% of all the strains investigated, whereas the aac(3)-IIa gene was found in 14%. The ant(2'')-I gene was predominant in strains from cattle, whereas the porcine strains contained both ant(2'')-I, aac(3)-IIa, and the aac(3)-IVa genes. The pulsed-field gel electrophoresis (PFGE) investigation indicated a close clonal relationship in half of the bovine strains whereas the remaining E. coli were unrelated. Among the E. coli investigated, 20% contained class 1 integrons. Genes encoding resistance to trimethoprim (dhfrI, dhfrIb, and dhfrVII), gentamicin, tobramycin, and kanamycin (ant(2'')-Ia streptomycin and spectinomycin (ant(3'')-Ia) and streptothricin (sat1) were identified as gene cassettes. The most prevalent gene cassettes were ant(3'')-Ia (11 isolates) and the dhfrI (nine isolates).

Animals↗
PubMed2000

Two new gene cassettes, dfr17 (for trimethoprim resistance) and aadA4 (for spectinomycin/streptomycin resistance), inserted in an Escherichia coli class 1 integron.

Two new gene cassettes, dfr17 and aadA4, inserted in a class 1 integron of Escherichia coli EC107, are described here. The dfr17 cassette encodes trimethoprim resistance and has 91% identity with the dfrVII dihydrofolate reductase gene. The aadA4 cassette confers resistance to spectinomycin and streptomycin and shows 94% identity with the aadA3 gene. The integron carrying the dfr17 and aadA4 cassettes was located on a conjugative plasmid, pEC1072.

DNA Transposable Elements↗