New integron-associated gene cassette encoding a trimethoprim-resistant DfrB-type dihydrofolate reductase.

A sixth gene cassette containing a dfrB-type gene, dfrB6, was found in a dfrB6-aadA1 cassette array in class 1 integrons. This array was isolated from several multiply antibiotic-resistant Salmonella enterica serovar Infantis strains that appear to be clonally related. The DfrB6 dihydrofolate reductase conferred resistance to trimethoprim.

Aquariums as reservoirs for multidrug-resistant Salmonella Paratyphi B.

Multidrug-resistant Salmonella enterica serovar Paratyphi B dT+ isolates from patients with gastroenteritis were identical with isolates from their home aquariums. Matched isolates had identical phage types, XbaI and IS200 profiles, and Salmonella genomic island 1 (SGI1). Ornamental fish tanks are reservoirs for SGI1-containing S.

Do operator volumes relate to clinical outcomes after percutaneous coronary intervention in the Canadian health care system?

Background: Many US studies have documented an association between operator volume and outcomes after percutaneous coronary intervention (PCI). No study has assessed whether this relationship exists in Canada, where PCI is performed only at a limited number of regional centers and operator volumes are higher.

Methods: All PCI procedures performed in the province of Ontario from 1995 to 2001 were analyzed using administrative databases.

Recombination between the dfrA12-orfF-aadA2 cassette array and an aadA1 gene cassette creates a hybrid cassette, aadA8b.

Homologous recombination between closely related gene cassettes, such as aadA1 and aadA2, which are 89% identical, can create hybrid cassettes and hybrids of existing cassette arrays. A new cassette array, dfrA12-orfF-aadA8b, which was created by such a recombination event occurring within the aadA2 cassette in the dfrA12-orfF-aadA2 array, has been identified.

The genomic island SGI1, containing the multiple antibiotic resistance region of Salmonella enterica serovar Typhimurium DT104 or variants of it, is widely distributed in other S. enterica serovars.

The global dissemination of the multiply-antibiotic-resistant Salmonella enterica serovar Typhimurium DT104 clone with the resistance genes located in a class 1 integron, here designated In104, within genomic island SGI1 is a significant public health issue. Here, we have shown that SGI1 and variants of it carrying different combinations of resistance genes are found in several Salmonella enterica serovars. These are serovars Cerro, Derby, Dusseldorf, Infantis, Kiambu, and Paratyphi B dT(+) isolated from human infections and serovar Emek from sewage effluent.

New integron-associated gene cassette encoding a 3-N-aminoglycoside acetyltransferase.

A fifth gene cassette containing an aacC gene, aacCA5, was found in an aacCA5-aadA7 cassette array in a class 1 integron isolated from a multiply drug resistant Salmonella enterica serovar Kentucky strain. The AacC-A5 or AAC(3)-Ie acetyltransferase encoded by aacCA5 is related to other AAC(3)-I enzymes and confers resistance to gentamicin.

Complex multiple antibiotic and mercury resistance region derived from the r-det of NR1 (R100).

The sequence of the 45.2-kb multidrug and mercury resistance region of pRMH760, a large plasmid from a clinical isolate of Klebsiella pneumoniae collected in 1997 in Australia, was completed. Most of the modules found in the resistance determinant (r-det), or Tn2670, region of NR1 (also known as R100), isolated from a Shigella flexneri strain in Japan in the late 1950s, were present in pRMH760 but in a different configuration.

Regional outcomes of heart failure in Canada.

Background: Heart failure is a condition associated with significant mortality and morbidity. However, demographic features and outcomes following hospitalization for heart failure, and associated regional comparisons have not been performed in Canada.

Methods: Anonymously rendered records of patients hospitalized for incident heart failure in Canada were selected from the Canadian Institute for Health Information discharge abstract and hospital morbidity databases from fiscal years 1997/1998 to 1999/2000.

Comparison of the structure-activity relationships of the integron-associated recombination sites attI3 and attI1 reveals common features.

Incorporation of gene cassettes into integrons occurs by IntI-mediated site-specific recombination between a 59-base element (59-be) site in the cassette and an attI site in the integron. While the 59-be sites share common features and are recognized by several different IntI recombinases, the sequences of attI sites are not obviously related and are preferentially recognized by the cognate IntI. To determine the features of attI sites that are required for recombination proficiency, the structure-activity relationships of a second attI site, the attI3 site from the class 3 integron, were examined.

The IS1111 family members IS4321 and IS5075 have subterminal inverted repeats and target the terminal inverted repeats of Tn21 family transposons.

IS5075 and IS4321 are closely related (93.1% identical) members of the IS1111 family that target a specific position in the 38-bp terminal inverted repeats of Tn21 family transposons and that are inserted in only one orientation. They are 1,327 bp long and have identical ends consisting of short inverted repeats of 12 bp with an additional 7 bp (TAATGAG) or 6 bp (AATGAG) to the left of the left inverted repeats and 3 bp (AGA) or 4 bp (AGAT) to the right of the right inverted repeat.

Hospitalization rates and length of stay for cardiovascular conditions in Canada, 1994 to 1999.

Background: Cardiovascular diseases (CVDs) are a leading cause of hospitalization in Canada. An examination of recent trends in cardiovascular hospitalization rates across Canada is of considerable value and interest to health policy decision makers and administrators, clinicians and researchers.

Objectives: To examine temporal trends and regional variation in hospitalization rates and length of stay for CVD conditions in Canada.

In34, a complex In5 family class 1 integron containing orf513 and dfrA10.

A complex class 1 integron, In34, found in a conjugative plasmid from a multidrug-resistant Klebsiella pneumoniae strain isolated in 1997 at a hospital in Sydney, Australia, was shown to have a backbone related to that of In2, which belongs to the In5 family. In In34, the aadB gene cassette replaces the aadA1a cassette in In2, and two additional resistance genes, dfrA10 and aphA1, that are not part of a gene cassette are present. The aphA1 gene is in a Tn4352-like transposon that is located in the tniA gene.

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.

Class 1 integron containing a new gene cassette, aadA10, associated with Tn1404 from R151.

The carbenicillin, gentamicin, kanamycin, streptomycin, spectinomycin, sulfonamide, and tobramycin resistance determinants found on Pseudomonas aeruginosa plasmid R151 have previously been shown to translocate to another plasmid, R388, and it was inferred that a transposon, Tn1404, carried the resistance determinants. Sequencing of the cassette array from the plasmid known as R388::Tn1404 revealed two known gene cassettes, oxa10 and aadB, and a previously unidentified cassette determining resistance to streptomycin and spectinomycin, here designated aadA10, in the order oxa10-aadB-aadA10. These cassettes replaced the dfrB2-orfA cassette array of R388, indicating that movement of the resistance determinants from R151 to R388 resulted from recombinational exchange between two class 1 integrons rather than transposition.

Efflux of chloramphenicol by the CmlA1 protein.

The cmlA1 gene cassette contains the cmlA1 gene, that confers resistance to chloramphenicol, as well as a promoter and translational attenuation signals, and expression of cmlA1 is inducible by low concentrations of chloramphenicol. The CmlA1 protein encoded by cmlA1 was localised in the inner membrane. Active efflux of chloramphenicol, additional to the endogenous efflux from Escherichia coli cells, was observed when the cmlA1 gene was present and the production of CmlA1 had been preinduced with subinhibitory concentrations of chloramphenicol.

Characterization of the class 3 integron and the site-specific recombination system it determines.

Integrons capture gene cassettes by using a site-specific recombination mechanism. As only one class of integron and integron-determined site-specific recombination system has been studied in detail, the properties of a second class, the only known class 3 integron, were examined. The configuration of the three potentially definitive features of integrons, the intI3 gene, the adjacent attI3 recombination site, and the P(c) promoter that directs transcription of the cassettes, was similar to that found in the corresponding region (5' conserved segment) of class 1 integrons.