OXA-1 is OXA-30 is OXA-1.
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Amino Acid Sequence↗
Biomedical subjects
David A Boyd
Publications and source records attributed to David A Boyd.
The genetics of Salmonella genomic island 1.
Multidrug-resistant Salmonella enterica serovar Typhimurium phage type DT104, resistant to ampicillin, chloramphenicol/florfenicol, streptomycin, sulfonamides, and tetracycline, has disseminated worldwide. The resistance genes reside on the 43-kb Salmonella genomic island 1 (SGI1), which is transferable. Drug-resistant variants of SGI1 have been identified in numerous serotypes. Strains harboring SGI1 may be more virulent and have a tendency to rapidly disseminate.
Animals↗
Plasmon-assisted chemical vapor deposition.
We introduce a new chemical vapor deposition (CVD) process that can be used to selectively deposit materials of many different types. The technique makes use of the plasmon resonance in nanoscale metal structures to produce the local heating necessary to initiate deposition when illuminated by a focused low-power laser. We demonstrate the technique, which we refer to as plasmon-assisted CVD (PACVD), by patterning the spatial deposition of PbO and TiO(2) on glass substrates coated with a dispersion of 23 nm gold particles. The morphology of both oxide deposits is consistent with local laser-induced heating of the gold particles by more than 150 degrees C. We show that temperature changes of this magnitude are consistent with our analysis of the heat-loss mechanisms. The technique is general and can be used to spatially control the deposition of virtually any material for which a CVD process exists.
Gold↗
VanG-type vancomycin-resistant Enterococcus faecalis strains isolated in Canada.
Enterococcus faecalis G1-0247 (vancomycin MIC, 16 microg/ml) was found to harbor a vanG operon 99% identical to the vanG operon in E. faecalis BM4518. E. faecalis N03-0233 (vancomycin MIC, 16 microg/ml) was found to harbor a novel vanG operon, vanG2, on an element in a different chromosomal location than the vanG-harboring elements in G1-0247 and BM4518.
Anti-Bacterial Agents↗
Enterococcus gallinarum N04-0414 harbors a VanD-type vancomycin resistance operon and does not contain a D-alanine:D-alanine 2 (ddl2) gene.
Enterococcus gallinarum N04-0414 (MIC for vancomycin, 256 microg/ml) harbored a vanD-type vancomycin resistance operon as well as the intrinsic vanC1 operon. The D-Ala:D-Ala ligase 2 gene (ddl2) was not present in the strain, though it is found downstream of the vanS gene from the vanC operon in E. gallinarum ATCC 49573 and 19 other E. gallinarum strains tested.
Alanine↗
Increase in ampC promoter strength due to mutations and deletion of the attenuator in a clinical isolate of cefoxitin-resistant Escherichia coli as determined by RT-PCR.
OBJECTIVES: To characterize the mechanism of cefoxitin resistance in clinical isolate Escherichia coli N99-0001. METHODS: Plasmid analysis, PCR for beta-lactamases, and sequencing of the ampC genes was carried out. An RT-PCR method was developed to determine relative ampC expression. RESULTS: Analysis of the ampC promoter region of E. coli N99-0001 revealed a T-->A mutation at -32, a C-->A mutation at -11, an insertion of a T between -20 and -21, and a 28 bp deletion including the entire attenuator. RT-PCR showed that ampC was expressed 140-fold higher in E. coli N99-0001 than in E. coli ATCC 25922. CONCLUSIONS: Cefoxitin resistance in E. coli N99-0001 was due to overexpression of ampC caused by an increase in promoter strength.
Amino Acid Sequence↗
Molecular characterization of cefoxitin-resistant Escherichia coli from Canadian hospitals.
A study designed to gain baseline information on strains of Escherichia coli displaying resistance to cefoxitin in Canada is described. A total of 29,323 E. coli isolates were screened at 12 participating hospital sites as part of an extended-spectrum beta-lactamase surveillance initiative. A total of 411 clinically significant, nonrepeat isolates displaying reduced susceptibilities to the NCCLS-recommended beta-lactams were submitted to a central laboratory over a 1-year period ending on 30 September 2000. Two hundred thirty-two isolates were identified as resistant to cefoxitin. All cefoxitin-resistant strains were subtyped by pulsed-field gel electrophoresis, and of these, 182 strains revealed a unique fingerprint and 1 strain was untypeable. PCR and sequence analysis of the ampC promoter region revealed 51 different promoter or attenuator variants and 14 wild-type promoters. Three promoter regions were interrupted by insertion elements, two contained IS10 elements, and one contained an IS911 variant. PCR and sequence analysis for the detection of acquired AmpC resistance (by the acquisition of ACT-1/MIR-1, CMY-2, or FOX) revealed that 25 strains contained CMY-2, including 7 of the strains found to have wild-type promoters. The considerable genetic variability in both the strain fingerprint and the promoter region suggests that AmpC-type resistance may emerge spontaneously by mutation of sensitive strains rather than by the spread of strains or plasmids in the hospital setting.
Anti-Bacterial Agents↗
Identification of a progenitor of the CTX-M-9 group of extended-spectrum beta-lactamases from Kluyvera georgiana isolated in Guyana.
Chromosomal beta-lactamase genes (bla(KLUY)) from six Kluyvera georgiana strains isolated in Guyana were cloned and expressed in Escherichia coli. KLUY-1 exhibited 100% amino acid identity with the extended-spectrum beta-lactamase CTX-M-14. We also show that a 2.7-kb Kluyvera chromosomal region exhibits 99% nucleotide identity to a portion of In60 that includes bla(CTX-M-9).
Amino Acid Sequence↗
Enterococcus faecium N03-0072 carries a new VanD-type vancomycin resistance determinant: characterization of the VanD5 operon.
OBJECTIVES: To genotypically characterize the vancomycin resistance mechanism of Enterococcus faecium N03-0072, which was negative by PCR for the currently known van genotypes. METHODS: PCR was used to amplify the entire vancomycin resistance operon and the complete nucleotide sequence was determined by dideoxy cycle sequencing. RESULTS: Analysis revealed a VanD-type operon with 94% nucleotide identity to the VanD4 operon and 90% nucleotide identity to the VanD1/D3 operons. A set of universal primers was designed in order to identify all current vanD variants by PCR. CONCLUSIONS: E. faecium N03-0072 carries a new VanD-type operon, designated VanD5.
Bacterial Proteins↗
Characterization of a Salmonella enterica serovar Agona strain harbouring a class 1 integron containing novel OXA-type beta-lactamase (blaOXA-53) and 6'-N-aminoglycoside acetyltransferase genes [aac(6')-I30].
OBJECTIVE: To characterize by molecular methods a multidrug-resistant Salmonella enterica serovar Agona (S. enterica Agona) isolated from a hospitalized patient in Rio de Janeiro, Brazil. METHODS: The S. enterica Agona strain was screened by PCR and DNA sequencing for TEM, SHV and CTX-M-type beta-lactamase genes, tet(A), (B), (C) and (D) tetracycline resistance genes, chloramphenicol resistance genes and class 1 integrons. Plasmid characterization was carried out by PCR and Southern hybridization analysis. PCR and PFGE were used to characterize nine other S. enterica Agona strains collected from hospitals in Rio de Janeiro. RESULTS: The study strain was found to harbour a 105 kb plasmid, which contained catA1, bla(TEM-1), a class 1 integron with two novel genes labelled bla(OXA-53) and aac(6')-I30, respectively, and an additional unidentified aminoglycoside resistance gene. A second 53 kb plasmid from the same strain contained tet(D) and bla(SHV-5). OXA-53 was shown to provide reduced susceptibility to ceftazidime, and its activity was inhibited in the presence of clavulanic acid. PFGE analysis of the nine other S. enterica Agona strains revealed two clusters of related strains (78% similarity), and PCR analysis showed that all strains contained the novel integron. CONCLUSION: An S. enterica Agona strain was found to harbour three plasmid-encoded beta-lactamases, one (OXA-53) on a novel class 1 integron that also contains a new aminoglycoside resistance gene, aac(6')-I30. The multidrug resistance plasmids appear to have disseminated to other city hospitals via other S. enterica Agona strains.
Acetyltransferases↗
Complete nucleotide sequence of a 92-kilobase plasmid harboring the CTX-M-15 extended-spectrum beta-lactamase involved in an outbreak in long-term-care facilities in Toronto, Canada.
A major outbreak involving an Escherichia coli strain that was resistant to expanded-spectrum cephalosporins occurred in Toronto and surrounding regions in 2000 to 2002. We report the complete sequence of a plasmid, pC15-1a, that was found associated with the outbreak strain. Plasmid pC15-1a is a circular molecule of 92,353 bp consisting of two distinct regions. The first is a 64-kb region that is essentially homologous to the non-R-determinant region of plasmid R100 except for several point mutations, a few small insertions and deletions, and the absence of Tn10. The second is a 28.4-kb multidrug resistance region (MDR) that has replaced the R-determinant region of the R100 progenitor and consists mostly of transposons or partial transposons and five copies of the insertion element IS26. All drug resistance genes found in pC15-1a, including the beta-lactamase genes bla(CTX-M-15), bla(OXA-1), and bla(TEM-1), the tetracycline resistance gene tetA, and aminoglycoside resistance genes aac(6')-Ib and aac(3)-II, are located in the MDR. The bla(CTX-M-15) gene was found downstream of ISEcp1as part of a transposition unit, as determined from the surrounding sequence. Examination of the plasmids from CTX-M-15-harboring strains isolated from hospitals across Canada showed that pC15-1a was found in several strains isolated from a site in western Canada. Comparison of pC15-1a and pCTX15, found in an E. coli strain isolated in India in 1999, revealed that the plasmids had several features in common, including an R100 backbone and several of the resistance genes, including bla(CTX-M-15), bla(TEM-1), bla(OXA-1), tetA, and aac(6')-Ib.
Base Sequence↗
Molecular and kinetic comparison of the novel extended-spectrum beta-lactamases CTX-M-25 and CTX-M-26.
CTX-M-25 is a novel extended-spectrum beta-lactamase isolated from a single Canadian Escherichia coli isolate. Susceptibility testing demonstrated that this enzyme confers resistance to both cefotaxime and ceftazidime, but the level of resistance was reduced with the addition of beta-lactamase inhibitors. The bla(CTX-M-25) gene was detected on a 111-kb plasmid. It is a member of the CTX-M-8 group and has the closest amino acid identity (99%; three amino acid substitutions) with CTX-M-26. The bla(CTX-M-26) gene was detected on a 100-kb plasmid isolated from a Klebsiella pneumoniae strain from the United Kingdom, and plasmid profiling revealed that it showed some homology to the bla(CTX-M-25)-harboring plasmid. Both CTX-M genes were located downstream of ISEcp1, although the copy upstream of bla(CTX-M-25) was disrupted by IS50-A. Comparative kinetic studies of recombinant CTX-M-25 and CTX-M-26 enzymes showed that CTX-M-25 has a higher level of ceftazidime hydrolysis (kcat values, 33 and 0.005 s(-1) for CTX-M-25 and CTX-M-26, respectively).
Amino Acid Sequence↗
Unilateral lower extremity edema in May-Thurner syndrome.
Deep venous thrombosis (DVT) tops the differential diagnosis list for unilateral lower extremity edema, but another entity could imitate or even cause a DVT. May-Thurner syndrome is caused by compression of the left common iliac vein by the overlying right iliac artery, resulting in impeded venous blood flow from the left lower extremity. The left leg becomes edematous, causing discomfort and concern. Early recognition of May-Thurner could prevent a DVT and provide symptomatic relief.
Constriction, Pathologic↗