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Biomedical subjects

J Heritage

Publications and source records attributed to J Heritage.

At least 19 recordsLinked to original sources
PubMed1992

Transposition of the gene encoding a TEM-12 extended-spectrum beta-lactamase.

An isolate of Klebsiella oxytoca from the blood culture of a child with leukemia was found to produce two beta-lactamases, at least one of which conferred resistance to ceftazidime. Genes encoding both enzymes were located on a single self-transmissible 100-kb plasmid, pOZ201. This plasmid was introduced into Escherichia coli UB5201 (pACYC184), and the gene encoding one beta-lactamase was transposed onto plasmid pACYC184 by exploiting a gene dosage effect. The transposable gene was found to encode a TEM-12 enzyme as determined by nucleotide sequencing. This gene was subsequently transposed onto plasmid pUB307. The transposable element encoding the TEM-12 enzyme has been designated Tn841. Both plasmids pACYC184::Tn841 and pUB307::Tn841 were shown to encode a beta-lactamase with the same isoelectric point and substrate profile as the TEM-12 beta-lactamase. Transposon Tn841, at approximately 7 kb, is larger than TnA (4.8 kb) and transposes at a lower frequency. Although it produced a resolvase which can complement the resolvase of Tn3, its transposase function was not able to complement the transposition of a TnA element which lacked transposase. The occurrence of a gene encoding an extended-spectrum beta-lactamase on a transposable element in a clinically significant bacterium is potentially a cause for concern for the spread of resistance to the extended-spectrum cephalosporins.

Base Sequence↗
PubMed1991

Molecular evolution of tetracycline-resistance plasmids carrying TetM found in Neisseria gonorrhoeae from different countries.

High level tetracycline resistant strains of Neisseria gonorrhoeae (TRNG) have been shown to carry a 40.6 kb (25.2 MDa) conjugative plasmid with a Class M tetracycline resistance determinant. Restriction endonuclease analysis mapping showed that there were at least two different TRNG plasmid types which were found in geographically distinct locations. The physical maps of these two plasmids were compared to a gonococcal conjugative plasmid which did not encode tetracycline resistance. The plasmid type which is endemic in the Netherlands was found to be closely related to the gonococcal conjugative plasmid, which supports the established hypothesis that the 40.6 kb plasmid has evolved by transposition of the TetM determinant into the conjugative plasmid. The plasmid found in the United States has either evolved by substantial divergent evolution or it results from a different transposition event. In the UK there have been isolations of TRNGs carrying either of the two plasmid types reflecting a flow of people both across the Atlantic and in Europe. It is possible that further TetM-containing plasmids will be found in N. gonorrhoeae paralleling the family of TEM beta-lactamase encoding plasmids already described.

Bacterial Proteins↗
PubMed1990

The 25.2 MDa tetracycline-resistance plasmid is not derived from the 24.5 MDa conjugative plasmid of Neisseria gonorrhoeae.

High-level tetracycline resistance in strains of Neisseria gonorrhoeae is due to the presence of a 25.2 MDa conjugative plasmid. This plasmid has been shown to carry the streptococcal tetM determinant, and has been thought to have evolved from the 24.5 MDa conjugative plasmid found in N. gonorrhoeae. We have derived a physical map of the 25.2 MDa plasmid pUS100 using seven restriction endonucleases. Comparison of the physical map with the previously published physical map of the conjugative plasmid pLE2451 shows there to be no obvious similarity between the two plasmids. The location of the tetM determinant has been established, by Southern hybridization, confirming the restriction endonuclease map. This has also provided evidence that the transposition functions normally associated with the tetM determinant have been lost.

Conjugation, Genetic↗
PubMed1990

Novel beta-lactamase from Capnocytophaga sp.

A novel beta-lactamase activity which confers resistance to expanded-spectrum cephalosporins and penicillins has been found in strain IC 5/21 of Capnocytophaga spp. Enzyme activity migrated at a molecular size of 38,000 daltons and at an isoelectric point of 3.6, with a minor band at 4.1. Kinetic studies suggested that it belonged to Richmond and Sykes beta-lactamase class 1c. Isoelectric focusing could be achieved only if a nonionic detergent was added to the gel, suggesting the presence of a hydrophobic enzyme akin to a membrane-bound beta-lactamase of gram-positive bacteria. The location of the gene coding for this beta-lactamase is not yet known.

Anti-Bacterial Agents↗
PubMed1990

Accountancy, teaching methods, sex, and American College Test scores.

This study examines the significance of sex, methodology, academic preparation, and age as related to development of judgmental and problem-solving skills. Sex, American College Test (ACT) Mathematics scores, Composite ACT scores, grades in course work, grade point average (GPA), and age were used in studying the effects of teaching method on 96 students' ability to analyze data in financial statements. Results reflect positively on accounting students compared to the general college population and the women students in particular.

Accounting↗
PubMed1988

Selection of resistance to gentamicin and netilmicin in the faecal flora following prophylaxis for colo-rectal surgery.

The selection of aminoglycoside-resistant bowel flora, following the administration of either gentamicin or netilmicin in combination with metronidazole for prophylaxis, during colo-rectal surgery in 88 patients has been examined. Both antibiotic regimens resulted in the selection of an aminoglycoside-resistant flora in a total of 57 (65%) of patients: in half of the patients there was a net gain in the aminoglycoside-resistant flora, and in 13 (15%) one aminoglycoside-resistant strain present prior to prophylaxis was displaced by another following operation. Three patients (3%) lost aminoglycoside-resistant strains after prophylaxis. Most of the resistant organisms selected were considered to be of little importance as potential pathogens, at least in the short term. In only a small minority (5%) of patients were aminoglycoside-resistant enterobacteria isolated. Aminoglycoside-resistant Staphylococcus aureus was not isolated. Of the resistant enterobacteria, only one strain, an isolate of Enterobacter cloacae selected in a patient receiving gentamicin, carried a resistance determinant which was self-transmissible to Escherichia coli.

Clinical Trials as Topic↗
PubMed1987

beta-Lactamase production by intestinal spirochaetes.

beta-Lactamase production was demonstrated in four of nineteen strains of intestinal spirochaetes isolated from human subjects. The enzyme was preferentially active against penicillins and was inhibited by clavulanic acid; it was membrane bound and non-inducible. No plasmids were detected in the intestinal spirochaetes and the beta-lactamase-production characteristic was not transferable to non-producing strains.

Humans↗
PubMed1986

Probable chromosomal mutation to resistance to all aminoglycosides in Staphylococcus aureus selected by the therapeutic use of gentamicin: a preliminary report.

A patient suffering from burns was treated with gentamicin: subsequently, a 'methicillin-resistant' strain of Staphylococcus aureus (B27), was isolated which was highly resistant to this antibiotic and all other aminoglycosides. In all other respects this isolate resembled the gentamicin-sensitive 'methicillin-resistant' S. aureus prevalent on the Yorkshire Regional Burns Unit. Subsequently, fusidic acid treatment was substituted for gentamicin therapy, and a fusidic acid-resistant variant was isolated from the same patient. This article reports a preliminary characterization of these isolates.

Adult↗
PubMed1986

An ultra-rapid method for the study of antibiotic resistance plasmids.

A rapid method of isolating plasmid DNA has been developed from that of Birnboim & Doly (1979). This method allows large numbers of strains to be examined, and can be employed to isolate DNA from members of the Enterobacteriaceae, Pseudomonas aeruginosa, Staphylococcus aureus, (including methicillin-resistant strains) and coagulase-negative staphylococci. Plasmids of widely differing sizes are amenable to isolation by this technique, which yields DNA of sufficient purity to allow restriction endonuclease and homoduplex analysis.

Bacteria↗
PubMed1986

Evolution of R plasmids by replicon fusion.

The occurrence of plasmid-plasmid fusions in nature and their possible influence on the spread of bacterial drug resistance is considered. Three ways in which replicon fusions can be formed are described; specifically fusions mediated by IS elements, "one-ended transposition" systems derived from Tn3 and like transposons, and pUB2380, a prototype for a new type of transposition. Non-transposition based systems which mediate replicon fusion are also briefly considered.

Biological Evolution↗
PubMed1985

Plasmid fusions mediated by one end of TnA.

We have observed plasmid fusions in a recA background mediated by a single end of TnA. These occur when transposase is provided either in cis or in trans. Insertions of the plasmid carrying the TnA inverted repeat sequence occur at many sites in the target plasmid. The point of fusion on the plasmid carrying TnA sequences always appears to be located in the region which carries the TnA inverted repeat sequence. In contrast to the transposition of an intact TnA element, plasmid fusions mediated by one end of TnA are very rare events. The implications of our results for models of transposition are discussed.

Chromosome Mapping↗