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Biomedical subjects

P E Carter

Publications and source records attributed to P E Carter.

At least 19 recordsLinked to original sources
PubMed2003

Coagulase gemne variants associated with distinct populations of Staphylococcus aureus.

An identifying characteristic of Staphylococcus aureus is the production of staphylocoagulase (coagulase). The aim of this study was to determine the clonal distribution of coagulase gene (coa) variants within populations of S. aureus defined by multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE), and protein A variation. The N-terminal region of the coa gene from 43 methicillin-susceptible (MSSA) and 252 methicillin-resistant (MRSA) S. aureus human isolates and 9 animal S. aureus isolates was amplified and digested with HinfI. Twelve types were identified amongst the MSSA isolates and the majority (93%) of MRSA isolates were assigned to 5 of the 12 types. MLST and PFGE analysis identified epidemic populations of MRSA and each epidemic population was characterized by a different coagulase type. Nine of the 12 MLST-defined clonal complex ancestral genotypes recently described each carried a different coagulase type suggesting that coagulase evolution and the evolution of the clonal complexes are intimately related.

Amino Acid Sequence↗
PubMed2000

Molecular typing of Toxoplasma gondii strains by GRA6 gene sequence analysis.

The utility of sequence polymorphisms in the dense granule antigen GRA6 gene as typing markers for Toxoplasma gondii was investigated. The coding region of GRA6 was amplified, sequenced and compared for 30 Toxoplasma strains from eight different zymodemes (Z1-Z8). Sequence alignment identified nucleotide polymorphisms at 24 positions out of 690 bp, which correlated with murine-virulence. Types I, II, and III could be distinguished from each other on the basis of three, 10, and six variable positions, respectively. Two deletions of 15 bp and 3 bp existed in the avirulent (type II) strains. With one exception, all polymorphic positions resulted in amino acid substitutions, and the two gaps of 15 bp and 3 bp caused the deletion of six amino acids in type II strains. Intra-specific polymorphisms were also found in the virulent group. A high degree of sequence polymorphism correlating with the phenotypes of T. gondii strains points to the GRA6 gene being a good marker for strain characterisation and typing of the isolates of this apicomplexan. The large variety of amino acid changes supports the view that the GRA6 protein plays an important role in the antigenicity and pathogenicity of T. gondii. The existence of polymorphic restriction sites for endonuclease MseI was used to develop a PCR-RFLP method which could simply differentiate the three different groups (types I, II, III) of T. gondii.

Animals↗
PubMed2000

Characterization of a recurrent clonal type of Escherichia coli O157:H7 causing major outbreaks of infection in Scotland.

A particular recurrent clonal type of Escherichia coli O157 has been isolated from multiple clinical, veterinary, food, and environmental sources throughout Scotland since 1989. Significant genotypic variation was detected among isolates from distinct outbreaks, with the presence or absence of single fragments being sufficient to delineate outbreak groups within the clonal type.

Bacterial Typing Techniques↗
PubMed2000

Intergenic spacer (IGS) polymorphism: a new genetic marker for differentiation of Toxoplasma gondii strains and Neospora caninum.

The region between the 28S and 18S rRNA genes, including the intergenic spacer (IGS) region and the 5S rRNA gene, from 32 strains of Toxoplasma gondii and the NC1 strain of Neospora caninum was amplified and used for DNA sequencing and/or restriction fragment length polymorphism (RFLP) analysis. The 5S rDNA sequences from 20 strains of T. gondii were identical. The IGS region between the 5S and 18S rRNA genes (nontranscribed spacer 2 or NTS 2) showed 10 nucleotide variations. Six of the 10 variant positions correlated with the murine virulence of the strains. Intraspecific polymorphisms distinguished the virulent strains of zymodemes 5, 6, and 8 from other virulent strains (in zymodeme 1). RFLP methods (IGS-RFLP) were developed and used to characterize the virulent and avirulent patterns among 29 T. gondii strains. Sequence diversity of 19.8% was found between T. gondii and N. caninum when comparing a region of 919 bp at the 3' end of NTS 2. The sequence variation in ribosomal IGS could therefore be a useful marker for Toxoplasma strain identification and for distinguishing N. caninum from T. gondii.

Animals↗
PubMed1999

Molecular epidemiological investigation of an outbreak of Campylobacter jejuni identifies a dominant clonal line within Scottish serotype HS55 populations.

Three molecular typing methods, pulsed-field gel electrophoresis (PFGE), ribotyping, and flagellin (flaA) gene typing, were used to discriminate within a group of 28 Campylobacter jejuni, heat-stable serotype 55 (HS55) isolates derived from cases of campylobacter enteritis occurring throughout Scotland, including 9 isolates associated with an outbreak. PFGE was found to be most discriminatory, identifying 6 distinct profiles, followed by ribotyping (5 profiles), and then flagellin gene typing (4 profiles). The coincidence of all three genotypic markers identified a dominant clonal line within the HS55 group, accounting for each of the outbreak strains, and for 9 of the 19 sporadic strains. A second, closely related, clonal line accounted for a further 5 of the sporadic strains, and also included the HS55 reference strain. Identification and monitoring of such clonal lines should facilitate more effective future epidemiological surveillance of C. jejuni.

Campylobacter Infections↗
PubMed1998

The detection of penicillin insensitivity in Neisseria meningitidis by polymerase chain reaction.

Strains of penicillin-sensitive and -insensitive Neisseria meningitidis were examined using a range of polymerase chain reaction (PCR) primers directed at the meningococcal penicillin-binding protein 2 gene. DNA from isolates whose penicillin MIC was <0.2 mg/L yielded a product of the expected size with all the primers, but many amplification patterns were seen with DNA from isolates whose MIC was above this level. All strains whose MIC was >0.25 mg/L failed to produce a product of the expected size with at least one of the primers used. The changes seen in penicillin-insensitive strains were consistent with horizontal gene transfer from Neisseria flavescens in some isolates, although the source for others remains unknown. PCR-based methods for the detection of antibiotic resistance are becoming increasingly important with the expanding use of molecular techniques for bacteriological diagnosis.

Bacterial Proteins↗
PubMed1998

The TATA-binding protein (TBP) from the human fungal pathogen Candida albicans can complement defects in human and yeast TBPs.

Candida albicans is the major fungal pathogen in humans, yet little is known about transcriptional regulation in this organism. Therefore, we have isolated, characterized, and expressed the C. albicans TATA-binding protein (TBP) gene (TBP1), because this general transcription initiation factor plays a key role in the activation and regulation of eukaryotic promoters. Southern and Northern blot analyses suggest that a single C. albicans TBP1 locus is expressed at similar levels in the yeast and hyphal forms of this fungus. The TBP1 open reading frame is 716 bp long and encodes a functional TBP of 27 kDa. C. albicans TBP is capable of binding specifically to a TATA box in vitro, substituting for the human TBP to activate basal transcription in vitro, and suppressing the lethal delta spt15 mutation in Saccharomyces cerevisiae. The predicted amino acid sequences of TBPs from C. albicans and other organisms reveal a striking pattern of C-terminal conservation and N-terminal variability: the C-terminal DNA-binding domain displays at least 80% amino acid sequence identity to TBPs from fungi, flies, nematodes, slime molds, plants, and humans. Sequence differences between human and fungal TPBs in the DNA-binding domain may represent potential targets for antifungal therapy.

Amino Acid Sequence↗
PubMed1997

Distribution and characterization of mosquitocidal toxin genes in some strains of Bacillus sphaericus.

The binary toxin of Bacillus sphaericus strains forms a crystal in sporulating cells, while the mosquitocidal toxin is located in the cytoplasm of vegetative cells. The distribution of binary toxin (btx) and mosquitocidal toxin (mtx) genes in 53 strains of B. sphaericus was determined by hybridization of specific gene probes to chromosomal DNA in Southern blots. btx genes were found in all strains of serotype 5a5b examined and in some strains of serotypes 1a, 3, 6, 25, and 48, while mtx genes were detected in strains of serotypes 1a, 2a2b, 5a5b, 6, 9a9c, 25, and 48. Serotype 26a26b strains lacked both toxin genes, as did some strains of serotypes 2a2b, 3, 6, and 48. Partial DNA sequences of btx genes from five strains, together with published sequences, revealed four types of toxin among mosquitocidal B. sphaericus strains. most of the 42-kDa toxin gene of btx was identical in strains from serotypes 1a, 3, 6, and 48, and the gene is here classified as a type 1 btx gene. A serotype 3 strain isolated in Singapore possessed a unique 42-kDa toxin gene, here designated type 4; while the btx genes from strains of serotypes 5a5b and 25 are referred to as types 2 and 3, respectively.

Bacillus↗
PubMed1997

Evidence for recombination in the flagellin locus of Campylobacter jejuni: implications for the flagellin gene typing scheme.

The flagellin subunit of the flagellar filament in Campylobacter jejuni is encoded by two highly homologous tandem genes, flaA and flaB. The flaA gene was sequenced in 18 strains of C. jejuni, including isolates from three outbreak groups. Sequences obtained were compared with flaA sequences available in the GenBank database, and all were analyzed for mosaic gene structure by using recently described statistical tests for detecting gene conversion among aligned sets of sequences. Strong evidence was found supporting recombination between flaA genes of different strains (i.e., intergenomic recombination). Intragenomic recombination between the flaA and flaB genes of C. jejuni TGH9011 was also demonstrated. Both mechanisms of recombination may act as a potential means by which pathogenic strains can generate increased antigenic diversity, so allowing them to escape the immunological responses of the host. Furthermore, demonstration of recombination within and between flagellin loci of natural strains suggests that flagellin gene typing (restriction fragment length polymorphism analysis of PCR-amplified flagellin genes) cannot be considered a stable method for long-term monitoring of pathogenic Campylobacter populations.

Base Sequence↗
PubMed1996

Rifampin resistance in Neisseria meningitidis due to alterations in membrane permeability.

Rifampin-resistant (Rifr) Neisseria meningitidis strains are known to have single point mutations in the central conserved regions of the rpoB gene. We have demonstrated two distinct resistance phenotypes in strains with identical mutations in this region, an intermediate level of resistance in Rifr clinical isolates and a high level of resistance in mutants selected in vitro. The possible role of membrane permeability in the latter was investigated by measuring MICs in the presence of Tween 80; values for high-level-resistance mutants were reduced to intermediate levels, whereas those for intermediate-level-resistance strains were unaffected. The highly resistant mutants were also found to have increased resistance to Triton X-100 and gentian violet. Sequencing of the meningococcal mtrR gene and its promoter region (which determine resistance to hydrophobic agents in Neisseria gonorrhoeae) from susceptible or intermediate strains and highly resistant mutants generated from them showed no mutation within this region. Two-dimensional gel electrophoresis of two parent and Rif mutant strains showed identical shifts in the pI of one protein, indicating that differences between the parent and the highly Rifr mutant are not confined to the rpoB gene. These results indicate that both permeability and rpoB mutations play a role in determining the resistance of N. meningitidis to rifampin.

Anti-Bacterial Agents↗
PubMed1996

Genetic heterogeneity of M type 3 group A streptococci causing severe infections in Tayside, Scotland.

To explain the worldwide increase in the frequency of severe infections by group A streptococci, molecular techniques are increasingly being employed to evaluate the genetic relationships of strains. We used restriction endonuclease analysis, pulsed-field gel electrophoresis (PFGE), the PCR, ribotyping, and DNA sequence analysis in a study of 13 group A streptococci isolated from a cluster of cases of serious infections over a 3-month period in Tayside, Scotland. Eight of the strains were M type 3; molecular characterization identified two subclones. The first, displaying PFGE profile 4, has been observed in Northern Scotland and has been circulating in New Zealand for over a decade. The second subclone has been documented only in the United Kingdom; it was first seen in 1993 in Scotland. Sequence analysis of emm-3 genes further differentiated the PFGE 4 subclone. DNA sequence analysis of virulence factors supports the suggestion that they may have recently been acquired by horizontal gene transfer.

Bacterial Typing Techniques↗
PubMed1995

Clonal structure of invasive Streptococcus pyogenes in Northern Scotland.

We have used molecular techniques to characterize 51 group A streptococci from Scotland and 17 'serious disease' isolates from other countries, in order to establish the clonal structure of invasive Streptococcus pyogenes strains circulating between 1986 and 1993. Strains were grouped by restriction endonuclease analysis, pulsed field gel electrophoresis and ribotyping patterns, and were examined for the presence of alleles of the speA gene by polymerase chain reaction and DNA sequence analysis. Serious and fatal infections in Scotland were caused by several clones. One clone (9 of 51 strains) was M type 1 and possessed the speA gene allele 2. This was the clone previously identified as causing severe infection in the USA. Another clone (5 of 51 strains) was M type 3 and had speA gene allele 3. In view of the clear association of more than one clone with severe, invasive and fatal infections, horizontal gene exchange between genotypes merits further investigation.

Base Sequence↗
PubMed1994

Phylogenetic relationships between some members of the genera Neisseria, Acinetobacter, Moraxella, and Kingella based on partial 16S ribosomal DNA sequence analysis.

We obtained 16S ribosomal DNA (rDNA) sequence data for strains belonging to 11 species of Proteobacteria, including the type strains of Kingella kingae, Neisseria lactamica, Neisseria meningitidis, Moraxella lacunata subsp. lacunata, [Neisseria] ovis, Moraxella catarrhalis, Moraxella osloensis, [Moraxella] phenylpyruvica, and Acinetobacter lwoffii, as well as strains of Neisseria subflava and Acinetobacter calcoaceticus. The data in a distance matrix constructed by comparing the sequences supported the proposal that the genera Acinetobacter and Moraxella and [N.] ovis should be excluded from the family Neisseriaceae. Our results are consistent with hybridization data which suggest that these excluded taxa should be part of a new family, the Moraxellaceae. The strains that we studied can be divided into the following five groups: (i) M. lacunata subsp. lacunata, [N.] ovis, and M. catarrhalis; (ii) M. osloensis; (iii) [M.] phenylpyruvica; (iv) A. calcoaceticus and A. lwoffii; and (v) N. meningitidis, N. subflava, N. lactamica, and K. kingae. We agree with the previous proposal that [N.] ovis should be renamed Moraxella ovis, as this organism is closely related to Moraxella species and not to Neisseria species. The generically misnamed taxon [M.] phenylpyruvica belongs to the proposed family Moraxellaceae, but it is sufficiently different to warrant exclusion from the genus Moraxella. Further work needs to be done to investigate genetically similar species, such as Psychrobacter immobilis, before the true generic position of this organism can be determined. Automated 16S rDNA sequencing with the PCR allows workers to accurately determine phylogenetic relationships between groups of organisms.(ABSTRACT TRUNCATED AT 250 WORDS)

Acinetobacter↗
PubMed1994

Comparison of IgG subclasses in foetal serum, maternal serum at delivery and milk in IgA-deficient and control women.

Immunoglobulin G subclass concentrations were measured in paired foetal (cord) and maternal serum specimens at delivery from 27 IgA-deficient (serum IgA < 0.01 g/l) and 15 control women. IgA-deficient women had significantly higher serum IgG1 and IgG3 concentrations than control women but 2 of the group had concomitant IgG2/IgG4 deficiency and a further 12 had low IgG4 concentrations (serum IgG4 < 0.025 g/l). Foetal serum also had significantly higher IgG1 concentrations than control foetal serum but lower IgG2 and IgG4 levels. Concentrations of IgG subclasses and IgM were measured in breast milk collected on the fifth day postpartum from 19 of these IgA-deficient and 18 control women. Between-group differences in IgG subclass levels resembled those in serum. Compared with serum, proportionally less IgG3 was present in milk in both groups although the contribution of IgG3 to total IgG was not less than that of IgG4. Slightly higher IgM was found in milk from the IgA-deficient mothers.

Case-Control Studies↗
PubMed1994

Molecular characterization of rifampin-resistant Neisseria meningitidis.

Primers were designed to amplify the rpoB gene of Neisseria meningitidis. The region of the gene amplified covered clusters I and II of the rifampin resistance (Rifr) mutation sites identified in Escherichia coli. DNAs from six Rifr isolates and 21 rifampin-susceptible isolates from the United Kingdom representing a number of serogroups were amplified and sequenced. All six Rifr isolates had identical DNA sequences and the same amino acid change, a His to an Asn change at position 35 (H35N). This His residue is equivalent to the His residue at position 526 in E. coli, one of the known Rifr mutation sites. DNAs from an additional six Rifr mutations generated in vitro were amplified and sequenced. Three had H35Y changes, one had an H35R change, one had an H35N change and one had an S40F change. The predominance of mutations at the His residue at position 35 in Rifr N. meningitidis isolates suggests that it plays a critical role in the selection of antibiotic-resistant variants. All six Rifr isolates belonged to the same clonal group when analyzed by restriction enzyme analysis and pulsed-field gel electrophoresis. These data suggest that a single clone of Rifr N. meningitidis is present and widespread throughout the United Kingdom.

Amino Acid Sequence↗
PubMed1993

Effects of high doses of inhaled corticosteroids on adrenal function in children with severe persistent asthma.

BACKGROUND: Childhood asthma generally responds well to inhaled corticosteroids within the dosage range recommended by the manufacturers, but it is sometimes necessary to use higher doses--that is, above 400 micrograms/day--a practice which has become more widespread recently. Whereas the lack of adrenal suppression in children given inhaled corticosteroids in normal doses is well documented, little is known about the effects of higher doses. METHODS: The effects on adrenal function of high dose (above 400 micrograms/day) inhaled corticosteroids were evaluated by measuring cortisol concentration in the morning and performing a short tetracosactrin test in 49 children taking budesonide (mean age 9.2 years (range 4 to 16 years) and 28 children taking beclomethasone dipropionate (10.2 years (5 to 13 years)). Twenty three non-asthmatic children (8.9 years (4.9 to 13 years)) who were under investigation for short stature served as controls for the study. RESULTS: Compared with controls mean basal cortisol concentration was lower in children taking budesonide and beclomethasone dipropionate (control 401 (26.8) nmol/l, budesonide 284 (22) nmol/l, beclomethasone dipropionate 279 (23.2) nmol/l). Sixteen of the 49 children taking budesonide had subnormal basal cortisol concentrations compared with seven of the 28 taking beclomethasone dipropionate. Mean stimulated cortisol concentrations were lower in children taking inhaled corticosteroids than in controls, with no difference between those taking budesonide or beclomethasone dipropionate. CONCLUSIONS: Adrenal suppression occurs in some children who are given inhaled corticosteroids in doses greater than 400 micrograms/day. It may therefore be advisable to try alternative treatments before such doses are used.

Administration, Inhalation↗
PubMed1993

IgG subclass concentrations and Gm allotypes in IgA-deficient and normal pregnant women.

IgG subclass concentrations were measured in the serum of 40 IgA-deficient (IgA concentration < 0.01 milligram) and 38 normal women in the second trimester of pregnancy. In the IgA-deficient group, 2 women were also deficient in IgG2 and IgG4, while a further 10 had very low concentrations of serum IgG4 only. These low IgG4 values were unrelated to the presence of anti-IgA antibodies. The incidence of low IgG4 values was significantly greater (p < 0.01) than in the control group where only 1 woman had low IgG4 and none had low IgG2. Mean values for total IgG, IgG1 and IgG3 were very significantly higher (p < 0.001) in the IgA-deficient group than in the control group. These differences were unrelated to Gm phenotype.

Female↗