Search PubMed⌕ Search

Biomedical subjects

T H Pennington

Publications and source records attributed to T H Pennington.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1996

Molecular epidemiology of Escherichia coli O157:H7 by pulsed-field gel electrophoresis and comparison with that by bacteriophage typing.

One hundred twenty-four Escherichia coli O157:H7 isolates were characterized by pulse-field gel electrophoresis, bacteriophage typing, and PCR of verotoxin genes. Diversity indices obtained--0.786 for phage types and 0.987 for pulsed-field gel electrophoresis types--demonstrated that phage typing falls below the critical value (0.9) required for confident interpretation of results.

Animals↗
PubMed1995

Incidence and spread of Haemophilus influenzae on an Antarctic base determined using the polymerase chain reaction.

A PCR-based method of detecting Haemophilus influenzae in cultures inoculated from throat swabs was evaluated using samples from groups of laboratory staff and medical students and then applied to samples originating from the closed human community of an Antarctic research station. Suitable PCR primers to an H. influenzae gene (ompP2) were used to amplify the gene from DNA preparations made from mixed growth on chocolate agar with added vancomycin. PCR product was reamplified and subjected to restriction endonuclease digestion to allow temporal and spatial mapping of strains over an 8-month period. Eleven different strains of H. influenzae were detected. One particular strain was detected in a third of the base members.

Adult↗
PubMed1995

Population genetics of Mycobacterium tuberculosis complex in Scotland analysed by pulsed-field gel electrophoresis.

The results of typing of 121 strains in the Mycobacterium tuberculosis complex by PFGE are presented. Every isolate from patients in Scotland over a 3-month period for M. tuberculosis and for 1 year for M. bovis were included along with several laboratory strains including those of BCG. The PFGE results suggest that the population structure of all the strains in this complex is distinctly simple with limited genetic diversity and also suggest that M. bovis is not a distinct species.

DNA Fingerprinting↗
PubMed1995

Allelic variation in the Helicobacter pylori flagellin genes flaA and flaB: its consequences for strain typing schemes and population structure.

Extensive DNA sequence diversity was noted in Helicobacter pylori flagellin genes flaA and flaB. PCR amplified sequences from 49 isolates were digested with AluI, HindIII, MboI or MspI, the resultant patterns were compared between the different isolates and these used to differentiate the isolates from each other. Evidence that the extensive diversity that was found in these genes is the result of reassortment of sequences between strains in the bacterial population is presented, such that a comparatively small number of individual sequence mutations can recombine together in random combinations to form a greater number of distinct alleles. Geographical differences in the predominant patterns in the flaA alleles were also observed and could reflect regional differences either in the human host population or in the bacterial population. In view of the genetic complexity of this species, molecular typing schemes designed to identify related strains may falsely associate strains if the methods do not characterize sufficient genetic sites to exclude chance associations of genetic markers in strains which are actually not closely related to each other.

Alleles↗
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↗
PubMed1995

Antimicrobial susceptibility of penicillin-sensitive and penicillin-resistant meningococci.

Ceftriaxone showed high in-vitro activity against 119 penicillin-sensitive, penicillin-resistant and rifampicin-resistant UK isolates of meningococci. Unlike ciprofloxacin and minocycline, ceftriaxone is suitable for use in young children or in pregnancy and should be considered for therapy or prophylaxis in an outbreak of meningococcal disease. The E test gave results comparable to those given by broth microdilution method in the determination of meningococcal susceptibility to antimicrobials. It is convenient for use in small laboratories and can be used to determine antimicrobial subgroups of meningococci.

Anti-Bacterial Agents↗
PubMed1995

Differences exist in the immunoblotting profiles of cyst and trophozoite antigens of Pneumocystis carinii.

The antigenic profiles of Pneumocystis carinii trophozoites and cysts were compared by immunoblotting with hyperimmune rat sera against cyst and trophozoite antigens. Strong bands corresponding to proteins of 50-60 kDa and 104 kDa were demonstrated in cyst and trophozoite antigens by all antisera. Additional prominent proteins of 81 and 63 kDa and less prominent proteins of 88, 73, 69 and 37 kDa were found only in trophozoite antigen. The latter proteins were recognised by anti-trophozoite and anti-cyst antisera but the 81- and 63-kDa proteins were associated specifically with trophozoites. With cyst-rich antigen, antibodies to the 50-60-kDa protein were detected in only two of 14 sera from P. carinii pneumonia (PCP)-positive rats. With trophozoite-rich antigen, 11 of 24 rats with PCP and one of 18 PCP-negative animals had antibodies to both the 50-60 kDa and 104-kDa antigens. Antibodies to the 81- or 63-kDa antigens were demonstrated in 15 of 24 PCP-positive animals and none of the PCP-negative animals. The use of trophozoites rather than cysts increased the sensitivity of immunoblotting. As trophozoites predominate in PCP, antibody to trophozoite-specific antigens rather than common cyst and trophozoite antigens is likely to be a more useful marker of current infection.

Animals↗
PubMed1995

The use of a nested polymerase chain reaction for detecting Pneumocystis carinii from lung and blood in rat and human infection.

A nested polymerase chain reaction (PCR) assay was developed to detect both rat- and human-derived Pneumocystis carinii DNA. The nested PCR product was 125 bp long and was representative of part of the gene coding for the large subunit of mitochondrial ribosomal RNA. Twenty serial blood samples and 24 tissues from six immunosuppressed Sprague-Dawley rats were examined by nested PCR. All lung samples were positive by PCR and Toluidine blue O staining. Buffy coat samples and all the other tissues were PCR-negative during up to 6 weeks of immunosuppression. Thirty-five clinical bronchoalveolar lavage, induced sputum or tracheal aspirate samples from human patients were tested. Twelve of 35 were positive by both PCR and indirect fluorescence assay (IFA) and 19 of 35 were both PCR- and IFA-negative. Four of 35 were IFA-negative but PCR-positive and there were good responses in these patients to specific therapy, indicating that PCR may be more useful than IFA in clinical samples. P. carinii DNA was not detected in three blood samples. The nested PCR is a sensitive and specific DNA amplification method suitable for the routine diagnosis of P. carinii in human respiratory samples.

Animals↗
PubMed1995

Epidemiological evaluation of Neisseria meningitidis serogroup B by pulsed-field gel electrophoresis.

Genomic DNA from 25 strains of serogroup B Neisseria meningitidis was subjected to pulsed-field gel electrophoresis (PFGE) after digestion with Spe I. N. meningitidis genomic DNA displayed considerable diversity. The diversity we observed among these strains was stable and included isolates from an outbreak that were phenotypically identical. This confirms the value of macrorestriction profiling and PFGE in providing epidemiologically stable strain markers for typing meningococci.

DNA, Bacterial↗
PubMed1995

Specificity and usefulness of an IgE immunosorbent agglutination assay for toxoplasmosis.

AIMS: To develop an immunosorbent agglutination assay for the detection of Toxoplasma gondii IgE antibodies (IgE-ISAGA); to assess its specificity; and to determine the role of specific IgE in the diagnosis of current toxoplasma infection. METHODS: Rabbit antihuman IgE capture antibody was adsorbed onto microtitre plates and formaldehyde fixed tachyzoites were used to identify specific antibody. Specificity was assessed in 513 serum samples (blood donor, potentially interfering and difficult, elevated and low total IgE and myeloma). Serum samples (n = 108) from 65 patients with documented toxoplasmosis were tested, as were 26 serum samples from nine pregnant women positive for specific IgM and 30 from 20 HIV positive patients. RESULTS: IgE-ISAGA was highly specific with only three of 513 (0.58%) positive reactions amongst the control groups, one of which (0.19%) was regarded as a false positive. Elevated total IgE did not influence specific IgE results nor did the presence of abnormal immunoglobulin concentrations. Sixty (92.3%) patients with toxoplasma associated lymphadenopathy had specific IgE in one or more samples. Positive or borderline results were obtained in 68 of 77 (88.3%) serum samples taken up to four months after onset and were also detected for up to 11 months in 21 of 31 (67.7%) sera. Of the nine pregnant women with detectable specific IgM, specific IgE was absent in five (12 specimens). Specific IgE was also detected in 10 of 30 (33.3%) serum samples from the 20 HIV positive patients, which was similar to the number with specific IgM. Neither the specific IgE nor IgM tests could distinguish symptomatic from asymptomatic HIV positive patients. CONCLUSIONS: IgE-ISAGA is sensitive, specific, and easy to perform. Although results suggest that specific IgE may be less helpful than previously claimed, specific IgE has a useful role in the diagnosis of current toxoplasma infection when used in conjunction with other tests.

AIDS-Related Opportunistic Infections↗
PubMed1995

The role of a nested polymerase chain reaction in the diagnosis of Pneumocystis carinii pneumonia.

Aim-To compare the techniques and results of a nested PCR and an immunofluorescence assay (IFA) for the detection of Pneumocystis carinii infection; to consider the role of the nested PCR in the diagnosis of P carinii pneumonia (PCP).Methods-Serial dilutions of two known P carinii positive samples were tested by IFA and PCR to determine their relative sensitivities. Seventy eight respiratory samples (15 from 11 patients with HIV infection/acquired immunodeficiency syndrome (AIDS) and 63 from 42 patients with other forms of immunodeficiency) were tested using both assays, and the costs and technical requirements of each assay were assessed.Results-The PCR had a greater relative sensitivity over the IFA of 2 x 10(1) to 2 x 10(3) fold in a postmortem lung sample and 2 x 10(5) to 2 x 10(6) fold in a bronchoalveolar lavage sample from a patient with PCP. P carinii was detected in all 15 samples from the patients with HIV/AIDS by both IFA and PCR. Of the 63 samples from the patients with immunodeficiencies other than HIV/AIDS, the PCR was more sensitive than IFA.Conclusions-The nested PCR is a more sensitive assay than the IFA. It may be useful in the diagnosis of PCP in patients with immunodeficiencies other than HIV/AIDS. Similarly, PCR may be of benefit for this patient group as less invasive specimens are needed. PCR has an increasing role to play in the diagnosis of PCP in the routine laboratory.

Journal Article↗