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S H Gillespie

Publications and source records attributed to S H Gillespie.

At least 37 records · Page 2Linked to original sources
PubMed2000

Comparison of fitness of two isolates of Mycobacterium tuberculosis, one of which had developed multi-drug resistance during the course of treatment.

OBJECTIVES: We report the cases of two patients, brother and sister, both with pulmonary tuberculosis. Both patients complied poorly with treatment. One developed multi-drug resistant disease, whilst the other did not. We aimed to show that the two infecting strains were the same, and then to compare the fitness of the resistant strain to that of the sensitive strain. METHODS: The isolates were typed by RFLP. The fitness of the multi-drug resistant tuberculosis strain was determined by calculating the ratio of generation produced by the drug-resistant and a drug-susceptible strain in a mixed culture. The number of bacteria present in this broth culture was estimated using the Miles and Misra technique. The number of drug-resistant bacteria present was determined by inoculating aliquots of broth onto Middlebrook 7H10 agar with 5mg/l rifampicin. RESULTS: The infecting strain of Mycobacterium tuberculosis was shown to be the same on RFLP typing in both cases. It was found that the multi-drug resistant organism had decreased fitness compared to the sensitive organism. CONCLUSION: The decreased relative fitness of the resistant strain implies a physiologic cal cost for the development of drug resistance.

Antitubercular Agents↗
PubMed2000

Pathogenesis of pneumococcal infection.

The pathogenesis of pneumococcal infection is a complex interplay between pneumococcal virulence determinants and the host immune response. Molecular studies have considerably advanced our knowledge and understanding of the precise structures and functions of the different determinants and their pathogenic roles. This review describes the mechanisms by which pneumococci attach, invade, evade lung defences and cause severe disease. Better understanding of the critical steps in this complex process will enable more effective clinical intervention to be developed to reduce the mortality exacted by this versatile pathogen.

Animals↗
PubMed2000

Comparison of phenotypic and genotypic methods for pyrazinamide susceptibility testing with Mycobacterium tuberculosis.

Mycobacterium tuberculosis converts pyrazinamide to its active form by using the enzyme pyrazinamidase. This enzyme is coded for on the pncA gene, and mutations in the pncA gene result in absence of active enzyme, conferring resistance to the drug pyrazinamide. We investigated 27 strains of Mycobacterium tuberculosis suspected of being multidrug resistant. Each isolate was tested for susceptibility to pyrazinamide by the BACTEC 460TB method, and 19 were pyrazinamide resistant. The presence of active pyrazinamidase enzyme was sought by using the Wayne assay, which was positive in all of the sensitive isolates and four of the resistant isolates. The pncA gene was amplified by PCR, and mutations were sought by single-strand conformation polymorphism (SSCP) analysis. We identified four isolates which were phenotypically resistant to pyrazinamide, but which had active pyrazinamide enzyme on the Wayne assay and normal pncA gene SSCP. MICs measured by BACTEC 460TB and susceptibility testing at a lower pH of 5.5 confirmed genuine resistance. The pncA gene was sequenced in these four isolates and found not to have any mutations. This implies that an alternative mechanism of resistance exists in these strains. We conclude that genotypic assessment of pyrazinamide resistance is unreliable, because it depends on the identification of a single resistance mechanism. Phenotypic methods such as the BACTEC 460TB technique remain the best methods for pyrazinamide susceptibility testing.

Amidohydrolases↗
PubMed2000

False molecular clusters due to nonrandom association of IS6110 with Mycobacterium tuberculosis.

We sought to determine whether nonrandom association of IS6110 with Mycobacterium tuberculosis could result in false-positive clustering in unselected collections of isolates. We typed 196 strains of M. tuberculosis from an unselected community-based study in northern Tanzania by IS6110 and polymorphic GC-rich repetitive-sequence (PGRS) methodologies. The strains were analyzed by Gelcompar computer software. Analysis of 13 out of 25 groups showed that isolates with identical IS6110 and PGRS patterns were likely to be the same strain. Some IS6110 groups containing strains with identical PGRS patterns had similar IS6110 patterns that differed only by movement of the element. Isolates assigned to a single group (i.e., group 11) on the basis of sharing an identical IS6110 fingerprint pattern did not share identical PGRS fingerprint patterns. Six out of the nine bands in these isolates were in hot-spot locations, as previously defined. This indicates that nonrandom association may result in false-positive clustering in unselected community-based studies. Only strains with identical PGRS and IS6110 patterns are likely to be recently transmitted.

Bacterial Typing Techniques↗
PubMed1999

Length of time to laboratory diagnosis of Mycobacterium tuberculosis infection: comparison of in-house methods with reference laboratory results.

OBJECTIVES: To audit the time taken to obtain laboratory confirmation of infection with Mycobacterium tuberculosis using in-house methods of polymerase chain reaction (PCR) and culture and referral to a reference laboratory. METHODS: Retrospective collection of data from laboratory records covering a period of 1 year. RESULTS: Median time to microbiological diagnosis of a new infection using the in-house services in addition to the reference laboratory was 22.0 days. Using reference laboratory results alone, median time to diagnosis would have been 61.5 days. CONCLUSIONS: Development of on-site laboratory facilities to identify Mycobacterium tuberculosis can reduce the time to its identification by almost two-thirds.

Clinical Laboratory Techniques↗
PubMed1999

Activity of moxifloxacin against mycobacteria.

Moxifloxacin is an 8-methoxyquinolone compound with activity against a wide range of bacteria. We tested its activity in comparison with four other quinolones and isoniazid against clinical isolates of mycobacteria. It proved to be the most active of the quinolones tested against Mycobacterium tuberculosis (MIC90 0.25 mg/L), Mycobacterium avium-intracellulare (MIC90 1.0 mg/L), Mycobacterium kansasii (MIC90 0.06 mg/L) and Mycobacterium fortuitum (MIC90 1 mg/L). These data indicate that moxifloxacin merits further study as an antimycobacterial agent.

4-Quinolones↗
PubMed1999

Physiological cost of rifampin resistance induced in vitro in Mycobacterium tuberculosis.

Drug-resistant Mycobacterium tuberculosis is a major threat to public health. In clinical practice, a limited number of resistance mutations in a short sequence of the beta subunit of RNA polymerase (encoded by rpoB) have been described. Spontaneous resistance to rifampin was induced in vitro in M. tuberculosis H37Rv (ATCC 9360). Only three resistance patterns could be detected by PCR-single-strand conformation polymorphism analysis. Sequence analysis revealed that Ser(531)-->Leu arose most frequently, followed by His(526)-->Arg and then either His(526)-->Tyr or His(526)-->Asp. The relative Darwinian fitness of all but one of the mutant genotypes was less than that of the susceptible parent and, for these mutations, there was a significant correlation between fitness and clinical isolation rate (regression analysis P = 0.026). The fitness deficit in some mutants was small, suggesting that there is little likelihood of a spontaneous reversion to susceptibility.

Antibiotics, Antitubercular↗
PubMed1999

Detection of penicillin susceptibility in Streptococcus pneumoniae by pbp2b PCR-restriction fragment length polymorphism analysis.

A PCR-restriction fragment length polymorphism strategy directed against the pbp2b gene was evaluated for identification of penicillin susceptibility. A total of 106 United Kingdom (U.K.), 30 Danish, and 11 Papua New Guinean strains were tested. Of the U.K. strains, all the susceptible and all but one of the resistant isolates were correctly assigned. By using conventional definitions of "not resistant" and "not susceptible," the sensitivities were 97. 5 and 94.4%, the specificities were 100 and 98.9%, the positive predictive values were 100 and 94.4%, and the negative predictive values were 93.1 and 98.9%, respectively. This technique may allow susceptible (MIC, <0.1 mg/liter) and resistant (MIC, >1 mg/liter) isolates to be distinguished in a single PCR.

Aminoacyltransferases↗
PubMed1999

The role of the molecular laboratory in the investigation of Streptococcus pneumoniae infections.

The importance of infections with Streptococcus pneumoniae is being increasingly recognized. This has been emphasised by the emergence and international dissemination of penicillin-resistant strains. These factors challenge modern microbiologists to use molecular tools to speed the process of the diagnosis of S pneumoniae at each of the stages: rapid diagnosis, culture identification, and typing. The polymerase chain reaction (PCR) has been used to amplify a number of different targets for primary diagnosis of pneumonia, meningitis, otitis media, and bacteraemia. This may provide a rapid diagnosis in patients who have been partially treated with antibiotics and increase the diagnostic yield in clinical trials of antimicrobial agents and new vaccines. A new development is the use of PCR to rapidly determine penicillin susceptibility. Several different experimental protocols are reviewed. In the past serotyping using the capsule swelling, or Quellung reaction was the only typing method available. Recent insight into epidemiology and population genetics of S pneumoniae has shown that this technique is inadequate to study the transmission of this organism. New molecular typing techniques have been developed including Field version gel electrophoresis, ribotyping, restriction fragment end labeling, BOX PCR, and random amplification of polymorphic DNA. As these methods become available to clinicians, they will gain more understanding of the way in which this organism interacts with human populations.

Bacterial Typing Techniques↗
PubMed1998

RP59500 (Quinupristin/dalfopristin): three case reports of its use in infection due to Enterococcus faecium.

We describe three cases of Enterococcus faecium sepsis arising in immunocompromised patients, severely ill with other conditions, who were treated with the new injectable streptogramin RP59500. There are still few reports of clinical experience with this drug. All had bacteriological resolution, with one patient recovering fully. Although two of the three patients died, this was due to underlying disease in one case and a gram-negative superinfection in another. Quinupristin/dalfopristin therapy was not associated with significant adverse effects in any of the patients.

Adolescent↗
PubMed1998

New polymerase chain reaction-based diagnostic techniques for bacterial respiratory infection.

Polymerase chain reaction protocols are now available for the diagnosis of all of the major bacterial respiratory tract pathogens. Molecular techniques are also being used to determine the susceptibility of Streptococcus pneumoniae and Mycobacterium tuberculosis. In addition, polymerase chain reaction-based diagnosis will find a place in the investigation of the epidemiology of some pathogens such as Bordetella pertussis and Chlamydia pneumoniae. The added sensitivity will allow the detection of mild or asymptomatic cases or carriers who may play a role in sustaining the pathogen in the community.

Journal Article↗
PubMed1998

Nonrandom association of IS6110 and Mycobacterium tuberculosis: implications for molecular epidemiological studies.

IS6110 restriction fragment length polymorphism typing is now established as the primary typing method for Mycobacterium tuberculosis. It has been assumed that the position of bands is random. Thus, the discrimination of the technique increases in proportion to the copy number. Two collections of M. tuberculosis were investigated to test this hypothesis. We identified 33 positions in isolates from a Tanzanian collection and 25 positions in isolates from a London, United Kingdom, collection where bands were significantly more likely to be present than would be expected by chance. These data suggest that band position is not random, and this possibility may have an impact on the interpretation of molecular epidemiological studies of M. tuberculosis.

DNA Transposable Elements↗
PubMed1998

Fluoroquinolones: a new treatment for tuberculosis?

The fluoroquinolones have secured an important place in the management of bacterial infection, they are well absorbed orally, are found in respiratory secretions in higher concentrations than in serum and are concentrated inside macrophages. The agents are well tolerated and have an excellent safety record in long-term therapy. No new antituberculosis agents have been developed since the introduction of rifampicin into clinical use, so fluoroquinolones have been investigated for potential efficacy in tuberculosis. In vitro studies have shown that they are active against Mycobacterium tuberculosis at achievable concentrations. Treatment studies in mice have demonstrated efficacy. Few clinical studies have been performed in humans, but ciprofloxacin has demonstrated significant early bactericidal activity. Regimens including a fluoroquinolone have been comparable to other standard regimens, although the outcome in human immunodeficiency virus (HIV) seropositive patients was significantly poorer. There is still insufficient clinical data to use fluoroquinolones in first-line treatment of tuberculosis, but they may find a role in the management of multidrug-resistant infections or in patients with adverse reactions to other agents.

AIDS-Related Opportunistic Infections↗
PubMed1997

Allelic variation in Streptococcus pneumoniae autolysin (N-acetyl muramoyl-L-alanine amidase).

The lytA gene encoding the autolysin of Streptococcus pneumoniae may be a virulence determinant. Single-strand conformational polymorphism analysis demonstrated heterogenicity throughout the gene in clinical isolates and strains from the clonal serotypes 7 and 14. Sequence analysis of part of the choline-binding domain showed that in two isolates four amino acid substitutions occurred.

Alleles↗