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J T Magee

Publications and source records attributed to J T Magee.

At least 19 recordsLinked to original sources
PubMed1997

Pyrolysis mass spectrometry: data processing in classification studies.

A scheme for numerical processing of pyrolysis mass spectrometry (Py-MS) data is detailed, along with methods for combining the results of conventional phenotypic and Py-MS taxonomic surveys. The importance of this combined approach in polyphasic taxonomy is emphasised; it yields data on cell composition and the nutritional and physiological interactions of strains with their environment. Large collections of strains can be surveyed rapidly and economically, yielding presumptive classifications, which may then be confirmed with a few representative strains in more demanding, difficult and expensive approaches. An objective, non-arbitrary method of establishing suitable cut-off points to delineate group structures in dendrograms is also described.

Bacteria↗
PubMed1997

A numerical taxonomic study of Streptococcus sanguis, S. mitis and similar organisms using conventional tests and pyrolysis mass spectrometry.

Numerical taxonomic methods were applied to the results of pyrolysis mass spectrometry (Py-MS) and conventional test reaction patterns (CTRPs) obtained with 46 strains of oral streptococci identified as representative of six species. Of these: Streptococcus gordonii strains formed a single homogeneous well-differentiated cluster both in the Py-MS and CTRP analyses; S. oralis strains were more diverse, forming 2 CTRP and 3 Py-MS clusters; S. crista, S. parasanguis and S. sanguis formed clear, but diverse and poorly differentiated clusters on the basis of CTRPs, and were poorly differentiated in the Py-MS analysis; and S. mitis strains were clearly diverse in both analyses. Peritrichously fimbriate ('tufted') S. mitis strains formed a tight cluster, well differentiated from the type strain in both Py-MS and CTRP analyses, and may represent a previously unrecognised centre of variation.

Humans↗
PubMed1997

Epidemiological typing of Klebsiella pneumoniae by pyrolysis mass spectrometry.

Thirteen isolates of ceftazidime-resistant Klebsiella pneumoniae from a suspected cross-infection outbreak involving patients on an intensive care unit and a haematology ward were examined in pyrolysis-mass spectrometry (Py-MS), along with eight concurrent non-outbreak-associated clinical isolates of klebsiellae as controls. Py-MS showed tight clustering of the suspected outbreak isolates, suggesting cross-infection with a single strain. Non-outbreak isolates were clearly distinct from one another and from the outbreak strain. The results confirm that Py-MS is a powerful tool for rapid strain comparison in investigations of cross-infection incidents.

Bacterial Typing Techniques↗
PubMed1997

Pyrolysis mass spectrometry: a predictor of clinical response to treatment in pulmonary opportunist mycobacterial infection: preliminary work with M. malmoense.

Pyrolysis mass spectrometry (Py-MS) yields data reflecting overall cell composition. The changes in composition induced by treatment with rifampicin and ethambutol, alone and in combination, were investigated for a collection of seven strains of Mycobacterium malmoense from pulmonary infections. Two strains, both from patients that had responded to therapy with this combination, showed large changes in composition from control, untreated cultures. The difference was particularly marked for the ethambutol treated cultures. Four strains, all from patients who had failed to respond to therapy with this combination, showed minimal changes in composition for all treatments. The remaining strain also showed minimal treatment-induced change, but, for this patient, therapy with the combination had proved successful. Minimum inhibitory concentrations (MICs) were determined radiometrically. All strains showed MICs < 0.5 microgram/mL for rifampicin (sensitive) and of 8 micrograms/mL for ethambutol (resistant). MIC results did not correlate with clinical response, whereas the Py-MS results correlated with clinical response for six of the seven isolates. Py-MS may have a role in predicting effective therapy for this problem group.

Ethambutol↗
PubMed1997

A pyrolysis mass spectrometry study of temperature-dependent compositional shifts in Xanthomonas (Pseudomonas) maltophilia.

Xanthomonas (Pseudomonas) maltophilia strains are frequently susceptible to aminoglycoside antibiotic and polymixin B when incubated at 37 degrees C, but resistant at 30 degrees C. Five strains showing temperature dependent resistance, and five that did not were examined by pyrolysis-mass spectrometry, a characterisation method that gives fingerprint data reflecting cell composition. Cultures grown at 30 degrees C and 37 degrees C in the absence of antibiotic were analysed. Strains showing temperature-dependent resistance exhibited a characteristic compositional difference between cells grown at the two temperatures, whereas strains not showing this type of resistance varied widely in the extent and nature of temperature-dependent differences in composition. The precise nature of the chemical differences cannot be elucidated at present, but could be determined by examining purified cell constituents.

Mass Spectrometry↗
PubMed1997

Applications of pyrolysis mass spectrometry in studies on the mode of action of antimicrobial agents.

Changes in overall cell composition during exposure to antimicrobial agents were investigated by pyrolysis mass spectrometry (Py-MS) in parental (O+K+), K antigen deficient (O+K-), and O and K antigen deficient (O-K-) strains of Klebsiella aerogenes NCTC 5055. Changes followed distinct patterns that correlated with mode of action: penicillin binding protein (PBP) 3 blockade (ceftazidime, piperacillin); PBP 2 blockade (imipenem); membrane disruption (colistin); bacteriostatic (chloramphenicol), and bactericidal (gentamicin) protein synthesis inhibition; and DNA synthesis inhibition (ciprofloxacin). Changes were pronounced after exposure for 1 hour at 10 x MIC. In general, the O-K- strain showed the largest compositional shifts, and the parental O+K+ strain the least shifts, correlating with bactericidal kinetic studies. Py-MS may be useful in studies of the mode of action of antimicrobial agents, particularly in early screening of new compounds, and in rapid detection of the effects of antimicrobial agents on micro-organisms.

Anti-Bacterial Agents↗
PubMed1997

Effect of temperature on aminoglycoside binding sites in Stenotrophomonas maltophilia.

In this study we used strains of Stenotrophomonas maltophilia grown at 30 degrees C and 37 degrees C to investigate the role of lipopolysaccharide (LPS) in temperature-dependent variations in sensitivity (TDVS) to gentamicin. TDVS was scored as 'good' if a four-fold or greater difference in minimum inhibitory concentration (MIC) was found between the two incubation temperatures (good TDVS strains; n = 23), and otherwise as 'poor' (poor TDVS strains; n = 15). Phosphate content of isolated LPS in the strains exhibiting good TDVS grown at 37 degrees C was significantly (P < 0.001) higher than those grown at 30 degrees C. However, the phosphate content from LPS of strains exhibiting poor TDVS did not alter significantly with growth temperature. There was no significant difference in 3-deoxy-D-manno-octulosonic acid (KDO) content between the strains grown at the different incubation temperatures. Fluorescence-activated cell sorting analysis showed significant differences in binding of fluorescein Isothiocyanate conjugated gentamicin to cells grown at 30 degrees C or 37 degrees C. We conclude that the temperature-dependent variation in the aminoglycoside susceptibility of this species was not correlated with any detectable change in KDO content, but correlated well with phosphate content of LPS and that LPS phosphate is the major site of ionic interaction for aminoglycosides in S. maltophilia.

Anti-Bacterial Agents↗
PubMed1997

Characterization of smooth and rough morphotypes of Peptostreptococcus micros.

Isolation of the smooth (Sm) morphotype of Peptostreptococcus micros, a suspected oral pathogen, is sometimes accompanied by isolation of a rough (Rg) morphotype of P. micros. The Rg type readily changes to a Sm-like variant (RgSm) in broth culture. Sm and Rg isolates and RgSm variants were compared to determine whether these three types are the result of phase variation. The RgSm variants resembled the Sm morphotype in colony morphology; furthermore, the Sm type and the RgSm type did not have the fibrillar surface structures characteristic of the Rg type, and the Sm and RgSm types were more hydrophobic than the Rg type. However, when we compared the sodium dodecyl sulfate-polyacrylamide gel electrophoresis patterns of whole-cell proteins, serotyping data, pyrolysis mass spectrometry data, 16S ribosomal DNA sequences, and hemolytic activities, the RgSm variants and the Rg isolates were very similar and were clearly distinct from the Sm isolates. These results suggest that the Rg and RgSm types form a cluster distinct from the Sm type and thus provide evidence that P. micros can be differentiated into two groups, one consisting of the Sm type and the other consisting of the Rg and RgSm types.

Base Sequence↗
PubMed1997

A comparative study of Fusobacterium necrophorum strains from human and animal sources by phenotypic reactions, pyrolysis mass spectrometry and SDS-PAGE.

Fusobacterium necrophorum strains from human infection (21) were compared with strains from animals (17 biotype A, 2 biotype AB, 4 biotype B, 1 biotype unknown), and the type strain NCTC 10575 in conventional tests reaction patterns (CTRPs), SDS-PAGE and pyrolysis mass spectrometry (PMS). Classifications from the three approaches showed one major consensus group comprising all human strains, and another comprising animal biotype A strains. Animal biotype B strains and one animal strain, designated with some doubt to biotype A, were outliers of the consensus 'human strain' group. Again, animal biotype AB strains were outliers of the consensus 'animal biotype A group', as was the type strain, which was clearly atypical in conventional tests and PMS. Colonial and microscopic characters showed good discrimination between the major consensus groups. However, only haemagglutination and the API-ZYM leucine arylamidase of the biochemical tests discriminated well between these groups. The 'animal biotype A group' clearly corresponds to F. necrophorum subsp. necrophorum, but synonymy of F. necrophorum subsp. funduliforme with the group of human strains was less certain. The latter subspecies was described solely on the basis of animal strains, all of biotype B, but each of four animal biotype B strains in this study was an outlier of the 'human strain group' in one or more of the characterisation approaches. Strains of F. necrophorum causing human infection were clearly distinct from the biotype A strains commonly found in animal infection. This has implications for the validity of animal models of human necrobacillosis. In view of these differences, it would be useful to have a validated designation for strains causing human infection. However, it would be premature to assume that the definition of F. necrophorum subsp. funduliforme encompasses the human strains in the absence of confirmatory DNA-homology and 16S rRNA-sequencing studies.

Animals↗
PubMed1996

Resistotyping of campylobacters: fulfilling a need.

A 9-month trial of a simple typing scheme for ¿thermophilic' enteric campylobacter isolates at a large Public Health Laboratory is described. Resistotyping was performed with six agents in a method modified by Bolton and colleagues from an earlier scheme, and biotyping was performed by a modified Lior scheme involving three tests. Reproducibility was excellent in both schemes, with test variation < 2%. Five household clusters and one larger presumptive milk-borne outbreak were identified in this scheme, and confirmed in pyrolysis mass spectrometry. The 328 isolates from new patients, excluding duplication from these clusters, were divided into 35 resistotypes with the largest group comprising 22% of isolates. In combined bio- and resistotyping, 86 types were found, with the largest group comprising 9.5% of isolates. The results are contrasted with salmonella sero- and phage-typing, where, on the same basis, the 176 isolates in the same period were divided into 40 groups, with the largest comprising 45% of isolates. Resistotyping, with or without additional biotyping, proved to be a convenient, simple, rapid, highly discriminatory, reproducible and inexpensive method well suited to use in local laboratories. It is a strong candidate for first-line national and local surveillance of campylobacter infections, fulfilling a need for monitoring of this important cause of enteric disease.

Adult↗
PubMed1996

Temperature-dependent aminoglycoside resistance in Stenotrophomonas (Xanthomonas) maltophilia; alterations in protein and lipopolysaccharide with growth temperature.

Clinical strains of Stenotrophomonas (Xanthomonas) maltophilia often show large, growth temperature-dependent, variations in their susceptibility (TDVS) to aminoglycoside antibiotics. Strains showing more than a fourfold increase in susceptibility between 30 degrees and 37 degrees C (TDVS+ strains; n = 23) were contrasted with those showing lesser variation (TDVS- strains; n = 15) in studies of growth temperature-dependent variation in protein and cell-wall lipopolysaccharide (LPS) electrophoresis patterns in an attempt to determine the mechanism of TDVS. Several proteins showed increased intensity with increasing growth temperature. These comprised bands at c. 65, 55, 42.5, 26 and 21.5 kDa in the whole cell proteins, an outer membrane protein band at c. 21.5 kDa, and cytoplasmic membrane protein bands at c. 42.5 and 27 kDa. Two whole cell protein bands at c. 30 and 24 kDa and three outer membrane protein bands at c. 45, 30 and 24 kDa decreased in intensity with increasing growth temperature. However, there was no correlation with the extent of variation in susceptibility, either in the extent of temperature dependent changes in protein banding patterns, or the presence or absence of specific protein bands. By contrast, temperature-dependent variation in LPS patterns correlated well with TDVS. TDVS+ strains yielded intense ladder patterns of more than 30 discrete bands, and the mean molecular weight of the ladder pattern was markedly higher at growth temperatures < or = 30 degrees C, than at > or = 37 degrees C. TDVS- strains gave a clearly distinct high mol. wt LPS banding pattern showing fewer, less intense bands and a smaller and less consistent shift in mean molecular weight with temperature. Strains which were clearly resistant at 30 degrees and 37 degrees C, had a high mol. wt. polysaccharide component but an absence of the typical LPS-ladder pattern. We conclude that the temperature-dependent variation in the aminoglycoside susceptibility of this species was not correlated with any detectable change in protein composition, but correlated well with changes in LPS structure.

Aminoglycosides↗
PubMed1995

Analysis of Bacteroides species by pyrolysis mass spectrometry.

Two methods for the classification of isolates of the Bacteroides fragilis group were compared in a study of 133 clinical isolates and 10 reference strains. There was broad similarity between the pattern of clusters in pyrolysis mass spectrometry (PyMS), which reflects whole-cell composition, and that in conventional tests, which reflect nutritional interactions with the environment. A single large cluster was resolved by both approaches; this cluster comprised mainly strains identified as B. fragilis and was surrounded by a multiplicity of small clusters (42 in PyMS and 24 in conventional tests). Individual clusters corresponding to strains identified as Bacteroides thetaiotaomicron and Bacteroides vulgatus, respectively, were found by both techniques. However, for the remainder of strains, little correlation was evident between clustering in PyMS and that in conventional tests. Further comparison with data obtained by sodium dodecyl sulfate- polyacrylamide gel electrophoresis for this collection of strains showed equal levels of disagreement between classification based on whole-cell protein and each of the classifications described here. In previous studies of other genera, PyMS-based and conventional test-based classifications showed good agreement. It appears that the B. fragilis group presents intractable problems in phenotypic characterization.

Bacterial Typing Techniques↗
PubMed1995

Growth temperature-dependent variation of cell envelope lipids and antibiotic susceptibility in Stenotrophomonas (Xanthomonas) maltophilia.

Clinical isolates of Stenotrophomonas (Xanthomonas) maltophilia showed growth temperature-dependent variation in susceptibility (TDVS) to aminoglycoside antibiotics between 30 degrees C and 37 degrees C, but little or no TDVS effect for polymixin B, colistin, ceftazidime, chloramphenicol and piperacillin. When phenylethanol was added at sub-inhibitory concentrations, the TDVS effect was eliminated. Gas liquid chromatography showed that 13-methyl tetradecanoate (i-15;0), was the predominant fatty acid, and was present in lower proportions in cells grown at 30 degrees C than 37 degrees C, by contrast to the unsaturated acids, which were found in increased proportions in cells grown at 30 degrees C. However, the extent of these shifts in composition did not correlate with the extent of the TDVS effect in individual strains. Membrane analysis by spin label-electron spin resonance spectroscopy showed that strains exhibiting TDVS had significantly decreased membrane fluidity compared with susceptible strains at 30 degrees C. Furthermore, analysis of the outer and cytoplasmic membranes from the strains with TDVS revealed that in organisms grown at 30 degrees C, the outer membrane remained in a more rigid conformation than the cytoplasmic membrane. We conclude that resistance of S. maltophilia to aminoglycoside antibiotics at 30 degrees C correlates with changes in the conformation of the outer membrane so that binding and/or uptake of the antibiotic is inhibited.

Anti-Bacterial Agents↗
PubMed1995

A numerical taxonomic study of the gram-positive anaerobic cocci.

Clinical (101) and collection (26) strains of gram-positive anaerobic cocci were examined in conventional tests and pyrolysis mass spectrometry (PMS). Numerical classifications based upon conventional test reaction patterns (CTRPs) and PMS showed 27 and 22 clusters, respectively. Cross-tabulation of cluster membership in the two classifications showed excellent correlation, with the combined classifications showing clear groups corresponding to the currently recognised species Peptostreptococcus anaerobius, P. heliotrinreducens, P. hydrogenalis, P. indolicus, P. lactolyticus, P. magnus, P. micros and Peptococcus niger. Strains of P. prevotii and P. tetradius clustered together in a heterogeneous group of saccharolytic organisms. However, strains previously identified as P. asaccharolyticus were divided into three distinct groups in PMS, two of which differed only in indole-associated pyrolysis products. A further four groups and several single-member clusters were distinct from these species. PMS data supported the validity of identification by pre-formed enzyme profiles and confirmed that Hare group III is synonymous with P. hydrogenalis, Hare group IV with P. magnus, and the "ADH group" with P. vaginalis. There is clearly a need for a taxonomic revision of the genus Peptostreptococcus, which probably encompasses several generic groups.

Bacteria, Anaerobic↗
PubMed1994

Pyrolysis typing of isolates from a recurrence of systemic cryptococcosis.

Cryptococcal meningitis was diagnosed in a 71-year-old male diabetic patient with underlying ischaemic heart disease, asthma and bilateral axillo-femoral vascular grafts. After treatment with fluconazole for 2 months, the patient appeared to be cured. Two years later he presented with an aneurysm of the right graft that was resected and replaced with a new graft segment. Cryptococcus neoformans var. neoformans was grown from post-operative blood cultures and samples of the excised graft. The patient was treated with fluconazole and discharged after 6 weeks. Multiple isolates from both episodes had been preserved, and these, together with isolates from other UK patients, were cultured in duplicate, blind coded and characterised by pyrolysis mass spectrometry (PMS). Duplicate culture and re-isolate sets formed tight clusters, with each patient set clearly distinct. Sets of isolates from the two episodes in this patient formed a single tight cluster and were indistinguishable by PMS. These results support the contention that C. neoformans infection can be reactivated after being dormant for a prolonged period.

Aged↗
PubMed1993

An investigation of a nosocomial outbreak of Clostridium difficile by pyrolysis mass spectrometry.

Isolates from a presumptive nosocomial outbreak of Clostridium difficile infection at a large teaching hospital were typed by pyrolysis mass spectrometry (PMS) and antibiograms. One isolate, from the putative index case, was dissimilar from the outbreak strain, but 24 isolates from 16 patients were indistinguishable by both methods. The outbreak centred on two wards for the acute care of the elderly, with a few cases elsewhere. Transfer of patients appeared to be the route of transmission between wards. There was a significant fall in the incidence of cases following intervention by the Infection Control Unit. This included ward inspection, advice on antibiotic usage and advice on prevention of faecal-oral transfer, particularly by proper handwashing. Subsequent monitoring of C. difficile infection showed a background of sporadic, dissimilar isolates with occasional apparent cross-infection incidents limited to a few patients. In suspected outbreaks, patterns of antibiotic susceptibility may be useful in initial screening, before referral for more sophisticated typing. There was excellent correlation between PMS results, antibiograms and epidemiological information.

Aged↗