Biomedical subjects
Publications and source records attributed to J G Magee.
The surgical and antimicrobial treatment of non-tuberculous mycobacterial lymphadenopathy in 17 children was reviewed. Node excision was curative, but most nodes were still incised leaving discharging lesions. Standard antituberculous treatment was unhelpful, but a new macrolide/quinolone combination appeared to be effective in three cases.
Sixty representatives of selected Mycobacterium and Nocardia species were examined for their ability to cleave 79 fluorogenic synthetic enzyme substrates based on the fluorophores 7-amino-4-methylcoumarin and 4-methylumbelliferone. The resultant data were analysed using the simple matching coefficient and clustering achieved using the unweighted pair group method with arithmetic averages algorithm. Clusters corresponding to the validly described species Mycobacterium bovis, M. chelonae, M. chitae, M. farcinogenes, M. fortuitum, M. peregrinum, M. senegalense, M. smegmatis, Nocardia asteroides, and N. farcinica were circumscribed at or above the 83% similarity level. Fluorogenic probes prepared from 7-amino-4-methylcoumarin and 4-methylumbelliferone provide a rapid means of detecting taxonomically useful enzymes in small amounts of whole mycobacteria and nocardiae.
An artificial neural network (ANN) was trained to distinguish between Mycobacterium tuberculosis and M. bovis with averaged pyrolysis mass spectra from duplicate subcultures of four strains of each of these species, each pyrolysed in triplicate. Once trained, the ANN was interrogated with spectrum data from the original organisms (the "training set") and from 26 other mycobacterial isolates (the "challenge set") of the M. tuberculosis complex (MTBC). Eight strains of M. bovis and 13 of M. tuberculosis, whether sensitive or variously resistant to antituberculosis drugs, were identified in agreement with conventional identification. Four strains of "M. africanum" were identified as M. bovis. Of two atypical M. tuberculosis strains from South India, one was identified as M. tuberculosis and the other as M. bovis. Six strains of BCG proved heterogeneous; two gave equivocal identifications, three were identified as M. bovis and one was identified as M. tuberculosis.
An artificial neural network was trained to distinguish between three putatively novel species of Streptomyces using normalised, scaled prolysis mass spectra from three representative strains of each of the taxa, each sampled in triplicate. Once trained, the artificial neural network was challenged with spectral data from the original organisms, the 'training set', from additional members of the putative novel taxa and from over a hundred strains representing six other actinomycete genera. All of the streptomycetes were correctly identified but many of the other actinomycetes were mis-identified. A modified network topology was developed to recognise the mass spectral patterns of the non-streptomycete strains. The resultant neural network correctly identified the streptomycetes, whereas all of the remaining actinomycetes were recognised as unknown organisms. The improved artificial neural network provides a rapid, reliable and cost-effective method of identifying members of the three target streptomycete taxa.
Isolates of Mycobacterium avium-intracellulare complex (MAI) from AIDS and non-AIDS patients were compared by pyrolysis mass spectrometry (PyMS). Those from AIDS patients were more closely related to each other than those from non-AIDS patients which were significantly more disparate.
Thirty four cultures of slow growing, Tween-80 negative mycobacteria were analysed by pyrolysis mass spectrometry. The results showed that pyrolysis mass spectrometry could positively distinguish strains of Mycobacterium xenopi from those of the Mycobacterium avium-intracellulare (MAI) complex. Pyrolysis mass spectrometry may be a useful technique for the rapid characterisation of non-tuberculous mycobacteria in such clinical settings as their isolation from immunocompromised patients-for example, those with AIDS.
32 isolates belonging to the Mycobacterium tuberculosis complex were examined by pyrolysis mass spectrometry (PyMS). This technique demonstrated that recent clinical isolates of M. africanum were indistinguishable from those of M. bovis and together formed a homogeneous group distinct from M. tuberculosis. Isolates of BCG were heterogeneous and more closely related to laboratory-adapted strains of M. tuberculosis than to recent isolates of either M. tuberculosis or M. bovis. PyMS is a simple and inexpensive technique which gives interesting information on the relationships between members of the M. tuberculosis complex and can make the clinically important distinction between strains of M. bovis and M. tuberculosis accurately and much more rapidly than conventional techniques.
A monoclonal antibody-based immunofluorescence test for the detection of Pneumocystis carinii was evaluated in comparison with the conventional direct staining by Grocott's silver methenamine technique. A total of 254 respiratory samples from HIV positive and other immunocompromised patients were examined. Cysts were detected in 30 (12%) of samples using the monoclonal test, but only 15 (6%) positives were found using the Grocott method. There is need for a speedy and efficient test for detection of these organisms, and the monoclonal test was found to be more reliable, quicker and more sensitive than the Grocott technique.
We report six patients colonised with a multiply resistant strain of Streptococcus pneumoniae.
We report a 6 year experience (1979-1984) of isolating Mycobacterium malmoense in the north-east of England. Eleven subjects were involved of whom 10 had active infection--9 pulmonary, one cervical adenitis. The 11 new isolates represent 0.7% of all new mycobacterial isolates during this period and 10% of new non-tuberculous isolates. In all but 2 cases there was pre-existing pulmonary disease and/or a recognised predisposing factor to mycobacterial infection. The organisms were generally insensitive to isoniazid but sensitive to both rifampicin and ethionamide. The results of chemotherapy are described.