Biomedical subjects

F Portaels

Publications and source records attributed to F Portaels.

165 records · Page 10Linked to original sources

PubMedDate not supplied

Correlation viability/morphology in Mycobacterium leprae.

The present study regards the correlation between the percent of viable M. leprae (as determined by the mouse foot pad technique) and the quantitative ultrastructural analysis of M. leprae cells in 6 armadillo's samples and 1 nude mouse foot pad. The quantitative ultrastructural study of 3 LL patients and 1 M. leprae-infected nude mouse was correlated to the Morphological Index. The results show that most M. leprae cells with continuous undeformed cell walls, continuous symmetric membranes, ribosomes and fibrilar nucleoids are viable bacilli. Some cells with the above ultrastructural pattern may be dead bacilli that did not yet enter the macrophage-induced degradative process that results in the disposal of the bacteria. Our results also show that degenerating M. leprae cells largely predominate in most samples studied. This means that, even in the absence of anti-leprosy treatment, dead M. leprae cells accumulate in the host's tissues. This point has to be taken into account in the calculation of the generation time of M. leprae in vivo, the dynamics of the leprosy bacillus in susceptible hosts being influenced by the simultaneous occurrence of growth, death and degradation. Since known facts in regards to the physiology of bacterial membranes make it difficult to accept the PAS-symmetric membrane of viable M. leprae as the membrane of growing bacilli, a search of M. leprae cells with asymmetric membranes was undertaken in appropriate samples from nude mice. Several M. leprae cells with normal ultrastructure and Thiéry-asymmetric membranes were found in the foot pads of one mouse. Although this observation must be confirmed in another sample, it suggests that M. leprae would not be an exception to the general concept that the membranes of all growing Gram-positive bacteria have PAS-positive components located only in the outer layer. The M. leprae cells that have normal ultrastructure and symmetric membranes and that are viable would represent some sort of resting cells, that is, living but not growing bacteria. All the, 11, 263 individual bacillary profiles scored in the ultrastructural study included in the present study exhibited the micromorphological characteristics of acid-fast bacteria.

Animals↗

PubMedDate not supplied

Growth of mycobacteria in relation to the pH of the medium.

The influence of pH on the growth of mycobacteria on Loewenstein and Dubos OAA media was studied with 56 strains belonging to 10 species of rapidly growing and 16 species of slowly growing mycobacteria. pH gradients were obtained by the use of McIlvaine's citrate and Sörensen's citrate buffer. The sensitivity of mycobacteria at different pH values of the medium was independent of the culture medium and buffer used. Minimal, maximal and optimal pH values were specific for each species, all strains of the same species producing identical results. Some slowly growing mycobacteria such as Mycobacterium lepraemurium developed within a very narrow optimal pH range: between 5.8 and 6.1. Other species developed over a wide optimal pH range, e.g. M. nonchromogenicum: from 5 to greater than 7.4. For slow growers, in general, with the exception of M. lepraemurium, optimal pH was between 5.8 and 6.5. In general, rapidly growing mycobacteria developed over a wider pH range of more than 2 units. All strains, with the exception of M. chelonei, developed optimally between pH 7 and 7.4. For M. chelonei, as for slower growing species, the optimal pH was between 5.4 and 6.5. Taxonomically related species such as M. tuberculosis and M. bovis, M. kansasii and M. gastri, M. microti and M. bovis BCG, and M. vaccae and M. parafortuitum, were inhibited or stimulated at identical pH values. This specificity constitutes a supplementary taxonomic character. At certain pH values, some species otherwise difficult to separate may be differentiated: e.g. M. avium, not growing at pH 4.6, is distinguished from M. scrofulaceum which does grow at pH 4.6. For routine diagnostic purposes, Loewenstein Jensen medium at pH 7 is not optimal; Ogawa medium, with its pH of 6, is more appropriate.

Culture Media↗

PubMedDate not supplied

Mycobacterium paratuberculosis and Mycobacterium avium subsp. silvaticum DNA cannot be detected by PCR in Crohn's disease tissue.

BACKGROUND: The etiology of Crohn's disease remains unknown. A putative mycobacterial cause of the disease is still controversial. AIMS: To assess the mycobacterial hypothesis in Crohn's disease using a polymerase chain reaction technique. PATIENTS AND METHODS: Nested polymerase chain reaction with primers on the 16S-rRNA coding region (16S-rDNA) and with primers specific both to the insertion sequences (IS) 900, and IS 901/902 were used to amplify Mycobacterium paratuberculosis or Mycobacterium avium subsp. silvaticum DNA in frozen endoscopic intestinal biopsies or surgical resection specimens from patients with Crohn's disease (n = 47: 25 endoscopic biopsies and 22 surgical resection samples, +/- lymph nodes), ulcerative colitis (n = 27), and non inflammatory bowel diseases (n = 20: colonic tumors and diverticulitis). Positive as well as negative controls were used throughout the study. RESULTS: All strains of Mycobacterium paratuberculosis and Mycobacterium avium subsp. silvaticum tested were positive for both primer systems. Of the 94 biopsies tested, 5 (2 Crohn's disease, 1 ulcerative colitis and 2 controls) were positive with the 16S-rDNA primers but did not correspond to Mycobacterium paratuberculosis or Mycobacterium avium subsp. silvaticum. None of the specimens was positive with the IS primers. CONCLUSION: These results do not support the hypothesis that Mycobacterium paratuberculosis, or Mycobacterium avium subsp. silvaticum play a role in Crohn's disease.

Adult↗