Annales de microbiologie最新文献

An aminopeptidase was purified from the culture filtrates of a collagenolytic bacterium Empedobacter collagenolyticum. Purification of this enzyme was accomplished by ammonium sulphate precipitation, gel filtration on Sephadex-G200 and chromatography on DEAE-Sephacel. The purified enzyme seemed homogeneous on polyacrylamide gel electrophoresis. The molecular weight of the enzyme was about 100,000 daltons as determined by gel filtration on Sephadex-G200 but it was only 33,000 daltons by disc gel electrophoresis in the presence of sodium dodecyl sulphate. This enzyme selectively hydrolysed N-terminal arginine and lysine residues of peptides and arylamides substrates. The enzyme was strongly inhibited by EDTA, ZnCl2 and L-arginine.

Trichoderma harzianum was selected from 30 strains of cellulolytic fungi with the aim of producing cellulases by solid state fermentation of lignocellulosic substrates. Special attention was paid to cellulase production (i.e. carboxymethylcellulase and filter paper activity), apical growth and conidia production. Under the conditions of our experiments, T. harzianum exhibited the highest cellulasic activities with 1,315 IU/l of carboxymethyl cellulose and 80 IU/l of filter paper activity. Apical growth (1 mm/h) and yield of conidial production (3.25 x 10(10) conidia/g of substrate dry weight) were also valuable characteristics of this strain in the use of solid state fermentation.

The enzymatic activities of two reference strains of Haemophilus ducreyi and thirty clinical isolates were investigated by conventional biochemical tests and the API-ZYM test kit system which included 97 synthetic substrates. No strains converted delta-aminolevulinic acid to porphyrins, but they all reduced nitrates to nitrites. All strains possessed aminopeptidase activity against beta-naphthylamide derivatives of L-alanine, L-arginine, L-glutamine, glycine, L-leucine, L-lysine and L-serine. No trypsinor chymotrypsin-like activities were detected. All strains had phosphatase activity with broad pH range, and phosphoamidase activity. No glycosidase was detected by the substrates tested.

Cell-free extracts of Mycobacterium lepraemurium from mouse liver and M. leprae from armadillo liver were analysed for the presence of any mycobacterial catalase by using the specific inhibitor 3-amino-1,2,4-triazole and seroprecipitation titrations. These studies clearly demonstrated the presence of a "T" type of mycobacterial catalase in M. lepraemurium and placed it, in terms of immunological distance, in a position between M. tuberculosis and M. avium. The results did not reveal any detectable "T" catalase activity in the M. leprae preparations. The "M" type catalase activity which was observed did not bind to antisera against "M" catalase of M. kansasii, but was bound to the extent of 80% to antisera against normal armadillo liver catalase. The significance of the component of the "M" catalase in M. leprae preparations which did not react against antibodies to normal liver remains to be determined.

Saccharomyces boulardii became established in the digestive tract of monoxenic mice; the number of viable cells ranged around 10(7.5) per gram faeces. This yeast was drastically eliminated from the digestive tract of gnotoxenic mice harbouring a complex flora of human origin. In monoxenic mice harbouring S. boulardii, Candida albicans became established at a level equivalent to that observed in monoxenic mice harbouring C. albicans alone. If gnotoxenic mice received a concentrated suspension of viable S. boulardii cells so as to steadily maintain a population level close to 10(9) viable cells, C. albicans then became established at a level 10 to 50 times lower than that reached by the yeast strain alone. The antagonistic effect exerted in vivo by S. boulardii was preventive and curative. It was active against C. albicans, C. krusei and C. pseudotropicalis strains, but ineffective against C. tropicalis. This antagonistic effect disappeared when S. boulardii cells were killed by heating.

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.

The minimal inhibitory concentration (MIC) of chloramphenicol for a clinical isolate of Haemophilus ducreyi, strain CEB-10, was 16 micrograms/ml. This strain was also resistant to tetracycline (MIC = 64 micrograms/ml) and ampicillin. The presence of a chloramphenicol acetyltransferase (CAT) activity was demonstrated.

A method for the speciation of viridans streptococci (devoided of group antigens) is described. The major identification criteria are based on the reaction of a series of biochemical tests such as acid production in lactose, inuline, raffinose, mannitol and sorbitol, hydrolysis of arginine, esculin and Na hippurate, and production of polysaccharides in 5% sucrose media. A total of 460 strains were isolated from human specimens and identified as follows: 118 Streptococcus mitis, 102 S. sanguis II, 75 S. Sanguis I, 87 S. milleri (Streptococcus MG-intermedius), 28 S. mutans, 25 S. salivarius, 14 S. morbillorium, 2 S. uberis and 9 unspeciated. Susceptibility to antibiotics was studied for 318 strains: 63% of them were susceptible to all drugs tested; 37% of the strains were resistant to one or several antibiotics as follows: 34% to tetracycline, 8.5% to macrolides and related drugs, 5.3% to streptomycin and/or kanamycin (MIC greater than 2,000 micrograms/ml), 5% to penicillin (MIC = 1-4 micrograms/ml) and 4% to chloramphenicol.