Annales de microbiologie最新文献

In this supplement are given the characters of 41 new Salmonella serovars recognized in 1982 by WHO collaborating Centre for reference and research on Salmonella: 16 belong to the sub-genus I, 18 to the sub-genus II, 6 to the sub-genus III and 1 to the sub-genus IV.

Twenty strains of free-living N2-fixing bacteria, isolated from the endorhizosphere of rice in rice soils of Senegal, were studied on the basis of 259 morphological, physiological, biochemical and nutritional characters. Half of them were Gram-negative small rods with polar flagella and showing a strictly respiratory metabolism; they were characteristic of the genus Pseudomonas. A first group of 6 strains was related to the P. cepacia-P. marginata group characterized by lophotrichous flagella; they accumulated polyhydroxybutyrate, assimilated arginine and betaine, grew at 41 degrees C and showed a wide nutritional spectrum with DNA GC% of 67-68. The second group of 4 strains was related to the P. lemoignei group because of (a) its monotrichous flagella, (b) poly-beta-hydroxybutyrate accumulation, (c) failure to assimilate arginine and betaine and to grow at 41 degrees C, (d) lack of arginine dihydrolase and (e) its narrow nutritional spectrum. DNA GC% was 65. These 4 strains were also denitrifying bacteria. Six strains were related to the genus Alcaligenes because of their strictly respiratory metabolism and their peritrichous flagella; their nutritional spectrum was variable and one of them was a denitrifier. DNA GC% was 68. One strain was related to Aeromonas hydrophila of the Vibrionaceae family; it consisted of Gram-negative and oxidase-positive small rods with monotrichous polar flagella and respiratory and fermentative metabolism without gas evolution. This strain essentially assimilated sugars and its DNA GC% was 63. Another strain was a Gram- and oxidase-negative small rod with peritrichous flagella and respiratory and fermentative metabolism with gas evolution. Sugars, organic acids and amino acids were assimilated. The DNA GC% was 53. This strain was related to Enterobacter cloacae of the Enterobacteriaceae family, but it showed the additional faculty of denitrification. The last two strains studied were spirilla with amphitrichous flagella characteristic of the genus Aquaspirillum. They showed a strictly respiratory metabolism and a DNA CG% of 60-64. This study allowed us to show the N2-fixing capacity of species of Pseudomonas, Alcaligenes and Aeromonas which had been devoid of N2-fixing bacteria until this time. All strains studied were microaerophilic for N2 fixation.

A simple and quantitative method for the alkaline hydrolysis of fatty acid derivatives occurring in the lipids of mycobacteria is described. After methylation, the lipidic mixtures were chromatographed on a thin layer of silicagel. The contents in mycolates and secondary alcohols allowed the distinction of 9 groups among the 27 species studied. Such an analysis is generally insufficient to identify a species, but its discriminating power differs from that of other commonly-used methods. Complementary tests chosen according to each particular situation are necessary, including vapour phase chromatography applied to the same lipidic mixture as that used for thin-layer chromatography. Coupling of the two chromatographic methods would allow the recognition of 22 groups among the 27 species of mycobacteria studied.

Among Shigella flexneri serotypes, serotype 6 (28 strains) was individualized from serotypes 1 to 5 (43 strains) by electrophoresis and isoelectric focusing of esterases. The taxonomic status of S. flexneri serotype 6 should be reconsidered in light of this work.

Four strains of Bacillus circulans sensu stricto (ATCC 4513 (type strain), 4515, 4516, and 4530) were subjected to 236 morphological, biochemical and physiological tests, including 162 carbon source utilization tests. B. circulans s. s. is a species of facultative anaerobes able to ferment carbohydrates. Many carbohydrates and a few aliphatic acids were used as sole carbon and energy sources, but amino acids were not. The guanine-plus-cytosine content of DNA (four strains studied) was 37.2 +/- 0.4 mol% (mean +/- standard deviation).

Two strains of Salmonella typhi resistant to streptomycin, tetracycline, chloramphenicol and sulfonamides were studied. Conjugation and analysis of plasmid DNA suggested that in the two strains, these resistance characters were mediated by a single R plasmid. The plasmids of both strains belonged to the FI-incompatibility group, whereas that isolated from the resistant Mexican S. typhi belonged to incomtibility group H. Therefore, the two resistant S. typhi isolated in Belgium do not represent an extension of the H plasmid which was responsible for chloramphenicol resistance in S. typhi during the 1972 Mexican epidemic.

A comparative study of the sensitivity to metronidazole and ornidazole of 127 anaerobic or microaerophilic strains isolated from various clinical samples showed that the activity of both products was similar: the distribution of sensitive and resistant strains was identical. However, the in vitro activity level of metronidazole was slightly higher. This difference, though statistically significant, had no incidence on therapeutic indications. The determination of sensitivity towards the two nitroimidazoles was carried out by three methods: broth dilution and agar diffusion for metronidazole; and broth dilution and disk-broth for ornidazole. Two of these methods, broth dilution and disk-broth, gave concordant results. Conversely, the limits of the agar diffusion technique were shown to be related to independent biological factors such as bacterial motility and slow growth rate. The poor accuracy of this method limits its use in detecting total resistance.

Axenic mice died with signs of enterotoxaemia after oral ingestion of Clostridium perfringens type C or D. Under the same conditions, C. perfringens type B was less pathogenic, and types A and E showed no pathogenicity. The microflora of conventional mice prevented the establishment of C. perfringens types B, C and D in the digestive tract and protected them against the pathogenicity of these strains. Toxins produced in the caecum of monoxenic mice harbouring C. perfringens type C were not neutralized by the anti-C. perfringens type C antiserum. This suggests that the toxins produced in vivo by this strain were different from those produced in vitro.