Annales de microbiologie最新文献

An ELISA method on microtitration plates to detect and assay Escherichia coli heat-labile enterotoxin (LT) is described. This technique is rapid and simple to perform in any laboratory. It allows detection of the presence of LT with the naked eye within 10 h in a 12-h E. coli culture supernatant. The reaction is based on immunological cross-reaction between LT and the Vibrio cholerae toxin (CT). In place of traditional microtitration plates coated with ganglioside Gm1, we propose a new polystyrene support coated with purified anti-CT antibodies. This coated support has been conditioned in a kit to be used in laboratories in bush dispensaries of endemic areas. It was tested with 40 enterotoxigenic (LT+) strains isolated from stools of diarrhoeal children and with 14 LT- strains. All supernatants LT+ and LT- were found positive and negative, respectively, with the ELISA method and with the new polystyrene support. Field tests (in Wallis, Futuna et Vanuatu) with the new kit and standard method were satisfactory.

A modification of the technique described by Evans for the production of Escherichia coli heat-labile enterotoxin was employed. Instead of Casamino yeast extract medium, which is toxic for Vero cells, Eagle's minimal essential medium (MEM) commonly used in cell cultures was substituted and the LT toxin produced in MEM was assayed on Vero cells.

The susceptibility of 139 strains of Listeria towards eight antibiotics--penicillin, ampicillin, cephalotin, gentamicin, chloramphenicol, tetracycline, erythromycin and pefloxacin--was studied. All strains were susceptible to all antibiotics except pefloxacin. The lowest MIC (less than or equal to 0.5 mg/l) were obtained with penicillin, ampicillin, gentamicin and erythromycin. For tetracycline, cephalotin and chloramphenicol, MIC ranged from 0.5 to 16 mg/l. The MIC of pefloxacin varied from 4 to 16 mg/l.

Ten medically or environmentally significant strains of bacteria were assessed as to their metallic content (Be, Mg, Cr, Mn, Fe, Co, Cu, Zn, Cd and Pb). Metallic detection was performed using a carbon rod-equipped atomic absorption spectrophotometer. Experimental parameters such as heavy metal content of initial culture medium, incubation, "red fuming" nitric acid digestion times, evaporative losses (and their individual correction) plus primary sample dilutions, were standardized. For the ten strains studied, characteristic metallic profiles were observed. More work is needed to assess the taxonomic and epidemiologic significance of metallic profiles of microorganisms.

Coagulase-negative staphylococci, and in particular Staphylococcus epidermidis, are now being recognized as causing human infections with increasing frequency; the absence of an internationally accepted system of phage-typing for coagulase-negative staphylococci led us to isolate new phages. Fifty strains of S. epidermidis isolated from human infections were induced with mitomycin C: eight phages (41, 63, 118-II, 138, 245, 336, 392 and 550) were isolated. These phages were propagated on five different strains of S. epidermidis. Their phages were propagated on five different strains of S. epidermidis. Their lytic activity as studied on 561 strains. Phages 336, 392 and 550 had a different host-range and different propagative strains; they typed 93% of the strains susceptible to the 8 phages. The other phages had an activity similar to that of phage 336. Twenty-one per cent of non-epidemic strains were susceptible to at least one of the three phages. The reproducibility, specificity and discriminatory power of these phages suggest they may be a useful addition to previously recognized phages.

When cultivated on solid medium or in stationary liquid medium, most of the 11 studied strains of Bacillus benzoevorans grew as unbranched, flexible, immotile filaments (or trichomes) of undefined length and 1.8 micrometer diameter. They were enclosed in a sheath giving an overall diameter of 3.6 micrometer. When cultivated in vigorously shaken liquid medium, several strains grew as separate rods (1.8 X 2.2 micrometer), did not deform the filament and contained dipicolinic acid. The cytoplasm had a granular aspect due to the presence of poly-beta-hydroxybutyric acid. The Gram reaction was variable but the Gram type was positive. Isolated and purified sheath contained 73% proteins, 12.9% reducing sugars and 8% lipids. In stationary liquid medium, the culture had a mycelial aspect and a thick pellicle formed at the surface. Colonies were circular, flat, opaque, whitish, mat and compact; they had irregular edges, spread out on the surface and did not adhere to the agar.

Formation of toluene in growing cultures of Clostridium aerofoetidum strain WS was enhanced when the medium was supplemented with phenylacetic acid or with L-phenylalanine and L-methionine together. Evidence for the role of L-phenylalanine was shown by the detection of [2H2]-methyl[2,3,4,5,6-2H5]benzene ("heptadeuterotoluene") in growing cultures with L-[2',3',4',5',6'-2H5]phenyl[2,3-2H3]alanine and L-methionine.

Of 320 patients surveyed in a general hospital's medical wards during a 6-month period in 1981, 18 (5.6%) harboured enterobacteria which contained resistance plasmids conferring resistance to trimethoprim (Tp). At the beginning of the study period, Tp-containing therapy was not the first choice for treatment of infections caused by these bacteria and the incidence of plasmid-determined resistance was 10%. When Tp alone was used as the first choice of treatment of urinary tract infections and the use of this antimicrobial was correspondingly increased, the proportion of strains that contained Tp resistance plasmids (R-plasmids) decreased to 4%. Relatively more patients with Tp-resistant strains in the bowel had significant bacteriuria compared with those without Tp-resistant organisms. The continuing occurrence of Tp-R-plasmid containing strains in the gut was associated with continuing antimicrobial therapy; the strains generally disappeared after antimicrobial therapy was stopped.

The eleven strains studied were prototrophic and did not grow in media containing only 1% Bacto-peptone or Bacto-tryptone; they grew rapidly in media containing 0.4% yeast extract and 0.2% sodium acetate or benzoate. The maximal growth temperature ranged from 39 to 45 degrees C. Six aliphatic acids, four aromatic acids and five phenols were used as sole carbon and energy sources by the 11 strains. Carbohydrates and amino acids (except for glycine) were not used as carbon and energy sources. Nitrate (but not nitrite) was used anaerobically as a respiratory electron acceptor. Nitrous oxide was used and reduced to N2 by only 3 strains. The mean guanine-plus-cytosine content of the DNA was 41.3 +/- 1.1 mol %. Morphologically and nutritionally, the bacteria described are clearly different from the 5 known species of the first morphological group whose cells have a diameter greater than 1 micrometer: Bacillus megaterium, B. cereus, B. cereus var. mycoides, B. macroides, B. badius, and B. fastidiosus. Strain B1 (=CCM 3364) is the holotype of Bacillus benzoevorans sp. nov.

The diversity among the phage types of 422 strains of Mycobacterium tuberculosis isolated from patients of different geographical origins suggested that this method might prove useful in studying the propagation of tuberculosis in different types of populations. We first investigated M. tuberculosis strains isolated from France, Portugal, Romania, Algeria, Egypt, Uganda, Mali and India. We then studied in detail two groups of immigrants residing in France, from Portugal and North Africa, respectively. This investigation showed that most patients were suffering from a M. tuberculosis strain with a phage type specific of their country of origin. Factor analysis helped to display phage typing relationships with respect to the geographical origin of patients.