Revista de la Asociacion Argentina de Microbiologia最新文献

A comparative study of the citrate synthases purified from the facultatively photosynthetic bacterium Rhodospirillum rubrum (Gram negative) and the thermophile Bacillus stearothermophilus (Gram positive) was made. The citrate synthase from R. rubrum was activated by KCl (6-fold at 0.1 M KCl) and, less effectively, by NaCl and NH4Cl. Its molecular weight was about 300,000. The enzyme was strongly inhibited by NADH, and this inhibition was counteracted by AMP. The citrate synthase from B. stearothermophilus was little affected by KCl, NaCl and NH4Cl, all of which activated by about 25% at 0.1 M. Its molecular weight was ca 100,000. The enzyme was not affected by NADH or AMP. Both citrate synthases were insensitive to alpah-oxoglutarate concentrations up to 5 mM, and were inhibited by ATP; the B. stearothermophilus enzyme was more strongly inhibited than the R. rubrum enzyme. In both cases the ATP inhibition was strictly competitive towards acetyl-CoA and non-competitive towards oxaloacetate. Both enzymes, in spite of the peculiar physiological properties of their bacterial sources, followed the close correlation between the properties of the citrate synthase and the taxonomical position of the microorganism, proposed by Weitzman and his co-workers.

A comparative study of serologic cross-reactions between histoplasmosis and paracoccidioidomycosis was carried out using complement fixation (CF) and agar gel immunodiffusion (ID) tests. Sera from 77 patients with paracoccidioidomycosis, 38 with histoplasmosis and 50 healthy individuals were studied. The Pan American Health Organization microtiter CF test and the Hupper ID technique were employed. The antigens were prepared by the method of Ajello as modified by Negroni. Paracoccidioidin CF test was positive in all patients with paracoccidioidomycosis; 29 of these (37%) presented serologic cross-reaction with histoplasmin. Histoplasmin CF test was positive in all but one of the patients with histoplasmosis and only 4 of them (10%) showed cross-reaction with paracoccidioidin. Positive reactions with the ID test were registered in 74/77 cases of paracoccidiodomycosis, with only one case of cross-reaction (1,3%). The result for the ID test was positive in all but one of the cases of histoplasmosis, with only one cross-reaction with paracoccidiodin (2,7%). The ID test seemed to be much more specific although it could be less sensitive. It was also easier to perform and less expensive than the CF test. Nevertheless the authors urge that the CF test also be carried out whenever posible, since the information obtained is likely to be of more value in follow-up and control of patients.

Human teeth were suspended in a basal medium with sucrose 10%; they were incudated for formation of dental plaques "in vitro". The microorganisms used were: Strep. mutans, Lactobacillus salivarius var. salivarius and a mixture of them. The following aspects were stablishad by scanning electron microscopy: 1) The teeth inoculated with Strep. mutans had coccoid forms, lying on an organic film with spheric spaces in some sectors, and irreguar forms in others (Fig. 1). 2) The teeth inoculated with Lactobacillus salivarius had rod forms attached to the adamantine surface (Fig. 2, 3). 3) Teeth incubated with the mixutre had rod forms over a granular film (Fig. 4). 4) The control teath did not have plaque (Fig. 5). This experience shows that the extracellular polisacharide, reticulated or granular (mutano) appeared only in teeth incubated with Strep. mutans alone (Fig. 1) or mixed with Lactobacillus (Fig. 4). On the other hand Lactobacillus appeared attached on the enamel surfaces, perhaps due to cohesive adhesive forces (Fig. 2). Two different interpretation or the formation of dental plaques that take place on the enamel free surfaces of teeth are presented.

The SM-3 mutant of Salmonella typhimurium was isolated as streptomycin resistant and temperature conditional thiamine auxotroph. At 37 C it required thiamine, although it behaves as a leaky mutant at this temperature in minimal liquid medium. At 30 degrees C it was able to growth without thiamine. In minimal-glucose-aminoacids at 37 C after an initial growth, cellular lysis occurred. The same happened with other hexoses, but it was not observable when glycerol or lactate were used as carbon source. Microscopic examination showed clumps of cellular debris, empty bagshapes and swelling of microorganisms, suggesting a cell wall defect. Sucrose 0.5 M protected SM-3 cells from osmotic fragility. At 30 C growth was normal and at 37 C in presence of exogenous thiamine full growth without bacteriolysis was obtained. Preliminary experiments of bacterial conjugation allowed the identification of a new locus involved in thiamine biosynthesis which was tentatively mapped in the pur A - pro B region of the chromosomal map of S. typhimurium.

To study the virucidal activity of several chemical agents available locally in Argentina for rabies virus, was considered to be very useful for physicians treating persons bitten by rabid dogs and for those responsible for the sterilization of rabies contaminated areas. CVS fixed rabies virus suspensions were treated for one minute at room temperature with soaps of different quality, anionic (most of them derivates of dodecyl-bencene-sulfonic acid) and cationic (dodecyl, tetradecyl, hexadecyl-trimethyl-ammonium bromide) detergents, lemon juice, vinegar, hydrochloric acid, sodium carbonate, etc. Most of these agents inactivated 4 logarithms of virus (99.99%) which is approximately the amount of virus present in the saliva of experimentally infected dogs. It is noteworthy that a popular treatment for animal bites in several latin America countries is lemon juice, while the scientific community may still recommend the use of nitric acid which has a definitive necrotic and scarring effect on the treated wound. The need to eliminate organic matter prior to sterilization of contaminated areas because of interference with the virucidal activity of the agents was also confirmed.

Psychophilic microorganisms, able to grow at 0-1 degrees C, were isolated from water obtained from the Paraná River at Rosario. One of the strains, R-12, was identified as Pseudomonas fluorescens according to the description in Bergey's Manual of Determinative Bacteriology (8th Ed., 1974). The microorganism was able to grow in liquid minimal medium with glucose, acetate, glutamate or casein hydrolysate as sole carbon source, at 20 degrees C. The enzymes of the Entner-Doudoroff pathway were induced in cells grown on glucose. The Krebs cycle was apparently operative in all cases; the lower levels of citrate synthase and isocitrate dehydrogenase were found in glucose-grown cells. Isocitrate lyase was present at a high concentration, and malate synthase considerably increased, in acetate-grown cells, thus suggesting the operation of the glyoxylate cycle. When cells were grown on glucose the anaplerotic function was probably fulfilled by pyruvate carboxylase, although phosphoenolpyruvate carboxylase was also present. The gluconeogenic enzyme phosphoenolpyruvate carboxykinase was repressed by glucose; malic enzyme was repressed by acetate. The regulatory patterns shown by citrate synthase and pyruvate carboxylase were similar to those described for the enzymes from other Pseudomonas. Whole cells of the R-12 strain were able to decarboxylate the aminoacids serine, aspartate and glutamate. Aspartate aminotransferase was present at high levels in aminoacid-grown cells, thus suggesting a catabolic role, whereas glutamate dehydrogenase had increased levels in glucose - or acetate-grown cells, suggesting that it fulfilled a mainly biosynthetic role.

The immunological competence of eleven patients with undetermined leprosy was compared with that of ten normal volunteers of the same age and sex distribution; these controls have not had previous contact with leprosy. The following parameters were studied in peripheral blood cells: 1) percentage of lymphocyte bearing surface immunoglobulins, as revealed by immunofluorescence; 2) percentage of lymphocyte bearing complement receptors, as studied by antibody and complement coated erithrocyte rosetting; 3) percentage of T cells, as revealed by spontaneous sheep erithrocyte rosettes; 4) blastogenic and mytogenic response of cultured lymphocytes to PHA and 5) cell migration inhibition test using lepromine (80 x 10(6) bacilli/ml) as antigen. Skin reactions to lepromine were also assayed. In the six lepromine-positive patients with undetermined leprosy, no major immunological alterations could be detected. On the contrary, the five lepromine-negative patients showed important alterations which could well be considered as precursors of lepromatous leprosy.

In 731 diarrhea cases studied from January 1971 to June 1973 in Tucumán a significant increase of shigellosis in eutrophic children was observed. The frequency of Shigella isolations, considering all the enteropathogens found, were: 15,5 %; 13 % and 21,3 % in 1971, 1972 and 1973, respectively (Table 1). All the strains of Shigella isolated belonged to the Shigella flexneri B or Shigella sonnei D groups, being the percentage for the former 78 % in 1971; 93 % in 1972 and 77 % in 1973 (Table 2). The age distribution of patients with shigellosis is shown in Table 3, the 87,7 % occurring within the first 3 years of life. S. flexneri B and S. sonnei D strains showed similar sensitivity to nalidixic acid, cephalosporines, chloramphenicol and trimethoprim plus sulfametoxazol; S. flexneri B was more susceptible to rifampicin, although this antibiotic was not used for therapeutics. A different sensitivity to kanamicin was observed being S. flexneri B, less susceptible than S. sonnei D, (Table 4). Fifty five percent of the cases showed clinical improvement after 48 h. of starting antibiotic treatment; 80 % after 72 h. and only 20 % required 96 or more for significant recovery. Although the number of patients with some degree of malnutrition was small, 7 out of the 8 cases studied required 72 h. or more for recovery.