Probiotic Lactobacillus fermentum UCO-979C biofilm formation on AGS and Caco-2 cells and Helicobacter pylori inhibition.

The ability of the human isolate Lactobacillus fermentum UCO-979C to form biofilm and synthesize exopolysaccharide on abiotic and biotic models is described. These properties were compared with the well-known Lactobacillus casei Shirota to better understand their anti-Helicobacter pylori probiotic activities. The two strains of lactobacilli synthesized exopolysaccharide as detected by the Dubois method and formed biofilm on abiotic and biotic surfaces visualized by crystal violet staining and scanning electron microscopy. Concomitantly, these strains inhibited H. pylori urease activity by up to 80.4% (strain UCO-979C) and 66.8% (strain Shirota) in gastric adenocarcinoma (AGS) cells, but the two species showed equal levels of inhibition (~84%) in colorectal adenocarcinoma (Caco-2) cells. The results suggest that L. fermentum UCO-979C has probiotic potential against H. pylori infections. However, further analyses are needed to explain the increased activity observed against the pathogen in AGS cells as compared to L. casei Shirota.

Influence of heavy metal supplementation on specific methanogenic activity and microbial communities detected in batch anaerobic digesters.

Natural and modified zeolites (0.5-1.0 mm) from the Tasajera deposit in Cuba were used to enhance the anaerobic digestion process of synthetic substrates. Natural zeolites were modified by ionic exchange and by adsorption with nickel, cobalt and magnesium. The experiments were carried out by using an inoculum from a full-scale anaerobic reactor treating winery wastewater. Modified natural zeolites not only enhanced the anaerobic digestion process, but also increased the specific methanogenic activity (SMA) of the sludges. The textural and chemical surface characteristics of the modified zeolites were related to the process performance, volatile fatty acid (VFA) production and microbial communities found in the digesters. For the selected dose of modified zeolites [0.05 g/g of volatile suspended solids (VSS)], the lowest concentration was found for cobalt followed by nickel and magnesium. Based on the analyses of anaerobic biofilms, the heavy metal incorporated into the zeolite was shown to have a great influence on the predominance of species. For example, the presence of nickel and cobalt favoured Methanosaeta, while at the same dose magnesic zeolite stimulated the presence of Methanosarcina and sulfate-reducing bacteria (SRB). In digesters with modified zeolites and metal supplementations the values of SMA were higher than those obtained in the control and natural zeolite digesters.

Molecular analysis of the community structure of nitrifying bacteria in a continuous-flow bioreactor.

We herein report the diversity and relative abundance of chemolithotrophic nitrifying bacteria in a continuous-flow bioreactor using 16S-ribosomal RNA quantitative dot-blot hybridizations. About 14.9% of the total bacterial population, determined by epifluorescence microscopy in the bioreactor suspended phase, was represented by nitrifying bacteria. Of this fraction, ammonia- and nitrite-oxidizing bacteria accounted for 10% and 90%, respectively, the latter group being mostly Nitrospira-like. On the other hand, the nitrifiers adhesion/colonization capacity on polyethylene surfaces as evaluated by scanning electron microscopy and hybridizations analyses was 12.6% of the total bacterial community adhered. Finally, in spite of the relatively small contribution of nitrifiers to the total bacterial abundance in the bioreactor, we determined a mean ammonia removal rate of 170.48 +/- 8.29 mg N l(-1) d(-1); thus, the low percentage of ammonia-oxidizing bacteria, was not limiting the bioreactor performance.

Resistencia de streptococcus pneumoniae a penicilina y su asociación con factores clínicos y epidemiológicos / Resistance of streptococcus pneumoniae to penicillin: clinical and epidemiological aspects

Background: Penicillin and third generation cephalosporin resistant pneumococcal isolates have emerged in Chile, mainly in the pediatric population. These isolates complicate therapeutic alternatives, specially among patients with central nervous system infections. Aim: To assess the frequency of penicillin and third generation cephalosporin resistance among isolates obtained from pediatric patients with invasive pneumococcal infections, and to study serotypes and clinical risk factors associated with resistance. Material and methods: Microbiological isolates obtained from children between April 1994 and May 1999 with pneumococcal invasive infections, were serotyped and analyzed according to their susceptibility to penicillin and cefotaxime by E-test and broth microdilution testing. Potential risk factors studied included patient's age, previous antibiotic use or admissions, comorbidity, and serotypes. Results: Seventy eight patients were studied. Penicillin-resistant pneumococcal isolates were detected in 35.9 percent of cases (21.8 percent with intermediate and 14.1 percent with high level resistance) without significant variation among different clinical conditions. Most of the high level penicillin-resistant pneumoccocal isolates had MIC ü4 µg/mL (8 out of 11 strains). One third of penicillin-resistant isolates also expressed cefotaxime resistance. Multivariate analysis indicated an age ²36 months (OR=6.8; IC 95 percent: 1.4 to 33.5) and serotype 14 (OR=6.3; IC 95 percent: 1.7 to 23.3) as factors associated with penicillin resistance. Conclusions: One third of the invasive pneumococcal isolates obtained from pediatric patients were resistant to penicillin. Risk factors involved a younger age and pneumococcal isolates belonging to serotype 14

Análisis comparativo de la adherencia in vitro de bacterias bucales a materiales de restauración y prótesis / Comparative analysis of the adherence in vitro of oral bateria to the prosthesis and restorative dental materials

Se realizó un trabajo de investigación in vitro para determinar el grado de adherencia de los microorganismos de la flora bucal a ciertos materiales dentales de obturación y de prótesis. Los materiales usados fueron: amalgama, resinas compuestas de fotocurado, vidrio ionómero y acrílico de termopolimerización, fabricándose 40 probetas con cada uno de estos materiales, de estas 40 probetas de cada material, el 50 por ciento de ellas tenían la superficie pulida y el otro 50 por ciento, la superficie no-pulida, con el fin de determinar cómo afecta a la adherencia microbiana el estado de la superficie del material. Los microorganismos utilizados fueron una cepa de S. mutans, obtenida en el Laboratorio de Microbiología de la escuela Dental de la Universidad de Chile, y que cumplía con todas las pruebas bioquímicas; una cepa de C. albicans caracterizada (LR00/18b); la Flora Aerobia Total fue proporcionada por la saliva de un individuo de 27 años, clínicamente sano. La Flora Aerobia Facultativa y Anaerobia Aerotolerante, se obtuvo de un saco periodontal de un paciente de 51 años, de la clínica de Periodoncia de la Escuela Dental de la Universidad de Chile, el que presentaba Periodontitis del Adulto. Los medios cultivos utilizados en la investigación fueron: Caldo TYCSB, para el S. mutans, Caldo Sabureaud + Cloranfenicol, para C. albicans, Caldo Cerebro Corazón, para la Flora Aerobia, Caldo Cerebro Corazón + Thioglicolato, para los Aerobios Facultativos y Anaerobios Aerotolerantes. SE sembraron los medios de cultivo, con los microorganismos correspondientes a cada uno de ellos y luego, se colocaron 5 probetas pulidas y 5 no-pulidas, en 10 tubos de cada medio de cultivo, llevándose estas siembras al incubador, a tiempos variables para cada tipo de microorganismos. Posteriormente, se sacaron las probetas y se agitaron en suero fisiológico estéril, para desprender las colonias microbianas no adheridas, luego se montaron con plasticina, en una placa de Petri y se contaron las colonias de las superficies operativas, con una lupa Zeiss Stemi 2000

Co-occurrence of non-toxic (cyanopeptolin) and toxic (microcystin) peptides in a bloom of Microcystis sp. from a Chilean lake.

A cyanobacterial bloom occurring in 1998 in lake Tres Pascualas (Concepción/Chile) was found to be dominated by Microcystis sp. The bloom contained both non-toxic (cyanopeptolin-type) and hepatotoxic (microcystin-type) peptides. Cyanopeptolin structure of the non-toxic peptides (called cyanopeptolin VW-1 and VW-2, respectively) was revealed by matrix assisted laser desorption ionization mass spectrometry (MALDI-TOF-MS) of whole cells, showing dominant molecular ions at m/z = 975 and m/z 995, respectively. On post source decay (PSD), both cyanopeptolins showed fragments deriving from Ahp-Phe-MTyr (3-amino-6-hydroxy-2-piperidone), the characteristic partial structure of cyanopeptolins. The amounts of each of the two cyanopeptolins could only roughly be estimated to be >0.1% of bloom material dry weight. In addition the blooms contained microcystins (20 microg/g bloom dry weight as determined by RP-HPLC, 13 microg/g according to ELISA determination). MALDI-TOF-MS revealed several structural variants of microcystin: MCYST-RR (microcystin with Arg and Arg, indicated by m/z 1,038 and confirmed by PSD revealing a m/z = 135 fragment deriving from the Adda side chain, MCYST-FR (microcystin with Phe and Arg, indicated by m/z = 1,015). The presence of [Asp(3)]-MCYST-LR (microcystin with Leu and Arg, Asp non-methylated, indicated by m/z 981), and [Asp(3)]-MCYST-YR (microcystin with Tyr and Arg, Asp non-methylated, indicated by m/z 1,031) were likely. The relative amounts of the peptides varied between February, April, and May. Whole cell extracts from the bloom material revealed specific enzyme inhibitory activities. The serin-proteases trypsin, plasmin, elastase were inhibited, assumable due to the cyanopeptolins found. Elastase and the cysteine-protease papain were not inhibited, inhibitions of protein kinase and glutathione S-transferase (GST) were low. Strong inhibition was observed with protein-phosphatase-1, likely due to the microcystins present in the samples.

Microcystin in cyanobacterial blooms in a Chilean lake.

Cyanobacterial blooms dominated by Microcystis sp. occurred in lake Rocuant ("marisma", near Concepción/Chile) in February 1995 and 1996. In the bloom samples collected in both years the hepatotoxin microcystin was detected by RP-HPLC in both samples and in the sample of 1995 also by a toxicity assay using primary rat hepatocytes. In the bloom of 1995, the microcystin content of the dry bloom biomass was determined to be 130 micrograms/g on the basis of the RP-HPLC peak area and 800 micrograms/g on the basis of the rat hepatotoxicity assay, respectively. In the bloom of 1996, RP-HPLC analysis revealed a microcystin content of 8.13 micrograms/g bloom material dry weight. In this year no hepatotoxicity was measured using a concentration range up to 0.8 mg (d. w.) of bloom material per ml in the rat hepatotoxicity assay. This is the first report on the detection of microcystins in Chilean water bodies.

Growth of methylaminotrophic, acetotrophic and hydrogenotrophic methanogenic bacteria on artificial supports.

The efficiency of organic matter degradation in attached biomass reactors depends on the suitable selection of artificial support for the retention of bacterial communities. We have studied the growth on glass and clay beads of methylaminotrophic, acetotrophic and hydrogenotrophic methanogenic bacterial communities isolated from anaerobic reactors. Bacterial counts were performed by the standard MPN technique. Experiments were performed in 50 ml vials for 12 days at 35 degrees C. Increase in the counts of methylaminotrophic and hydrogenotrophic methanogens occurred on both glass and clay beads. The latter support material also stimulated the growth rate of methylaminotrophic methanogens.

Effect of imipenem and sulbactam on sessile cells of Acinetobacter baumannii growing in biofilm.

The effect of the age of biofilms formed by Acinetobacter baumannii on the activity of sulbactam and imipenem on sessile cells was investigated. Against cells of young biofilms both antibiotics were rapidly bactericidal. As the biofilm aged, sulbactam lost most of its activity, but imipenem continued to be bactericidal to some extent. This fact probably reflects the ability of imipenem to exert bactericidal activity on slow-growing bacteria.

Biofilm formation by Acinetobacter baumannii.

Acinetobacter baumannii, an important nosocomial pathogen is usually found on various surfaces in the hospital environment. In this work, the ability to form biofilms on the surface of sterile coverslips by one clinical isolate of A. baumannii was studied. Sessile cells which adhered to coverslips after being immersed in a nutrient-deficient mineral medium were observed by epifluorescence and scanning electron microscopy at various times of incubation. A rapid increase in the number of sessile cells in young biofilms, followed by a slower increase of such cells was found. At 48 h biofilms were clearly visible and an amorphous material similar to the exopolysaccharide described in some other bacteria covered sessile cells was evident. Biofilm formation by A. baumannii probably favours its maintenance on solid surfaces in the hospital environment and protects the micro-organism against some antibacterial factors.

[Bacteriologic profile of the Andalien estuary (Chile). Count, biomass, and productivity]. / Perfil bacteriológico del estuario Andalién (Chile). Recuento, biomasa y productividad.

Bacterial population, biomass and productivity from the Andalien estuary (Concepción, Chile) were investigated by measuring the viable counts and the total cell population by epifluorescence. There were differences in the viable counts obtained during fall and spring, but not in total counts. The bacterial productivity in the estuary and the nearest sea was increased during the spring, probably due to a larger proportion of metabolic active cells. The results also suggest an increased bacterial activity in the estuary and the nearest sea for the spring time.

[Dyserythropoietic congenital anemia type II with intensive hepatic hemosiderosis in a 1-month-old infant]. / Anemia diseritropoyética congénita tipo II con intensa hemosiderosis hepática en un lactante de un mes.

A case of dyserythropoietic congenital anemia type II (HEMPAS) in an infant 35 days of age is reported. Diagnosis was based upon morphological features of the erythroblasts, 25% of them were bi or multinucleated and a positive acidified serum test (pseudo HAM). The early and severe anemia which was present from the first days of life is emphasized. An additional and significant hemolytic factor with a relative tocopherol deficiency is suggested. A very important degree of hepatic hemosiderosis was found at necropsy. This finding reveals the very active dyserytropietic disorder in this case from the beginning of intrauterine file.