Avaliação da susceptibilidade e resistência bacteriana aos agentes controladores do crescimento de uso hospitalar e industrial / Bacterial susceptibility and resistance to growth controlling agents in hospital and industrial use

O presente trabalho tem como objetivo estudar o comportamento e a resistência de bactérias em relação a agentes químicos com ação antimicrobiana em diferentes concentrações e determinar a quantidade mínina para que ocorra a inibição dos microrganismos. Serratia marcescens, Proteus mirabilis, Pseudomonas aeruginosas, Escherichia coli, Bacillus cereus e Staphylococcus aureus, foram os microrganismos utilizados, os quais foram semeados em meio Plate Count Agar (PCA). Na sequência, aplicaram-se os testes com os agentes controladores, nas concentrações de 0,5 %, 1,5%, 3,0%, 5,0%, 7,0% e 10,0 %, e os álcoois pré-determinados. A identificação da eficácia foi definida atraves frequência e índice de inibição. Foram realizadas análises de 13 substâncias nas seis diferentes concentrações, ou seja, 468 amostras totalizadas no experimento. Com relação aos microrganismos estudados observou-se, dentre os componentes escolhidos, uma ampla resistência, mesmo em concentrações maiores. O estudo demonstrou variação de resistência e sensibilidade, sendo ácido ascórbico o agente com a maior concentração inibitória mínima e as menores concentrações foram do peróxido de hidrogênio. Considerando importância do uso desses compostos na inibição e no controle de agentes bacterianos em diferentes áreas, torna-se vital o conhecimento da amplitude de seu espectro, assim, alguns produtos, nas diluições recomendadas para uso, revelaram possuir atividade antibacteriana mais reduzida ou inexistente.

The present work aims at studying the behavior and bacteria resistance against chemical agents with antimicrobial action in different concentrations and determining the minimum quantity for micro-organism inhibition. This study used Serratia marcescens, Proteus mirabilis, Pseudomonas aeruginosa, Escherichia coli, Bacillus cereus and Staphylococcus aureus micro-organisms, which were seeded in Plate Count Agar (PCA) medium. After, the tests were applied with controlling agents, at concentrations of 0.5%, 1.5%, 3.0%, 5.0%, 7.0% and 10.0%, and predetermined alcohols. Effectiveness was identified by frequency and inhibition index. Analyses were carried out on 13 substances in six different concentrations, i.e., a total of 468 samples in the experiment. In relation to the studied micro-organism, a broad resistance could be observed among the chosen components, even in larger concentrations. The study presented resistance and sensitivity variation, with ascorbic acid being the agent with the greatest minimum inhibitory concentration, while hydrogen peroxide presented the lowest concentrations. Considering the importance of these compounds in inhibiting and controlling bacterial agents in different areas, it is vital to expand the knowledge on the broadness of its spectrum, since some of the products, at the recommended use dilutions, presented low or non-existent antibacterial activity.

Geochemistry of ultra-fine and nano-compounds in coal gasification ashes: a synoptic view.

The nano-mineralogy, petrology, and chemistry of coal gasification products have not been studied as extensively as the products of the more widely used pulverized-coal combustion. The solid residues from the gasification of a low- to medium-sulfur, inertinite-rich, volatile A bituminous coal, and a high sulfur, vitrinite-rich, volatile C bituminous coal were investigated. Multifaceted chemical characterization by XRD, Raman spectroscopy, petrology, FE-SEM/EDS, and HR-TEM/SEAD/FFT/EDS provided an in-depth understanding of coal gasification ash-forming processes. The petrology of the residues generally reflected the rank and maceral composition of the feed coals, with the higher rank, high-inertinite coal having anisotropic carbons and inertinite in the residue, and the lower rank coal-derived residue containing isotropic carbons. The feed coal chemistry determines the mineralogy of the non-glass, non-carbon portions of the residues, with the proportions of CaCO3 versus Al2O3 determining the tendency towards the neoformation of anorthite versus mullite, respectively. Electron beam studies showed the presence of a number of potentially hazardous elements in nanoparticles. Some of the neoformed ultra-fine/nano-minerals found in the coal ashes are the same as those commonly associated with oxidation/transformation of sulfides and sulfates.

Inhibition of Listeria monocytogenes in dairy products using the bacteriocin-like peptide cerein 8A.

The efficacy of the antimicrobial peptide cerein 8A to control the development of Listeria monocytogenes in milk and soft cheese was investigated. The addition of 160 AU ml(-1) cerein 8A to UHT milk resulted in a decrease of 3 log cycles in viable cells within the 14-day period at 4 degrees C. The viable counts of L. monocytogenes in pasteurized milk samples containing cerein 8A was lower than those observed in controls without bacteriocin. Addition of cerein 8A to Minas-type soft cheese caused a delay in the start of exponential growth phase, although similar counts were observed after day 6. When cerein 8A was used to control cheese surface contamination by L. monocytogenes, a decrease of 2 log cycles in viable counts of cerein-treated samples was observed during 30 days at 4 degrees C. This antimicrobial peptide shows potential use as a biopreservative for application in dairy products.

Characterization of a bacteriocin-like substance produced by Bacillus amyloliquefaciens isolated from the Brazilian Atlantic forest.

A Bacillus strain producing a bacteriocin-like substance was characterized by biochemical profiling and 16S rDNA sequencing. Phylogenetic analysis indicated that the strain has high sequence similarity with Bacillus amyloliquefaciens. The antimicrobial substance was inhibitory to pathogenic and food-spoilage bacteria, such as Listeria monocytogenes, Bacillus cereus, Serratia marcescens, and Pasteurella haemolytica. It was stable over a wide temperature range, but lost activity when the temperature reached 121 degrees C/15 min. Maximum activity was observed at acidic and neutral pH values, but not at alkaline pH. The antimicrobial substance was sensitive to the proteolytic action of trypsin, papain, proteinase K, and pronase E. Except for iturins, other antimicrobial peptides have not been described for B. amyloliquefaciens. The identification of a bacteriocin-like inhibitory substance active against L. monocytogenes addresses an important aspect of food protection.

Characterization of a bacteriocin-like substance produced by Bacillus amyloliquefaciens isolated from the Brazilian Atlantic forest / Caracterización de una substancia del tipo bacteriocina producida por Bacillus amyloliquefaciens aislado del bosque atlántico brasileño

A Bacillus strain producing a bacteriocin-like substance was characterized by biochemical profiling and 16S rDNA sequencing. Phylogenetic analysis indicated that the strain has high sequence similarity with Bacillus amyloliquefaciens. The antimicrobial substance was inhibitory to pathogenic and food-spoilage bacteria, such as Listeria monocytogenes, Bacillus cereus, Serratia marcescens, and Pasteurella haemolytica. It was stable over a wide temperature range, but lost activity when the temperature reached 121 degrees C/15 min. Maximum activity was observed at acidic and neutral pH values, but not at alkaline pH. The antimicrobial substance was sensitive to the proteolytic action of trypsin, papain, proteinase K, and pronase E. Except for iturins, other antimicrobial peptides have not been described for B. amyloliquefaciens. The identification of a bacteriocin-like inhibitory substance active against L. monocytogenes addresses an important aspect of food protection (AU)

Se ha caracterizado una cepa de Bacillus productora de una substancia del tipo bacteriocina mediante perfiles bioquímicos y secuenciación del rDNA 16S. El análisis filogenético indicó que la cepa presentaba una gran similitud de secuencia con Bacillus amylolique faciens. La sustancia antimicrobiana era inhibitoria para algunas bacterias patógenas y causantes del deterioro de los alimentos como Listeria monocytogenes, Bacillus cereus, Serrati amarcescens y Pasteurella haemolytica. La sustancia era estable en una amplia gama de temperaturas, pero perdía la actividad cuando la temperatura alcanzaba 121°C/15 min. La actividad máxima fue observada a valores de pH ácidos y neutros, pero no a pH alcalinos. La sustancia antimicrobiana era sensible a la acción proteolítica de la tripsina, la papaína, la proteinasa K y la pronasa E. Excepto las iturinaos, no se han descrito otros péptidos antimicrobianos de B. amyloliquefaciens. La identificación de una sustancia tipo bacteriocina activa contra L. monocytogenes cubre un aspecto importante en la protección de los alimentos (AU)

Antibacterial activity of cerein 8A, a bacteriocin-like peptide produced by Bacillus cereus.

The mode of action of cerein 8A, a bacteriocin produced by the soil bacterium Bacillus cereus 8A, was investigated. The effect of cerein 8A was tested against Listeria monocytogenes and a bactericidal effect at 400 arbitrary units (AU)/ml was observed. In addition, cerein 8A was bactericidal against Bacillus cereus at 200 AU/ml, and inhibited the growth of Escherichia coli and Salmonella Enteritidis. Stronger inhibition of these gram-negative bacteria was achieved when the chelating agent EDTA was added together with bacteriocin. The effect of cerein 8A on B. cereus and L. monocytogenes was also investigated by Fourier transform infrared spectroscopy (FTIR). Treated cells had an important frequency increase at 2920 cm-1 and a decrease at 1400 cm-1, corresponding to assignments of fatty acids. Transmission electron microscopy showed damaged cell walls and loss of protoplasmic material. These results suggest that the mode of action of cerein 8A is to interfere with cell membranes and the cell wall.

Antibacterial activity of cerein 8A, a bacteriocin-like peptide produced by Bacillus cereus / Actividad antibacteriana de la cereína 8A, un péptido de tipo bacteriocina producido por Bacillus cereus

The mode of action of cerein 8A, a bacteriocin produced by the soil bacterium Bacillus cereus 8A, was investigated. The effect of cerein 8A was tested against Listeria monocytogenes and a bactericidal effect at 400 arbitrary units (AU)/ml was observed. In addition, cerein 8A was bactericidal against Bacillus cereus at 200 AU/ml, and inhibited the growth of Escherichia coli and Salmonella Enteritidis. Stronger inhibition of these gram-negative bacteria was achieved when the chelating agent EDTA was added together with bacteriocin. The effect of cerein 8A on B. cereus and L. monocytogenes was also investigated by Fourier transform infrared spectroscopy (FTIR). Treated cells had an important frequency increase at 2920 cm-1 and a decrease at 1400 cm-1, corresponding to assignments of fatty acids. Transmission electron microscopy showed damaged cell walls and loss of protoplasmic material. These results suggest that the mode of action of cerein 8A is to interfere with cell membranes and the cell wall (AU)

Se investigó el modo de acción de la cereína 8A, una bacteriocina producida por la bacteria del suelo Bacillus cereus 8A. El efecto de la cereína 8A fue probado contra Listeria monocytogenes, obteniendo un efecto bactericida a concentraciones de 400 unidades arbitrarias (AU)/ml. La cereína 8A también tuvo un efecto bactericida contra Bacillus cereus a una concentración de 200 AU/ml. La bacteriocina inhibió el crecimiento de Escherichia coli y Salmonella Enteritidis. Mayor inhibición contra estas bacterias gram-negativas se consiguió cuando a la bacteriocina se le añadió el agente quelante EDTA. El efecto de la cereína 8A sobre B. cereus y L. monocytogenes también fue investigado por espectroscopía de infrarrojos de transformación de Fourier (FTIR). Las células tratadas mostraron un importante crecimiento en frecuencia de 2920 cm-1 y un decrecimiento de 1400 cm-1 de banda, correspondiéndose con la asignación de los ácidos grasos. La microscopía electrónica de transmisión mostró que las células habían padecido daños en la pared celular, con pérdida de material protoplásmico. Los resultados sugieren que el modo de acción de la cereína 8A se produce mediante su intervención en las membranas celulares y en la pared celular (AU)

Antimicrobial susceptibility, hemolysis, and hemagglutination among aeromonas ssp. isolated from water of a bovine abattoir

The presence of Aeromonas ssp. in food has been demonstrated. They are often introduced from water, which is the natural habitat of many species and is thought to be the main source of contamination. The occurrence of Aeromonas ssp. was investigated in 70 water samples of a bovine abattoir. Aeromonas ssp. were present in 21.4(per cent) of water samples. A.hydrophila was isolated from 11.4(per cent) of supplying water samples and from 25.7(per cent) of the water drained from carcasses, whereas A. sobria was sole isolated from 5.7(per cent) of supplying water samples. Although greater number of positive samples were from water drained from carcasses, only A.hydrophila isolates were present. This suggests that the supplying water is the source of contamination. The antibiotic susceptibility testing revealed all strains were resistant to ß-lactam antibiotics. However, the susceptibility to other antimicrobials was variable, being A.hydrophila more resistant than A. sobria strains. The investigation for virulence factors revealed positive reactions of hemolysis and hemagglutination. The results indicate that Aeromonas ssp. are present in the supplying water system. These microorganisms may be a potential contaminant of carcasses and widespread in derived food.