Microbiologia
URI permanente desta comunidadehttps://locus.ufv.br/handle/123456789/11840
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Resultados da Pesquisa
Item Effect of bovicin HC5 on growth and spore germination of Bacillus cereus and Bacillus thuringiensis isolated from spoiled mango pulp(Journal of Applied Microbiology, 2006-09-27) Carvalho, A.A.T. de; Costa, E.D.; Mantovani, H.C.; Vanetti, M.C.D.Aims: To use bovicin HC5 to inhibit predominant bacteria isolated from spoiled mango pulp.Methods and Results: Bovicin HC5 and nisin were added to brain heart infusion (BHI) medium (40–160 AU ml )1 ) or mango pulp (100 AU ml )1 ) and the growth of Bacillus cereus and Bacillus thuringiensis was monitored. Cultures treated with bovicin HC5 or nisin showed longer lag phases and grew slower in BHI medium. Bovicin HC5 and nisin were bactericidal and showed higher activity in mango pulp at acidic pH values. To determine the effect on spore germination and D values, mango pulp containing bovicin HC5 was inoculated with 10 6 and 10 9 spores per ml )1 , respectively, from each strain tested. Bovicin HC5 reduced the outgrowth of spores from B. cereus and B. thuringiensis, butthermal sensitivity was not affected.Conclusions: Bovicin HC5 was bactericidal against B. cereus and B. thuringien sis isolated from spoiled mango pulp.Significance and Impact of the Study: Bacillus cereus and B. thuringiensis had not been previously isolated from spoiled mango pulp and bovicin HC5 has the potential to inhibit such bacteria in fruit pulps.Item Temperature and pH influence the susceptibility of Salmonella Typhimurium to nisin combined with EDTA(Food Control, 2016-03) Prudêncio, Cláudia Vieira; Mantovani, Hilário Cuquetto; Cecon, Paulo Roberto; Prieto, Miguel; Vanetti, Maria Cristina Dantasantibiotics, such as nisin, generally act on Gram-positive bacteria, whereas Gram-negative bacteria exhibit natural resistance to the action of these bacteriocins. However, Gram-negative bacteria can become susceptible to the action of these antimicrobial peptides with the use of chelating agents, such as EDTA. The activity of bacteriocins can be influenced by several factors, such as environmental conditions and chemical composition of the medium. Moreover, the susceptibility of target microorganism can be altered, due to changes in cellular composition induced by environmental conditions. In this study, we examined the combined effect of variations in temperature and pH on the susceptibility of Salmonella Typhimurium to the action of nisin associated with EDTA. The reduction in the number of viable cells of Salmonella Typhimurium varied according to the temperature and pH, and major reduction in logarithmic cycles of viable cells occurred with a temperature increase. Under low temperature and low pH, a considerable reduction in the viability was also observed after prolonged exposure to bacteriocin, regardless of the presence of EDTA. According to results, temperature and pH conditions influence on the susceptibility of Salmonella Typhimurium to combination of nisin and EDTA and thus should be considered to establish optimal conditions for nisin use.Item Morphological changes in Salmonella Typhimurium caused by the lantibiotic bovicin HC5 in association with EDTA(Annals of Microbiology, 2015-07-03) Prudêncio, Cláudia Vieira; Ferreira, Sukarno Olavo; Mantovani, Hilário Cuquetto; Vanetti, Maria Cristina DantasBacteriocins, particularly those produced by Gram-positive bacteria, have in recent years been considered promising antimicrobial agents to inhibit bacterial growth in food, and thus are potential food preservatives. These peptides generally exhibit a spectrum of action limited to Gram-positive bacteria. However, their action can be extended to Gram-negative bacteria through association with chelating agents. In the present study, we evaluated the occurrence of morphological changes on the cell envelope of Salmonella Typhimurium cells treated with bovicin HC5—a lantibiotic from Streptococcus bovis HC5—in association with EDTA. The morphological changes of the cells were visualized by atomic force microscopy (AFM), and the increase in cell membrane permeability was confirmed by the leakage of potassium ions (K+). The images displayed changes in the cell envelope, with increased surface roughness and a decreased cell volume. These changes indicate that EDTA plays a role in the destabilization of the outer membrane, allowing bovicin HC5 to act on the cytoplasmic membrane through the formation of pores, which was confirmed by the detection of potassium in the cell supernatant. These results suggest that bovicin HC5 combined with EDTA has potential for use on Salmonella cells.Item Strategies for the use of bacteriocins in Gram-negative bacteria: relevance in food microbiology(Journal of Food Science and Technology, 2015-02-01) Prudêncio, Cláudia Vieira; Vanetti, Maria Cristina Dantas; Santos, Miriam Teresinha dosBacteriocins are ribosomally synthesized peptides that have bacteriostatic or bactericidal effects on other bacteria. The use of bacteriocins has emerged as an important strategy to increase food security and to minimize the incidence of foodborne diseases, due to its minimal impact on the nutritional and sensory properties of food products. Gramnegative bacteria are naturally resistant to the action of bacteriocins produced by Gram-positive bacteria, which are widely explored in foods. However, these microorganisms can be sensitized by mild treatments, such as the use of chelating agents, by treatment with plant essential oils or by physical treatments such as heating, freezing or high pressure processing. This sensitization is important in food microbiology, because most pathogens that cause foodborne diseases are Gram-negative bacteria. However, the effectiveness of these treatments is influenced by several factors, such as pH, temperature, the composition of the food and target microbiota. In this review, we comment on the main methods used for the sensitization of Gram-negative bacteria, especially Salmonella, to improve the action of bacteriocins produced by Gram-positive bacteria.Item Differences in the antibacterial activity of nisin and bovicin HC5 against Salmonella Typhimurium under different temperature and pH conditions(Journal of Applied Microbiology, 2014-10-30) Prudencio, C.V.; Mantovani, H.C.; Cecon, P.R.; Vanetti, M.C.D.To compare the action of nisin and bovicin HC5 in combination with EDTA on Salmonella Typhimurium under different environmental conditions. Salmonella Typhimurium was treated in BHI broth containing EDTA (1·5 mmol l−1) and nisin or bovicin HC5 (200 AU ml−1) under different pH and temperature conditions, and according to a central composite design with two factors (temperature and pH). Cell viability was evaluated on plate count agar for 48 h. The combination of nisin or bovicin HC5 with EDTA was able to inhibit the growth of Salmonella, but the temperature and pH conditions promoting inhibition were distinct for each bacteriocin. Nisin was bactericidal over a broad range of temperature and pH, while bovicin HC5 was bacteriostatic in most conditions and bactericidal only in specific conditions (pH >6·0 and temperature >30°C). Salmonella Typhimurium did not show tolerance to bovicin HC5 or cross‐tolerance between these lantibiotics. Nisin and bovicin HC5 both inhibited the growth of Salmonella, but the activity of each bacteriocin was differently influenced by environmental conditions. Nisin and bovicin HC5 have the potential to inhibit the growth of Salmonella, but environmental conditions should be considered to establish optimal conditions for its application.Item Inhibition of Listeria monocytogenes by a lactic acid bacterium isolated from Italian salami(Food Microbiology, 2005-07-18) Carvalho, Ana Andréa Teixeira de; Paula, Rosinéa Aparecida de; Mantovani, Hilário C.; Moraes, Célia Alencar deListeria monocytogenes is an opportunistic psychrotroph foodborne pathogen that has been used as a model organism to study the efficacy of many different preservation methods. This work aimed to test the antilisterial activity of lactic acid bacteria isolated from Italian salami and study the development of resistance. Isolates were obtained from naturally fermented Italian salami and cultures that retained activity in the supernatants after pH neutralization and catalase treatment were further characterized. The isolate showing highest inhibitory activity (PD 6.9) was tested for sensibility to proteases, heat and pH. To evaluate if resistance developed, sensitive strains were transferred with sub-lethal doses of the partially purified inhibitory substance and then inoculated into media containing higher doses of the extract. Isolate PD 6.9 inhibited several L. monocytogenes strains obtained from different origins and retained its activity over a wide range of pH and temperature. When increasing concentrations (10–100 AU ml−1) of the partially purified inhibitory substance were added to culture media, growth of L. monocytogenes did not occur even after 12 h of incubation. Cultures of Listeria that were transferred with sub-lethal doses (10 AU ml−1) of the partially purified inhibitory substance could resist higher doses of the extract (50 AU ml−1), but were inhibited when the concentration was further increased (100 AU ml−1). These results indicate that isolate PD 6.9 could potentially be used as a bioprotective culture for salami fermentation.