Microbiologia
URI permanente desta comunidadehttps://locus.ufv.br/handle/123456789/11840
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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 Stress enhances the sensitivity of Salmonella enterica serovar Typhimurium to bacteriocins(Journal of Applied Microbiology, 2015-02-19) Galvão, M.F.; Prudêncio, C.V.; Vanetti, M.C.D.The aim of this study was to evaluate the potential application of bacteriocins against Gram-negative bacteria when associated with others food preservation methods. Salmonella was subjected to heat, cold, acid and chemical (with ethylenediaminetetracetate and trisodium phosphate) stresses. Then, the cells were recovered and subjected to treatment with bacteriocins (500 AU ml 1 ) for 6 h. Heat and cold stress were those that promoted more sensitization to bactericidal activity of nisin. Under the same conditions, bovicin HC5 acted more rapidly than nisin reducing the number of viable cells to undetectable levels after 20 min of treatment. Similar results with use of nisin only were observed after 6 h of treatment. Stress conditions used in food industry, such as temperature and pH, and use of chelating agents or membrane disruptors, sensitized Salmonella Typhimurium cells to bacteriocins produced by lactic acid bacteria, such as nisin and bovicin HC5. Food preservation methods sensitized Gram-negative bacteria to bacteriocins activity, which demonstrate the potential of nisin and bovicin HC5 to inhibit the growth of Salmonella.