The aim of this study was to evaluate the growth kinetics of Listeria innocua Serovar 6a (CECT 910) and Listeria monocytogenes Serovar 4b (CECT 4032) exposed to combinations of carvacrol and citral (0.0 μL/mL (control), 0.050 μL/mL of carvacrol and 0.075 μL/mL of citral, 0.050 μL/mL of carvacrol and 0.125 μL/mL of citral, 0.085 μL/mL of carvacrol and 0.075 μL/mL of citral, and 0.085 μL/mL of carvacrol and 0.125 μL/mL of citral), with two initial inoculum concentrations, and also the occurrence of sublethal damage in these cell populations. The terpene combinations exhibited antibacterial activity against L. innocua and L. monocytogenes and the effects were dependent on the concentration of terpenes present in the culture medium (p ≤ 0.05). When terpene-treated L. innocua and L. monocytogenes were incubated in TSB, significant differences in lag phase and growth rate were observed between low and high inoculum concentrations (p ≤ 0.05), indicating that the inoculum level should be taken into account in modeling studies. When bacterial cells were exposed to terpenes the proportion of sublethally injured cells increased with the increase in the terpene dose (p ≤ 0.05). In conclusion, all of these results show that carvacrol and citral can be used in combination at 25% of the MIC in order to control Listeria growth.

The aim of this study was to evaluate the antibiotic susceptibility of Listeria innocua (L.innocua) and Listeria monocytogenes (L.monocytogenes) cells in the presence of citral and carvacrol at sublethal concentrations in an agar medium. The presence of terpenes in the L.monocytogenes and L.innocua culture medium provided a reduction in the minimal inhibitory concentration (MIC) of all the antibiotics tested. These effects were dependent on the concentration of terpenes present in the culture medium. The combination of citral and carvacrol potentiated antibiotic activity by reducing the MIC values of bacitracin and colistin from 32 center dot 0 and 128 center dot 0 mu gml(-1) to 1 center dot 0 and 2 center dot 0 mu gml(-1), respectively. Thus, both Listeria species became more susceptible to these drugs. In this way, the colistin and bacitracin resistance of L.monocytogenes and L.innocua was reversed in the presence of terpenes. Results obtained in this study show that the phytochemicals citral and carvacrol potentiate antibiotic activity, reducing the MIC values of cultured L.monocytogenes and L.innocua.Significance and Impact of the StudyPhytochemicals citral and carvacrol potentiate antibiotic activity of erythromycin, bacitracin and colistin by reducing the MIC values of cultured Listeriamonocytogenes and Listeria innocua. This effect in reducing the MIC values of the antibiotics tested in both micro-organisms was increased when natural antimicrobials were combined. This finding indicated that the combination among terpenes and antibiotic may contribute in reducing the required dosage of antibiotics due to the possible effect of terpenes on permeation barrier of the micro-organism cell membrane.

The aim of this work was to compare the growth kinetics of Listeria innocua and Listeria monocytogenes serovar 4b exposed to carvacrol, considering two initial inoculum sizes, and the occurrence of sublethal damage in these cell populations, by plating them in selective and non-selective medium. Bacteria were grown in TSB supplemented with carvacrol: 0.0 mu L/mL (control), 0.100 mu L/mL and 0.175 mu L/mL. The increase in carvacrol concentration resulted in an extended lag phase and lower maximum growth rate in comparison with the untreated cells (p <= 0.05). In the presence of carvacrol, the lower inoculum size showed an increased growth rate and relatively longer lag phase compared to the higher inoculum size (p <= 0.05). The cells of L. innocua and L. monocytogenes had a greater extension of lag time, slower growth rate and higher percentage of injured cells when treated with carvacrol (p <= 0.05). Results also indicated that L. monocytogenes grows faster than L. innocua when treated with carvacrol, this scenery could compromise the use of L. innocua as a surrogate for L. monocytogenes serovar 4b for this antimicrobial substance. Finally, it was shown that good growth control of Listeria was achieved with 0.175 mu L/mL of carvacrol. (C) 2013 Elsevier Ltd. All rights reserved.

Most perishable food products are stored at low temperature in order to extend their shelf-life. However, this step does not eliminate undesirable microorganisms from these products. Alternative preservation techniques such as natural antimicrobial agents are being used or investigated for their application to food products. The aim was to evaluate the antimicrobial capacity of carvacrol on growth kinetic of Listeria innocua (CECT 910T). The bacterial growth rates were obtained from viable cell counts on Tryptone Soya Agar supplemented with 0.6% yeast extract (TSA-YE).The tested concentrations of carvacrol ranged from 0.100 to 0.175 µL/mL. Control samples of bacterial growth were evaluated on the absence of carvacrol. Experimental data were fitted to the modified Gompertz equation. The kinetic parameters of bacterial growth were characterized based on the time needed to environment adaptation (λ) and on the maximum specific growth rate (µmax). Studies carried out using 10 6 CFU/mL inoculum size of Listeria innocua shown that λ and µmax were influenced by the concentration of carvacrol as antimicrobial agent (p ≤ 0.05). As the concentration of car vacrol increased from 0.100 µL/mL to 0.175 µL/mL an increment of λ of 2.752 hours and a decrease of µmax of 0.178 log/h were observed (p0.05). In conclusion, it was verified that the carvacrol showed an inhibitory effect on the kinetic parameters of Listeria innocua growth therefore it can be a natural agent to extend shelf life of foods products.

A stochastic exposure assessment model was developed to predict the final load (Nf, CFU/mL) of Bacillus cereus cells after being treated by High Pressure Processing (HPP) (100, 200, 300 MPa) and stored (10 degrees C, 15 days), in a milk-egg-cocoa (12% rich in polyphenols) mixture beverage. Results indicated that beverage supplemented with cocoa powder had final B. cereus concentration level of 6 CFU/mL at 95% probability, being below the infectious dose (10(4)-10(5) CFU per mL) (Granum & Baird-Parker, 2000). The most important factors affecting the final load of B. cereus cells in this beverage were ranged as follows: cocoa supplementation > HPP treatment > initial load (Log N-0, CFU/mL) > and storage time (t(STORAGE), days). Those results show one more the usefulness of Monte Carlo simulation in performing exposure assessment studies focused on safety management at an industrial level. (C) 2012 Elsevier Ltd. All rights reserved.

Brazilian agribusiness became increasingly competitive on the global agribusiness stage primarily in the animal production. In the first quarter of 2011 were slaughtered 8.160 million of pigs and 1.306 billion of chickens. To ensure the productivity and competitiveness of the sector, the use of drugs as growth promoters is a common practice. However, the use of substances as antimicrobial growth promoters has been discussed and is subject to a series of rules because the literature has been reporting the presence of bacteria resistant. The concern about the growth of bacterial resistance to antibiotics has stimulated the search for alternatives that will replace these substances as growth promoters. The aim of this study was to evaluate the antibiotic sensibility of Listeria innocua (CECT 910) and Listeria monocytogenes (CECT 4032) in the presence of natural antimicrobial agents. The DMSO was used as dilution agent for obtaining the levels of 0.100 and 0.175 μL/mL for carvacrol and levels of 0.150 and 0.250 μL/mL for citral. Assessing the strains of L. monocytogenes and L. innocua, it was verified that the sensibility to erythromycin was of the 0.250 μg/mL. There was reduction of the minimal inibitory concentration (MIC) of erythromycin in the presence of antimicrobials carvacrol or citral in cultures of L. innocua and L. monocytogenes to 0.094-0.125 μg/mL. In this study the MIC of bacitracin in cultures of L. innocua and L. monocytogenes was of 32 μg/mL. However, there was reduction of MIC in the presence of antimicrobials carvacrol or citral. The MIC of colistin in cultures of L. innocua and L. monocytogenes was reduced in the presence of antimicrobial carvacrol or of citral from 96-128 μg/mL to 4 μg/mL. The results obtained in this study showed that the combined use of antibiotics with natural antimicrobial resulted in a synergistic effect demonstrated by the reduction of the MIC in cultured of L. monocytogenes and L. innocua.

With a view to extending the shelf-life and enhancing the safety of liquid whole egg/skim milk (LWE-SM) mixed beverages, a study was conducted with Bacillus cereus vegetative cells inoculated in skim milk (SM) and LWE-SM beverages, with or without antimicrobial cocoa powder. The beverages were treated with Pulsed Electric Field (PEF) technology and then stored at 5 C for 15 days. The kinetic results were modeled with the Bigelow model. Weibull distribution function, modified Gompertz equation, and Log-logistic models.Maximum inactivation registered a reduction of around 3 log cycles at 40 kV/cm, 360 mu s, 20 degrees C in both the SM and LWE-SM beverages. By contrast, in the beverages supplemented with the aforementioned antimicrobial compound, higher inactivation levels were obtained under the same treatment conditions, reaching a 3.30 log,a cycle reduction.The model affording the best fit for all four beverages was the four-parameter Log-logistic model. After 15 days of storage, the antimicrobial compound lowered Bacillus cereus survival rates in the samples supplemented with CocoanOX 12% by a 4 log cycle reduction, as compared to the untreated samples without CocoanOX 12%. This could indicate that the PEF-antimicrobial combination has a synergistic effect on the bacterial cells under study, increasing their sensitivity to subsequent refrigerated storage. (C) 2009 Elsevier B.V. All rights reserved.