Resistance of Enterobacter sakazakii to pulsed electric fields

Arroyo, Cristina; Cebrián, Guillermo; Pagán, Rafael; Condón, S.

doi:10.1016/j.ifset.2009.11.002

Cited by 38 publications

(22 citation statements)

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“…sakazakii has been scarcely studied (Pina‐Pérez et al. 2007, 2009; Arroyo et al. 2010), showing a remarkable influence of some environmental factors on its PEF resistance.…”

Section: Introductionmentioning

confidence: 99%

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Pulsed electric fields cause sublethal injuries in the outer membrane of Enterobacter sakazakii facilitating the antimicrobial activity of citral

Arroyo

Somolinos

Cebrián

et al. 2010

Letters in Applied Microbiology

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Aims: The objective was to evaluate the relation of sublethal injury in the outer membrane of Enterobacter sakazakii to the inactivating effect of the combination of pulsed electric fields (PEF) treatments and citral. Methods and Results: The occurrence of sublethal injury in the outer membrane was measured using selective recovery media containing bile salts. Loss of membrane integrity was measured by the increased uptake of the fluorescent dye propidium iodide (PI). PEF caused nonpermanent and permanent envelope permeabilization of Ent. sakazakii at pH 4·0. After PEF, most surviving cells showed transient cell permeabilization and sublethal injury in their outer membranes. The simultaneous application of a mild PEF treatment (100 pulses, 25 kV cm−1) and 200 μl l−1 of citral to cells suspended in pH 4·0 buffer at a final concentration of 107 cells per ml showed an outstanding synergistic lethal effect, causing the inactivation of more than two extra log10 cycles. Conclusions: Our results confirm that the detection of sublethal injury in the outer membrane after PEF may contribute to the identification of the treatment conditions under which PEF may act synergistically with hydrophobic compounds such as citral. Significance and Impact of the Study: Knowledge about the mechanism of microbial inactivation by PEF will aid the establishment of successful combined preservation treatments.

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“…sakazakii has been scarcely studied (Pina‐Pérez et al. 2007, 2009; Arroyo et al. 2010), showing a remarkable influence of some environmental factors on its PEF resistance.…”

Section: Introductionmentioning

confidence: 99%

“…It was the first time that sublethal injuries in the outer membrane of a Gram‐negative bacterium were found after PEF. These results (Arroyo et al. 2010) opened a chance to design combined processes, including the use of PEF and antimicrobial hydrophobic compounds for which the outer membrane acts as an impermeable barrier.…”

Section: Introductionmentioning

confidence: 99%

Pulsed electric fields cause sublethal injuries in the outer membrane of Enterobacter sakazakii facilitating the antimicrobial activity of citral

Arroyo

Somolinos

Cebrián

et al. 2010

Letters in Applied Microbiology

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“…Later, 1 ml aliquots were withganism applied is one of the factors classically studied, giving information specially useful for inoculation studies on laboratory and pilot plant scales, which provides the basic information for implementation in real scenarios. The growth phase effect on microbial inactivation has been identified also for other non-thermal technologies such as high pressure processing (Hayman et al 2007;Saucedo-Reyes et al 2009), supercritical carbon dioxide treatment (Ortuño et al 2012), pulsed electric fields (Arroyo et al 2010), and ultrasonic waves under pressure (Arroyo et al 2011). With PL, Gómez-López et al (2005) studied the inactivation of Listeria monocytogenes during the growth.…”

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confidence: 99%

Effects of shading and growth phase on the microbial inactivation by pulsed light

Cudemos¹,

Izquier²,

Medina-Martínez³

et al. 2013

Czech J. Food Sci.

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Cudemos E., Izquier A., Medina-Martínez M.S., Gómez-López V.M. (2013): Effects of shading and growth phase on the microbial inactivation by pulsed light. Czech J. Food Sci., 31: 189-193. Pulsed light is an emerging technology that kills microorganisms using pulses of an intense broad-spectrum light. This work aimed to determine the effect of population density and microbial growth phase on its microbicidal efficacy. To this, pseudomonas fluorescens cultures were grown, diluted to different population densities, flashed, plated, incubated, and enumerated, Also, cultures of p. fluorescens, Bacillus cereus, and saccharomyces cerevisiae were taken at different growth phases, diluted to the same population density, flashed, plated, incubated, and enumerated. Microbial inactivation was lower at high densities, probably as the consequence of the shading effect, and higher at the exponential phase. This study sets the background information useful for scientists and industrial implementation. The population density and growth phase must be taken into account in the planning experiments and comparing the literature. On the industrial scale, heavily contaminated solids are not suitable for pulsed light (PL) treatment; while liquids should receive several PL flashes under the flow conditions that assure that all microorganisms receive a PL treatment, that should be also designed in function of the growth phase of the microbial contaminant.Keywords: UV-C light; non-thermal methods; shading effect; decontamination; inactivation Pulsed light (PL) is a non-thermal emerging technology to decontaminate surfaces and transparent liquids by killing microorganisms using pulses of an intense broad-spectrum light where its UV-C part is the most lethal (Gómez-López et al. 2007).The shading effect is usually cited as a limiting factor of PL efficacy. It occurs when microorganisms are present one upon another, which causes that those at the top can be killed by PL but protect in turn the underlying microorganisms (Gómez-López et al. 2007). Its existence is claimed from the beginning of the use of PL as a germicidal method, however, just for specific microorganisms that readily absorb UV rays such as Aspergillus niger and not as a general limiting factor (Hiramoto 1984). Furthermore, the patent of Hiramoto (1984) also claimed that this phenomenon occurs with the conventional UV lamps and is overcome by the photothermal effect of PL. On the other side, Farrell et al. (2010) reported a population density effect in the inactivation curves of staphylococcus aureus and pseudomonas aeruginosa, where tailing was only observed at very high initial sizes.The susceptibility of microorganisms to inactivation by physical methods depends on several factors, which depend in turn on the specific method. The effect of the growth phase of the microor- 190Vol. 31, 2013, No. 2: 189-193 Czech J. Food Sci. PL equipment. PL processing was performed using a XeMaticA-1XL system (SteriBeam GmbH, Kehl, Germany), which had been described previously (I...

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“…Since the recognition of C. sakazakii as an important emerging food-borne pathogen, several research papers have focused on the characterization of the tolerance of C. sakazakii to relevant envi- ronmental stress conditions (1,2,3,4,11,16,21,50). However, most of these works focused on a single strain or a very limited number of C. sakazakii strains, and there is a lack of comprehensive studies addressing the heterogeneity in stress tolerance among natural isolates of C. sakazakii.…”

Section: Discussionmentioning

confidence: 99%

Polymorphisms in rpoS and Stress Tolerance Heterogeneity in Natural Isolates of Cronobacter sakazakii

Álvarez‐Ordóñez

Begley

Hill

2012

Appl Environ Microbiol

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ABSTRACTSignificant phenotypic diversity was observed when we examined the abilities of a number ofCronobacter sakazakiinatural isolates to cope with various sublethal stress conditions (acid, alkaline, osmotic, oxidative, or heat stress). Levels of catalase activity and use of acetate as a carbon source, phenotypes commonly used as indirect assays to predict RpoS function, revealed a high correlation between predicted RpoS activity and tolerance to acid, alkaline, osmotic, and oxidative treatments. TherpoSgenes were sequenced and analyzed for polymorphisms. Loss-of-function mutations were found in two strains;C. sakazakiiDPC 6523 and the genome-sequenced strainC. sakazakiiATCC BAA-894. The complementation of these strains with a functionalrpoSgene resulted in an increase in bacterial tolerance to acid, osmotic, and oxidative stresses. The pigmentation status of strains was also assessed, and a high variability in carotenoid content was observed, with a functionalrpoSgene being essential for the production of the characteristic yellow pigment. In conclusion, the evidence presented in this study demonstrates thatrpoSis a highly polymorphic gene inC. sakazakii, and it supports the importance of RpoS for the tolerance under stress conditions thatC. sakazakiimay encounter in the food chain and in the host during infection.

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Resistance of Enterobacter sakazakii to pulsed electric fields

Cited by 38 publications

References 50 publications

Pulsed electric fields cause sublethal injuries in the outer membrane of Enterobacter sakazakii facilitating the antimicrobial activity of citral

Pulsed electric fields cause sublethal injuries in the outer membrane of Enterobacter sakazakii facilitating the antimicrobial activity of citral

Effects of shading and growth phase on the microbial inactivation by pulsed light

Polymorphisms in rpoS and Stress Tolerance Heterogeneity in Natural Isolates of Cronobacter sakazakii

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