RESUMO
The influence of chemical diluents on the antimicrobial activity of plant essential oil (EO) vapors was evaluated. We first determined if vapors generated from 22 chemical diluents not containing EO had antimicrobial activities. Ethyl ether vapor retarded the growth of S. aureus. The minimal inhibitory concentrations (MICs) and the minimal lethal concentrations (MLCs) of cinnamon bark EO vapor, which was diluted in and generated from 21 diluents, against S. aureus and S. enterica were determined. Cinnamon bark EO vapor showed significantly (P ≤ 0.05) lower MICs against S. aureus when diluted in dimethyl sulfoxide (DMSO), ethanol, ethyl acetate, or jojoba oil, and against S. enterica when diluted in DMSO, ethanol, or jojoba oil, compared to those in other diluents. We compared antimicrobial activities of cinnamon bark EO vapor diluted in DMSO, ethanol, ethyl acetate, or jojoba oil against S. aureus and S. enterica on beef jerky as a food model. Antimicrobial activity was significantly (P ≤ 0.05) higher when vaporized from DMSO. These results indicate that antimicrobial activity of cinnamon bark EO vapor may vary significantly (P ≤ 0.05) depending on the type of diluent from which it is vaporized. These observations provide basic information when developing food and food-contact surface decontamination strategies using EO vapors.
Assuntos
Anti-Infecciosos , Óleos Voláteis , Salmonella enterica , Animais , Bovinos , Staphylococcus aureus , Cinnamomum zeylanicum , Dimetil Sulfóxido , Casca de Planta , Óleos Voláteis/farmacologia , Óleos de Plantas/farmacologia , Gases , Anti-Infecciosos/farmacologia , Etanol , Testes de Sensibilidade MicrobianaRESUMO
AIM: This study was done to develop a seed decontamination treatment for organic seeds against plant pathogens (Acidovorax citrulli and Xanthomonas campestris) using essential oil (EO) vapours without affecting the seeds' germination rate. METHODS AND RESULTS: By using a diffusion assay and determining minimum inhibitory and lethal concentrations, we screened two EO vapours which were most inhibitory to A. citrulli (cinnamon bark and garlic EO vapours) and X. campestris (onion and garlic EO vapours). After 48 h of exposure to EO vapours at 25°C and 43% or 85% relative humidity (RH), no significant decrease (p > 0.05) in germination rates was observed compared with those of control seeds. It was observed that EO vapour treatment at 25°C and 43% or 85% RH for 48 h caused significant population reductions (p ≤ 0.05) (ca. 0.3-2.6 log colony forming unit/g) compared to those of untreated seeds. CONCLUSION: Applications of EO vapours showed significant (p ≤ 0.05) antimicrobial effects against A. citrulli and X. campestris on both laboratory mediums and plant seeds without decreasing the germination rate of seeds. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides useful information for the development of natural seed sterilization treatments using EO vapours.
Assuntos
Anti-Infecciosos , Brassicaceae , Cucurbitaceae , Óleos Voláteis , Solanaceae , Xanthomonas campestris , Comamonadaceae , Óleos Voláteis/farmacologia , Óleos de Plantas/farmacologia , SementesRESUMO
AIM: This study was done to determine the effects of temperature, pH and sodium chloride (NaCl) on antimicrobial activity of magnesium oxide (MgO) nanoparticles (NPs) against E. coli O157:H7. METHODS AND RESULTS: Culture conditions were established by varying the pH (5.0, 7.2 and 9.0), NaCl concentration (0.5, 2.0, 3.5 and 5.0%, w/v), and incubation temperatures (4, 12, 22 and 37°C). At each condition, the antimicrobial activities of MgO-NPs (0, 1, 2 and 4 mg/ml) against E. coli O157:H7 were measured. Four-way analysis of variance indicated interactions among all factors had a significant effect (p ≤ 0.05) on the antimicrobial activity of MgO-NPs. The concentration of MgO-NPs necessary to cause a 5-log reduction of E. coli O157:H7 under the most inhibitory conditions (37°C, pH 9.0, and 5.0% NaCl) was 0.50 mg/ml of MgO-NPs. CONCLUSION: The antimicrobial activity of the MgO-NPs increased significantly (p ≤ 0.05) with increased temperature, pH and NaCl concentration in TSB. SIGNIFICANCE AND IMPACT OF THE STUDY: The influence of intrinsic and extrinsic factors on antimicrobial activity of MgO-NPs we found will contribute to the development of microbial decontamination strategies using MgO in the food industry.
Assuntos
Anti-Infecciosos , Escherichia coli O157 , Nanopartículas , Anti-Infecciosos/farmacologia , Contagem de Colônia Microbiana , Microbiologia de Alimentos , Concentração de Íons de Hidrogênio , Óxido de Magnésio/farmacologia , Cloreto de Sódio/farmacologia , TemperaturaRESUMO
This study was done to develop a method to inactivate Escherichia coli O157:H7 on radish and cabbage seeds using simultaneous treatments with gaseous chlorine dioxide (ClO2) and heat at high relative humidity (RH) without decreasing seeds' viability. Gaseous ClO2 was spontaneously vaporized from a solution containing hydrochloric acid (HCl, 1 N) and sodium chlorite (NaClO2, 100,000 ppm). Using a sealed container (1.8 L), an equation (y = 5687×, R2 = 0.9948) based on the amount of gaseous ClO2 generated from HCl-NaClO2 solution at 60 °C and 85% RH was developed. When radish or cabbage seeds were exposed to gaseous ClO2 at concentrations up to 3,000 ppm for 120 min, germination rates did not significantly decrease (P > 0.05). When seeds inoculated with E. coli O157:H7 were treated with 2,000 or 3,000 ppm of gaseous ClO2 in an atmosphere with 85% RH at 60 °C, populations (6.8-6.9 log CFU/g) on both types of seeds were decreased to below the detection limit for enrichment (-0.5 log CFU/g) within 90 min. This study provides useful information for developing a decontamination method to control E. coli O157:H7 and perhaps other foodborne pathogens on plant seeds by simultaneous treatment with gaseous ClO2 and heat at high RH.
Assuntos
Brassica/crescimento & desenvolvimento , Compostos Clorados/farmacologia , Descontaminação/métodos , Desinfetantes/farmacologia , Escherichia coli O157/efeitos dos fármacos , Óxidos/farmacologia , Raphanus/crescimento & desenvolvimento , Sementes/microbiologia , Brassica/microbiologia , Cloro/farmacologia , Escherichia coli O157/crescimento & desenvolvimento , Germinação/efeitos dos fármacos , Temperatura Alta , Umidade , Viabilidade Microbiana/efeitos dos fármacos , Raphanus/microbiologia , Sementes/química , Sementes/crescimento & desenvolvimentoRESUMO
We investigated combinations of gaseous essential oils (EO gases) for their synergistic inhibitory activities against Listeria monocytogenes on a laboratory medium and radish sprouts. The minimum inhibitory concentrations and minimum lethal concentrations of oregano, thyme thymol, and cinnamon bark EO gases against L. monocytogenes were 0.0781⯵L/mL on nutrient agar supplemented with glucose and bromocresol purple (NGBA). A checkerboard assay showed that combinations of oregano and thyme thymol EO gases and of oregano and cinnamon bark EO gases exert the strongest synergistic antilisterial activity (fractional inhibitory concentration index [FICI]â¯=â¯0.3750). A combination of thyme thymol and cinnamon bark EO gases also had a synergistic effect (FICIâ¯=â¯0.5000) on L. monocytogenes on NGBA. Combinations of oregano and thyme thymol EO gases were tested for synergistic antimicrobial activity against L. monocytogenes on radish sprouts. A combination of these gases, each at 0.313⯵L/mL, caused a significant (Pâ¯≤â¯0.05) reduction in the number of L. monocytogenes on radish sprouts compared with reductions caused by treatment with oregano or thyme thymol EO gas alone at the same concentration. Our findings provide information that will be useful when developing antimicrobial applications using EO gases to control L. monocytogenes in the food industry.
Assuntos
Antibacterianos/farmacologia , Listeria monocytogenes/efeitos dos fármacos , Óleos Voláteis/farmacologia , Origanum/química , Raphanus/microbiologia , Timol/farmacologia , Thymus (Planta)/química , Antibacterianos/química , Cinnamomum zeylanicum/química , Meios de Cultura/química , Meios de Cultura/metabolismo , Sinergismo Farmacológico , Gases/farmacologia , Listeria monocytogenes/crescimento & desenvolvimento , Testes de Sensibilidade Microbiana , Óleos Voláteis/química , Óleos de Plantas/química , Óleos de Plantas/farmacologia , Raphanus/crescimento & desenvolvimento , Timol/químicaRESUMO
The common use of gloves in retail practices represents a potential route for cross contamination of foodborne pathogens in fresh-cut produce. Using fresh-cut cantaloupe as a food model, we investigated factors that may influence glove-mediated cross contamination by Listeria monocytogenes and developed mathematical models to illustrate the patterns of transfer during fresh-cutting practices. Contact time (2, 5, 10 s), contact pressure (0.05, 0.18, 0.37 psi), and glove type (nitrile, polyvinyl chloride, polyethylene) did not have a significant effect on transfer of L. monocytogenes from cantaloupe rind to flesh, or from flesh to flesh. However, glove type appeared to affect L. monocytogenes transfer from the stem scar tissue to cantaloupe flesh (P = 0.0371). Transfer from rind pieces that had been washed with water was significantly higher than transfer from pieces that had not been washed (P = 0.0006). Predictive modeling and experimental validation suggested that transfer of L. monocytogenes on cantaloupe flesh persists over 85 pieces through consecutive contacts with a gloved hand. Findings of the study provide new scientific data to aid researchers, retailers, and caterers in safety risk assessments of fresh-cut practices used to prepare cantaloupes and other produce items.
Assuntos
Cucumis melo/microbiologia , Contaminação de Alimentos , Microbiologia de Alimentos , Frutas/microbiologia , Luvas Protetoras/microbiologia , Listeria monocytogenes/isolamento & purificação , Contagem de Colônia Microbiana , Manipulação de Alimentos , Listeria monocytogenes/crescimento & desenvolvimento , Modelos Teóricos , Temperatura , ÁguaRESUMO
This study investigated the antimicrobial activities of organic acid vapors against a phytopathogen (Acidovorax citrulli) and foodborne pathogens (Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes) on the surface of Cucurbitaceae seeds. Germination percentages of cucumber, honeydew melon and watermelon seeds treated with acetic and propionic acid vapors (100 mg/L) at 50 °C and 43% or 85% relative humidity (RH) for up to 2 h did not significantly (P > 0.05) decrease. Treatment with formic acid significantly (P ≤ 0.05) decreased the germination percentage. The antimicrobial activities of acetic and propionic acid vapors (100 mg/L; 50 °C; 43% or 85% RH) were determined. A. citrulli was inactivated within 1 h on cucumber and watermelon seeds, regardless of type of organic acid or RH. The phytopathogen was reduced to levels below the detection limit (-0.5 log CFU/g) for enrichment on honeydew melon seeds treated with acetic acid vapor. S. enterica and L. monocytogenes were inactivated within 2 h at 85% RH on honeydew melon and watermelon seeds treated with acetic acid and propionic acid vapors. E. coli O157: H7 was inactivated by treatment with acetic acid vapor at 85% RH. This study provides useful information for developing a method to decontaminate Curcurbitaceae seeds using organic acid vapors as lethal agents.
Assuntos
Ácidos/farmacologia , Antibacterianos/farmacologia , Cucurbitaceae/microbiologia , Escherichia coli O157/efeitos dos fármacos , Listeria monocytogenes/efeitos dos fármacos , Salmonella enterica/efeitos dos fármacos , Ácido Acético/química , Ácido Acético/farmacologia , Ácidos/química , Antibacterianos/química , Comamonadaceae/efeitos dos fármacos , Comamonadaceae/crescimento & desenvolvimento , Cucurbitaceae/crescimento & desenvolvimento , Escherichia coli O157/crescimento & desenvolvimento , Formiatos/química , Formiatos/farmacologia , Germinação , Listeria monocytogenes/crescimento & desenvolvimento , Propionatos/química , Propionatos/farmacologia , Salmonella enterica/crescimento & desenvolvimento , Sementes/crescimento & desenvolvimento , Sementes/microbiologiaRESUMO
This study was done to identify combinations of essential oils (EOs) that elicit synergistic antimicrobial effects against Leuconostoc citreum, a spoilage bacterium in vegetable and fruit juices. Twenty-four EOs were tested for antimicrobial activity against L. citreum using an agar well diffusion assay. Ten EOs showed relatively strong antimicrobial activity. Among those, cinnamon bark, oregano, and thyme thymol EOs showed the strongest activity (minimal inhibitory concentration = 1.25 µL/mL). It was confirmed that a combination of oregano and thyme thymol EOs had a synergistic antimicrobial activity (fractional inhibitory concentration index = 0.3750) using a checkerboard assay. This combination also had a synergistic antimicrobial activity against L. citreum in tomato juice. An initial population of L. citreum in tomato juice (5.3 log CFU/mL) increased to ≥ 8.6 log CFU/mL within 48 h at 15 °C and 24 h at 25 °C. Populations reached 6.8-7.2 log CFU/mL in tomato juice containing either 0.156 mL/mL oregano or thyme thymol. However, in the presence of both EOs (0.156 µL/mL in total), populations of L. citreum were significantly lower (5.7-6.5 log CFU/mL) (P ≤ 0.05). Findings will be useful when developing non-thermal food preservation technologies to increase the shelf-life of juices and other foods not containing synthetic preservatives.
Assuntos
Anti-Infecciosos/farmacologia , Sucos de Frutas e Vegetais/microbiologia , Leuconostoc/efeitos dos fármacos , Óleos Voláteis/farmacologia , Origanum/química , Óleos de Plantas/farmacologia , Timol/farmacologia , Cinnamomum zeylanicum/química , Meios de Cultura/química , Meios de Cultura/farmacologia , Sinergismo Farmacológico , Microbiologia de Alimentos/métodos , Conservação de Alimentos/métodos , Solanum lycopersicum/microbiologia , Testes de Sensibilidade Microbiana , Thymus (Planta)/químicaRESUMO
Of the 1648 microbial isolates from 133 soil samples collected from 30 diverse locations in the Republic of Korea, two isolates exhibited strong antilisterial activity and ability to grow to high populations (>8.0 log CFU/ml) in Bennett's broth. Isolates were identified as Streptomyces lactacystinicus (strain Samnamu 5-15) and Streptomyces purpureus (strain Chamnamu-sup 4-15). Both isolates formed biofilms on the surface of stainless steel coupons (SSCs) immersed in Bennett's broth within 24â¯hâ¯at 25⯰C. Cells retained antilisterial activity after biofilm formation and showed significantly (Pâ¯≤â¯0.05) enhanced resistance against dry conditions (43% relative humidity [RH]) compared to the cells not in biofilm. An initial population (ca. 3.2 log CFU/cm2) of Listeria monocytogenes inoculated on SSCs lacking Streptomyces biofilm decreased to 1.4 log CFU/cm2 within 48â¯hâ¯at 25⯰C and 43% RH. In contrast, L. monocytogenes (3.3 log CFU/cm2) inoculated on SSCs containing Streptomyces biofilm decreased to populations below the theoretical detection limit (0.5 log CFU/cm2) within 24â¯h. The results indicate that biofilms formed by the Streptomyces spp. inhibitory to L. monocytogenes showed enhanced resistance to desiccation condition (43% RH) and effectively inhibited the growth of L. monocytogenes on the surfaces of SSCs. Antilisterial biofilms developed in this study may be applicable on desiccated environmental surfaces in food related environments such as food storage, handling, and processing facilities to enhance the microbiological safety of foods.
Assuntos
Antibiose , Biofilmes , Listeria monocytogenes/crescimento & desenvolvimento , Aço Inoxidável/análise , Streptomyces/fisiologia , Contagem de Colônia Microbiana , Dessecação , Manipulação de Alimentos , Microbiologia de Alimentos , República da Coreia , Microbiologia do Solo , Streptomyces/crescimento & desenvolvimento , Streptomyces/isolamento & purificaçãoRESUMO
BACKGROUND: Acidovorax citrulli is a plant pathogen causing bacterial fruit blotch in Cucurbitaceae family. Applying high concentration of disinfectants to seeds containing plant pathogen may substantially decrease the germination rate of seeds. Therefore, it is necessary to develop a hurdle technology which can inactivate plant pathogens without decreasing seed viability. This study was conducted to develop a decontamination method to inactivate the plant pathogen Acidovorax citrulli on Cucurbitaceae seeds by sequential treatments with aqueous chlorine dioxide (ClO2 ), drying, and dry heat. RESULTS: The maximum ClO2 concentration that did not lower germination rates of cucumber, honeydew melon, and watermelon seeds was ca. 100 µg mL-1 of ClO2 for 5 min. Optimal incubation conditions for drying seeds that had been treated with aqueous ClO2 were determined as 25 °C and 43% relative humidity (RH) for 48 h. The maximum dry-heat temperature that did not reduce germination rates of seeds, which had been treated with ClO2 and dried at 25 °C, was 60 °C at 43% RH for 24 h. When seeds containing A. citrulli (6.4-7.0 log CFU g-1 ) were treated with aqueous ClO2 (50 µg mL-1 , 5 min), dried (25 °C, 43% RH, 24 h), and dry heated (60 °C, 43% RH, 24 h), the pathogen was inactivated to below the detection limit from all three seed types (<-0.5 log CFU g-1 ). CONCLUSION: The decontamination conditions to inactivate A. citrullii from Cucurbitaceae seeds without decreasing the seed viability were determined (sequential treatment with ClO2 [50 µg mL-1 , 5 min], dried [25 °C, 43% RH, 24 h], and dry heated [60 °C, 43% RH, 24 h]). The results of this study may also be applicable to other plant pathogens on other types of seeds. © 2019 Society of Chemical Industry.
Assuntos
Comamonadaceae/efeitos dos fármacos , Cucurbitaceae/microbiologia , Descontaminação/métodos , Sementes/crescimento & desenvolvimento , Compostos Clorados/farmacologia , Comamonadaceae/crescimento & desenvolvimento , Cucurbitaceae/crescimento & desenvolvimento , Descontaminação/instrumentação , Dessecação , Desinfetantes/farmacologia , Germinação , Óxidos/farmacologia , Doenças das Plantas/microbiologia , Doenças das Plantas/prevenção & controle , Sementes/microbiologiaRESUMO
Non-pathogenic bacterial biofilms were developed on the surface of stainless steel possessing desiccation tolerance and antimicrobial activity against Salmonella enterica. Three bacteria exhibiting strong antimicrobial activities against S. enterica were isolated from various soils, foods, and food-contact surfaces. Isolates were identified as Pseudomonas extremorientalis (strain Lettuce-28), Paenibacillus peoriae (strain Lettuce-7), and Streptomyces cirratus (strain Geumsan-207). These bacteria grew rapidly and formed biofilms within 24 h on the surface of stainless steel coupons (SSCs) immersed in laboratory media (tryptic soy broth or Bennet's broth) at 25 °C. Cells in biofilms had enhanced tolerance to desiccation (exposure to 43% atmospheric relative humidity [RH]) and retained antimicrobial activity against S. enterica. Populations of S. enterica deposited on SSCs containing biofilm formed by Ps. extremorientalis strain Lettuce-28, for example, decreased by > 2.5 log CFU/coupon within 24 h at 25 °C and 43% RH, while the number of cells inoculated on SSCs lacking biofilm decreased by 1.5 log CFU/coupon. Antimicrobial activities of the three antagonistic bacteria against S. enterica persisted in desiccated biofilms. This study provides insights to developing strategies to inactivate Salmonella and perhaps other foodborne pathogens on abiotic surfaces using non-pathogenic antagonistic bacteria.
Assuntos
Biofilmes , Pseudomonas/fisiologia , Salmonella enterica/fisiologia , Aço Inoxidável/análise , Antibiose , Microbiologia de Alimentos , Pseudomonas/crescimento & desenvolvimento , Pseudomonas/isolamento & purificação , Salmonella enterica/crescimento & desenvolvimento , Microbiologia do SoloRESUMO
Chili pepper (Capsicum annuum L.) powder and other powdered spices containing chili peppers are occasionally contaminated with foodborne pathogens. We applied chlorine dioxide (ClO2) gas treatment to chili peppers prior to drying to inactivate Salmonella Typhimurium. Chili peppers inoculated with S. Typhimurium were exposed to ClO2 gas generated from 0.77â¯mL of aqueous ClO2 for 6â¯hâ¯at 25⯰C and 100% relative humidity, followed by air drying at 55⯰C for up to 24â¯h. Populations of S. Typhimurium and total aerobic bacteria (TAB) on peppers, chromaticity values, and moisture content were determined after various treatment times. S. Typhimurium (ca. 5.6 log cfu/g) was reduced to <0.7 log cfu/g of peppers treated with ClO2 gas for 0.5â¯hâ¯at 25⯰C, but was detected by enrichment (>1â¯cfu/10.8â¯g) after treatment for 4â¯h. The pathogen was not detected after treatment with ClO2 gas for 6â¯h. S. Typhimurium did not decrease significantly (Pâ¯>â¯0.05) on peppers exposed to air at 25⯰C for 6â¯h, but rapidly decreased to 1.6 log cfu/g after subsequent drying for 6â¯hâ¯at 55⯰C. The initial number of TAB (ca. 6.5 log cfu/g) decreased to 1.4 log cfu/g after treatment with ClO2 gas for 0.5â¯h and was less than the detection limit (0.7 log cfu/g) after 2â¯h. TAB counts were not reduced by treating peppers with air for 6â¯h, but decreased to <0.7 log cfu/g after subsequent drying for 24â¯hâ¯at 55⯰C. The lightness (L value) of treated and untreated chili peppers did not change during drying, but redness (a value) and yellowness (b value) decreased. Results showed that treatment of chili peppers containing S. Typhimurium (5.6 log cfu/g) with ClO2 gas for 6â¯h prior to drying at 55⯰C reduced the population toâ¯<â¯1â¯cfu/10.8â¯g.
Assuntos
Capsicum/microbiologia , Compostos Clorados/farmacologia , Dessecação , Viabilidade Microbiana/efeitos dos fármacos , Óxidos/farmacologia , Salmonella typhimurium/efeitos dos fármacos , Contagem de Colônia Microbiana , Cor , Microbiologia de Alimentos , Gases/farmacologia , Salmonella typhimurium/patogenicidade , Salmonella typhimurium/fisiologiaRESUMO
The aim of this study was to investigate the lethal effects of simultaneous treatments with gaseous chlorine dioxide (ClO2) and mild wet heat (55 °C at 100% relative humidity [RH]) on Salmonella enterica in chicken feces on the surface of eggshells. Gaseous ClO2 production decreased significantly (P ≤ 0.05) as the RH (23, 43, 68, 85, and 100%) at 25 °C was increased. The lethality of gaseous ClO2 against S. enterica in feces on eggshells increased significantly (P ≤ 0.05) as RH increased. For example, when treated with gaseous ClO2 at 85 and 100% RH at 25 °C, S. enterica (5.9 log CFU/egg) was inactivated within 4 h. In contrast, at 23, 43, and 68% RH, the pathogen remained at 5.1, 5.0, and 2.8 log CFU/egg, respectively, after 6 h. Finally, when eggshells surface-contaminated with S. enterica (5.8 log CFU/egg) were treated with gaseous ClO2 (peak concentration of ClO2: 185.6 ppm) at 100% RH and 55 °C, inactivation occurred within 1 h. These results indicate that treatment of surface-contaminated shell eggs with gaseous ClO2 at elevated RH and temperature is effective in inactivating S. enterica. These observations will be useful when developing an effective sanitation program to enhance the microbiological safety of shell eggs.
Assuntos
Compostos Clorados/farmacologia , Desinfetantes/farmacologia , Casca de Ovo/microbiologia , Fezes/microbiologia , Óxidos/farmacologia , Salmonella enterica/efeitos dos fármacos , Animais , Galinhas , Contagem de Colônia Microbiana , Casca de Ovo/efeitos dos fármacos , Microbiologia de Alimentos , Gases , Temperatura Alta , Umidade , Salmonella enterica/crescimento & desenvolvimentoRESUMO
We compared the microbiological quality of chicken eggshells obtained from a traditional wholesale market and a modern supermarket. We also determined the survival and growth characteristics of naturally occurring mesophilic aerobic bacteria (MAB) and artificially inoculated Salmonella enterica on eggshells under various environmental conditions (presence of chicken feces, temperature [4, 12, or 25 °C], and relative humidity [RH; 43 or 85%]). The populations of MAB, coliforms, and molds and yeasts on eggshells purchased from a traditional wholesale market were significantly (P ≤ 0.05) higher than those from a modern supermarket. In the second study, when we stored uninoculated eggs under various storage conditions, the population of MAB on eggshells (4.7-4.9 log CFU/egg) remained constant for 21 days, regardless of storage conditions. However, when eggshells were inoculated with S. enterica and stored under the same conditions, populations of the pathogen decreased significantly (P ≤ 0.05) under all tested conditions. Survival of S. enterica increased significantly (P ≤ 0.05) in the presence of feces, at low temperatures, and at low RH. These observations will be of value when predicting the behavior of microorganisms on eggshells and selecting storage conditions that reduce the populations of S. enterica on eggshells during distribution.
Assuntos
Bactérias Aeróbias/crescimento & desenvolvimento , Ovos/microbiologia , Fezes/microbiologia , Armazenamento de Alimentos/métodos , Salmonella enterica/crescimento & desenvolvimento , Animais , Bactérias Aeróbias/isolamento & purificação , Galinhas , Temperatura Baixa , Contagem de Colônia Microbiana , Qualidade de Produtos para o Consumidor , Casca de Ovo/microbiologia , Contaminação de Alimentos/análise , Armazenamento de Alimentos/instrumentação , Umidade , Salmonella enterica/isolamento & purificaçãoRESUMO
We investigated the survival and growth patterns of Aspergillus flavus and Fusarium graminearum, as well as mycotoxin production, on Korean rice as affected by the degree of milling (rough, brown, and white rice) and storage conditions (21 °C/85% relative humidity [RH], 21 °C/97% RH, and 30 °C/85% RH). When rice was stored at 21 °C/85% RH, the population of A. flavus remained constant and aflatoxin was not produced, regardless of the degree of milling. At 21 °C/97% RH and 30 °C/85% RH, the populations of A. flavus increased significantly (P ≤ 0.05) and aflatoxins were produced. The highest population of A. flavus and highest amount of aflatoxin B1 were observed on brown rice stored at 21 °C/97% RH. For F. graminearum, when stored at 85% RH, the populations were reduced to less than a detectable level (5 CFU/g of rice) within 120 days and no deoxynivalenol (DON) was produced, regardless of the degree of milling and storage temperature. However, at 21 °C/97% RH, the population of F. graminearum increased significantly (P ≤ 0.05) and DON was produced on all types of rice. Findings from this study provide insights concerning storage conditions necessary to prevent growth and mycotoxin production by A. flavus and F. graminearum on Korean rice with different degrees of milling.
Assuntos
Aspergillus flavus/crescimento & desenvolvimento , Contaminação de Alimentos/análise , Armazenamento de Alimentos/métodos , Fusarium/crescimento & desenvolvimento , Oryza/microbiologia , Esporos Fúngicos/crescimento & desenvolvimento , Aflatoxinas/análise , Aflatoxinas/biossíntese , Aspergillus flavus/metabolismo , Manipulação de Alimentos , Fusarium/metabolismo , Umidade , Oryza/química , Oryza/classificação , Tamanho da Partícula , TemperaturaRESUMO
We determined the prevalence of and toxin production by Bacillus cereus and Bacillus thuringiensis in Korean rice as affected by production area and degree of milling. Rough rice was collected from 64 farms in 22 agricultural areas and polished to produce brown and white rice. In total, rice samples were broadly contaminated with B. cereus spores, with no effect of production area. The prevalence and counts of B. cereus spores declined as milling progressed. Frequencies of hemolysin BL (HBL) production by isolates were significantly (P ≤ 0.01) reduced as milling progressed. This pattern corresponded with the presence of genes encoding the diarrheal enterotoxins. The frequency of B. cereus isolates positive for hblC, hblD, or nheB genes decreased as milling progressed. Because most B. cereus isolates from rice samples contained six enterotoxin genes, we concluded that B. cereus in rice produced in Korea is predominantly of the diarrheagenic type. The prevalence of B. thuringiensis in rice was significantly lower than that of B. cereus and not correlated with production area. All B. thuringiensis isolates were of the diarrheagenic type. This study provides information useful for predicting safety risks associated with B. cereus and B. thuringiensis in rough and processed Korean rice.
Assuntos
Bacillus cereus/isolamento & purificação , Bacillus thuringiensis/isolamento & purificação , Enterotoxinas/metabolismo , Contaminação de Alimentos/análise , Oryza/microbiologia , Esporos Bacterianos/crescimento & desenvolvimento , Bacillus cereus/genética , Bacillus cereus/crescimento & desenvolvimento , Bacillus cereus/metabolismo , Bacillus thuringiensis/genética , Bacillus thuringiensis/crescimento & desenvolvimento , Bacillus thuringiensis/metabolismo , Qualidade de Produtos para o Consumidor , Contaminação de Alimentos/estatística & dados numéricos , Manipulação de Alimentos , República da Coreia , Esporos Bacterianos/genética , Esporos Bacterianos/isolamento & purificação , Esporos Bacterianos/metabolismoRESUMO
We studied the survival and growth patterns of Bacillus cereus, mesophilic aerobic bacteria (MAB), and molds and yeasts (MY) on rough and milled brown and white Korean rice stored at 12 and 21 °C and 43, 68, and 85% relative humidity (RH) for up to 24 wk. The initial populations of MAB present on rough rice, brown rice, and white rice were 7.7, 5.7, and 3.3 log CFU/g, respectively, and remained constant or decreased (P ≤ 0.05) by 0.7-1.8 log CFU/g during storage. The initial populations of B. cereus on the three types of laboratory-inoculated rice were 3.1-3.8 log CFU/g and remained constant (P > 0.05) during storage, regardless of degree of milling, storage temperature, and RH. The initial populations of MY on rough rice, brown rice, and white rice were 6.2, 4.2, and 2.1 log CFU/g, respectively. At 12 °C and 85% RH, the MY increased significantly (P ≤ 0.05) only on brown rice; however, at 21 °C and 85% RH, MY increased (P ≤ 0.05) on all types of rice during storage. These observations will be useful when assessing conditions affecting survival of B. cereus and determining environmental conditions necessary to prevent growth of potentially mycotoxigenic molds on various types of milled rice during storage.
Assuntos
Bacillus cereus/crescimento & desenvolvimento , Bactérias/crescimento & desenvolvimento , Fungos/crescimento & desenvolvimento , Microbiota , Oryza/microbiologia , Bacillus cereus/isolamento & purificação , Armazenamento de Alimentos , Umidade , TemperaturaRESUMO
BACKGROUND: The survival and distribution of enteric pathogens in soil and lettuce systems were investigated in response to several practices (soil amendment supplementation and reduced watering) that could be applied by home gardeners. RESULTS: Leaf lettuce was grown in manure compost/top soil (0:5, 1:5 or 2:5 w/w) mixtures. Escherichia coli O157:H7 or Salmonella was applied at a low or high dose (10(3) or 10(6) colony-forming units (CFU) mL(-1) ) to the soil of seedlings and mid-age plants. Supplementation of top soil with compost did not affect pathogen survival in the soil or on root surfaces, suggesting that nutrients were not a limiting factor. Salmonella populations on root surfaces were 0.7-0.8 log CFU g(-1) lower for mid-age plants compared with seedlings. E. coli O157:H7 populations on root surfaces were 0.8 log CFU g(-1) lower for mid-age plants receiving 40 mL of water compared with plants receiving 75 mL of water on alternate days. Preharvest internalization of E. coli O157:H7 and Salmonella into lettuce roots was not observed at any time. CONCLUSION: Based on the environmental conditions and high pathogen populations in soil used in this study, internalization of Salmonella or E. coli O157:H7 into lettuce roots did not occur under practices that could be encountered by inexperienced home gardeners.
Assuntos
Escherichia coli O157 , Microbiologia de Alimentos , Jardinagem , Lactuca/microbiologia , Raízes de Plantas/microbiologia , Salmonella , Solo , Fertilizantes , Humanos , Esterco , Folhas de Planta , Microbiologia do Solo , ÁguaRESUMO
Kimchi is a traditional Korean fermented food. Since it ferments continuously during distribution and storage, the extension of shelf life by preventing over-acidification is a major concern in the kimchi industry. One of the most frequently attempted ways to delay fermentation is to add naturally occurring antimicrobial agents. Many researchers have investigated ways to delay over-acidification by adding minor ingredients, fruits or fruit seed extracts, extracts of medicinal herbs, culinary herbs and spices, and other miscellaneous substances to kimchi. The addition of naturally occurring antimicrobial agents may enhance the acceptability of kimchi to consumers over a longer period of time but may also have a disadvantage in that it may cause changes in sensory quality, especially if added in large amounts. To avoid undesirable sensory changes, application of hurdle technologies (i.e., multifactor preservative systems) which involve using combinations of low amounts of various naturally occurring antimicrobial agents as ingredients should be explored with the goal of controlling fermentation. If synergistic or additive antimicrobial effects can be achieved using small amounts of a combination of natural agents, changes in sensory qualities will be minimized, thereby prolonging shelf life. Research findings summarized in this review provide a basis for developing effective hurdle technologies using naturally occurring antimicrobial agents to extend shelf life of kimchi and perhaps other types of traditional fermented foods.
Assuntos
Anti-Infecciosos/farmacologia , Brassica/microbiologia , Manipulação de Alimentos/métodos , Microbiologia de Alimentos , Brassica/química , Brassica/efeitos dos fármacos , Fermentação/efeitos dos fármacos , Controle de QualidadeRESUMO
A 1998 investigation of an outbreak of Salmonella serotype Typhimurium infections among children tasting unpasteurized milk during tours of a dairy farm demonstrated a distribution of unusually long incubation periods (median, 8 days; interquartile range [IQR], 6-14 days). Bacterial isolates were highly acid tolerant and contained genes associated with protection against destructive phagocytic reactive oxygen intermediates. We hypothesize that exposure to low-dose oral inoculum of a pathogen with these properties could have contributed to cases of non-typhoidal salmonellosis with the longest incubation period reported to the Centers for Disease Control and Prevention (CDC).