RESUMEN
Food business operators are responsible for food safety and assessment of shelf lives for their ready-to-eat products. For assisting them, a customized software based on predictive models, ListWare, is being developed. The aim of this study was to develop and validate a predictive model for the growth of Listeria monocytogenes in sliced roast beef. A challenge study was performed comprising 51 different combinations of variables. The growth curves followed the Baranyi and Roberts model with no clear lag phase and specific growth rates in the range <0.005-0.110 hr-1. A linear regression model was developed based on 528 observations and had an adjusted R-square of 0.80. The significant predictors were storage temperature, sodium lactate, interactions between sodium acetate and temperature, and MAP packaging and temperature. The model was validated in four laboratories in three countries. For conditions where the model predicted up to + log 2 cfu/g Listeria concentration, the observed concentrations were true or below the predicted concentration in 90% of the cases. For the remaining 10%, the roast beef was coated with spices and therefore different from the others. The model will be implemented in ListWare web-application for calculation of "Listeria shelf life".
Asunto(s)
Comida Rápida/microbiología , Contaminación de Alimentos/estadística & datos numéricos , Listeria monocytogenes/crecimiento & desarrollo , Productos de la Carne/microbiología , Animales , Bovinos , Contaminación de Alimentos/análisis , Inocuidad de los Alimentos , Almacenamiento de Alimentos , Cinética , Listeria monocytogenes/química , Listeria monocytogenes/genética , Listeria monocytogenes/aislamiento & purificación , Productos de la Carne/análisis , Modelos Biológicos , Análisis de Regresión , TemperaturaRESUMEN
[This corrects the article DOI: 10.1155/2017/6353510.].
RESUMEN
A prototype decision support IT-tool for the food industry was developed in the STARTEC project. Typical processes and decision steps were mapped using real life production scenarios of participating food companies manufacturing complex ready-to-eat foods. Companies looked for a more integrated approach when making food safety decisions that would align with existing HACCP systems. The tool was designed with shelf life assessments and data on safety, quality, and costs, using a pasta salad meal as a case product. The process flow chart was used as starting point, with simulation options at each process step. Key parameters like pH, water activity, costs of ingredients and salaries, and default models for calculations of Listeria monocytogenes, quality scores, and vitamin C, were placed in an interactive database. Customization of the models and settings was possible on the user-interface. The simulation module outputs were provided as detailed curves or categorized as "good"; "sufficient"; or "corrective action needed" based on threshold limit values set by the user. Possible corrective actions were suggested by the system. The tool was tested and approved by end-users based on selected ready-to-eat food products. Compared to other decision support tools, the STARTEC-tool is product-specific and multidisciplinary and includes interpretation and targeted recommendations for end-users.
Asunto(s)
Contaminación de Alimentos , Inocuidad de los Alimentos , Almacenamiento de Alimentos/normas , Industria de Procesamiento de Alimentos , Ácido Ascórbico/química , Recuento de Colonia Microbiana , Manipulación de Alimentos , Microbiología de Alimentos/normas , Humanos , Listeria monocytogenes/aislamiento & purificación , Listeria monocytogenes/patogenicidad , Listeriosis/microbiología , Listeriosis/prevención & controlRESUMEN
BACKGROUND: The genome of Bacillus licheniformis DSM 13 harbours three neighbouring open reading frames showing protein sequence similarities to the proteins encoded from the Bacillus subtilis subsp. subtilis 168 gerA operon, GerAA, GerAB and GerAC. In B. subtilis, these proteins are assumed to form a germinant receptor involved in spore germination induced by the amino acid L-alanine. RESULTS: In this study we show that disruption of the gerAA gene in B. licheniformis MW3 hamper L-alanine and casein hydrolysate-triggered spore germination, measured by absorbance at 600 nm and confirmed by phase contrast microscopy. This ability was restored by complementation with a plasmid-borne copy of the gerA locus. Addition of D-alanine in the casein hydrolysate germination assay abolished germination of both B. licheniformis MW3 and the complementation mutant. Germination of both B. licheniformis MW3 and the gerA disruption mutant was induced by the non-nutrient germinant Ca2+-Dipicolinic acid. CONCLUSIONS: These results demonstrate that the B. licheniformis MW3 gerA locus is involved in germination induced by L-alanine and potentially other components present in casein hydrolysate.
Asunto(s)
Alanina/metabolismo , Bacillus/genética , Proteínas Bacterianas/metabolismo , Proteínas de la Membrana/metabolismo , Operón , Bacillus/metabolismo , Proteínas Bacterianas/genética , Caseínas/metabolismo , Regulación Bacteriana de la Expresión Génica , Prueba de Complementación Genética , Proteínas de la Membrana/genética , Datos de Secuencia Molecular , Mutagénesis , Esporas Bacterianas/genéticaRESUMEN
Bc1245 is a monocistronic chromosomal gene of Bacillus cereus ATCC 14579 encoding a putative protein of 143 amino acids identified in this study to have a spore-related function in B. cereus. Bc1245 is highly conserved in the genome of members of the B. cereus group, indicating an important function of the gene in this group of bacteria. Quantitative PCR revealed that bc1245 is transcribed late in sporulation (upon formation of phase-bright spores) and at the same time as the mother cell-specific transcription factor σ(K) . The σ(K) regulon includes structural components of the spore (such as coat proteins), and it is therefore plausible that bc1245 might encode a structural outer spore protein. This was confirmed by detection of BC1245 in exosporium extracts from B. cereus by immunoblotting against BC1245 antiserum.
Asunto(s)
Bacillus cereus/fisiología , Proteínas Bacterianas/química , Proteínas Bacterianas/metabolismo , Esporas Bacterianas/metabolismo , Secuencia de Aminoácidos , Bacillus cereus/genética , Bacillus cereus/metabolismo , Proteínas Bacterianas/genética , Secuencia de Bases , Regulación Bacteriana de la Expresión Génica , Datos de Secuencia Molecular , Regulón , Análisis de Secuencia de ADN , Esporas Bacterianas/genética , Factores de Transcripción/química , Factores de Transcripción/genética , Factores de Transcripción/metabolismoRESUMEN
Bacillus cereus is an endospore-forming bacterium able to cause food-associated illness. Different treatment processes are used in the food industry to reduce the number of spores and thereby the potential of foodborne disease. Chitosan is a polysaccharide with well-documented antibacterial activity towards vegetative cells. The activity against bacterial spores, spore germination and subsequent outgrowth and growth (the latter two events hereafter denoted (out)growth), however, is poorly documented. By using six different chitosans with defined macromolecular properties, we evaluated the effect of chitosan on Bacillus cereus spore germination and (out)growth using optical density assays and a dipicolinic acid release assay. (Out)growth was inhibited by chitosan, but germination was not. The action of chitosan was found to be concentration-dependent and also closely related to weight average molecular weight (M(w)) and fraction of acetylation (F(A)) of the biopolymer. Chitosans of low acetylation (F(A)=0.01 or 0.16) inhibited (out)growth more effectively than higher acetylated chitosans (F(A)=0.48). For the F(A)=0.16 chitosans with medium (56.8kDa) and higher M(w) (98.3kDa), a better (out)growth inhibition was observed compared to low M(w) (10.6kDa) chitosan. The same trend was not evident with chitosans of 0.48 acetylation, where the difference in activity between the low (19.6kDa) and high M(w) (163.0kDa) chitosans was only minor. In a spore test concentration corresponding to 10(2)-10(3)CFU/ml (spore numbers relevant to food), less chitosan was needed to suppress (out)growth compared to higher spore numbers (equivalent to 10(8)CFU/ml), as expected. No major differences in chitosan susceptibility between three different strains of B. cereus were detected. Our results contribute to a better understanding of chitosan activity towards bacterial spore germination and (out)growth.
Asunto(s)
Antibacterianos/farmacología , Bacillus cereus/efectos de los fármacos , Bacillus cereus/fisiología , Quitosano/farmacología , Microbiología de Alimentos , Esporas Bacterianas/efectos de los fármacos , Bacillus cereus/clasificación , Infecciones Bacterianas/prevención & control , Quitosano/químicaRESUMEN
During the course of screening Bacillus species from food and water in Norway, we isolated a strain of Bacillus sphaericus of DNA homology group V, not previously recognized to contain entomopathogenic strains, that was cytotoxic to Vero cell epithelia. Peptide mass fingerprinting of a protein purified from the culture supernatant of B. sphaericus B354 identified a cholesterol-dependent cytolysin (CDC) with high amino acid sequence identity with sphaericolysin, a CDC identified recently in B. sphaericus DNA homology group IIA. The toxin was haemolytic against erythrocytes from a range of species. Haemolysis was potentiated by dithiothreitol and inhibited by preincubation with cholesterol. The toxin induced lactate dehydrogenase release from Vero cells and formed pores in planar lipid bilayers. The distribution of CDC genes in B. sphaericus was examined, with CDC gene products obtained in 13 out of 17 strains representing four of the six DNA homology groups. Thus, we demonstrate the presence of a CDC in a nonentomopathogenic DNA homology group of B. sphaericus (group V) with typical CDC characteristics. CDCs appear to be present in a high proportion of B. sphaericus strains and are not restricted to group IIA insecticidal strains.
Asunto(s)
Bacillus/metabolismo , Proteínas Bacterianas/metabolismo , Colesterol/metabolismo , Proteínas Hemolisinas/metabolismo , Animales , Bacillus/química , Bacillus/genética , Bacillus/aislamiento & purificación , Proteínas Bacterianas/química , Proteínas Bacterianas/genética , Proteínas Bacterianas/farmacología , Bovinos , Chlorocebus aethiops , Eritrocitos/efectos de los fármacos , Infecciones por Bacterias Grampositivas/metabolismo , Proteínas Hemolisinas/química , Proteínas Hemolisinas/genética , Proteínas Hemolisinas/farmacología , Caballos , Membrana Dobles de Lípidos/metabolismo , Datos de Secuencia Molecular , Homología de Secuencia de Aminoácido , Ovinos , Células VeroRESUMEN
Food poisoning caused by other Bacillus species than B. cereus has been described, but the toxins involved have rarely been isolated. Endospores will survive heat treatment and will germinate and multiply in cooked foods producing toxins under appropriate conditions. We describe a small food poisoning outbreak where three people became ill after a dinner in a Chinese restaurant. Acute symptoms including dizziness, headache, chills and back pain developed during the meal, and a few hours later they got stomach cramps and diarrhoea which lasted for several days. Cooked, reheated rice was the prime suspect of the food poisoning, and from the rice large numbers of Bacillus pumilus were isolated. The isolated B. pumilus strain was found to produce a complex of lipopeptides known as pumilacidins with the highest amounts produced at 15 degrees C. This is the first report on isolation of a pumilacidin-producing B. pumilus strain from food implicated in food poisoning and characterization of the organism and the toxin complex involved.
Asunto(s)
Bacillus/metabolismo , Contaminación de Alimentos/análisis , Enfermedades Transmitidas por los Alimentos/epidemiología , Oryza/microbiología , Péptidos/envenenamiento , Brotes de Enfermedades , Femenino , Microbiología de Alimentos , Humanos , Masculino , Noruega/epidemiologíaRESUMEN
A total of 333 Bacillus spp. isolated from foods, water, and food plants were examined for the production of possible enterotoxins and emetic toxins using a cytotoxicity assay on Vero cells, the boar spermatozoa motility assay, and a liquid chromatography-mass spectrometry method. Eight strains produced detectable toxins; six strains were cytotoxic, three strains produced putative emetic toxins (different in size from cereulide), and one strain produced both cytotoxin(s) and putative emetic toxin(s). The toxin-producing strains could be assigned to four different species, B. subtilis, B. mojavensis, B. pumilus, or B. fusiformis, by using a polyphasic approach including biochemical, chemotaxonomic, and DNA-based analyses. Four of the strains produced cytotoxins that were concentrated by ammonium sulfate followed by dialysis, and two strains produced cytotoxins that were not concentrated by such a treatment. Two cultures maintained full cytotoxic activity, two cultures reduced their activity, and two cultures lost their activity after boiling. The two most cytotoxic strains (both B. mojavensis) were tested for toxin production at different temperatures. One of these strains produced cytotoxin at growth temperatures ranging from 25 to 42 degrees C, and no reduction in activity was observed even after 24 h of growth at 42 degrees C. The strains that produced putative emetic toxins were tested for the influence of time and temperature on the toxin production. It was shown that they produced putative emetic toxin faster or just as fast at 30 as at 22 degrees C. None of the cytotoxic strains produced B. cereus-like enterotoxins as tested by PCR or by immunological methods.