Biomedical subjects

F M Rombouts

Publications and source records attributed to F M Rombouts.

At least 19 recordsLinked to original sources

PubMed2006

Effect of osmolality on net fluid absorption in non-infected and ETEC-infected piglet small intestinal segments.

In the small intestinal segment perfusion model the effect of osmolality on net fluid absorption in enterotoxigenic Escherichia coli (ETEC)-infected and non-infected small intestinal segments of piglets was investigated. In ETEC-infected segments net fluid absorption was reduced. Lowering the osmolality from 375 to 150 mOsmol/l by reducing sodium chloride concentrations increased net fluid absorption. There was a linear relationship between osmolality and net fluid absorption for both non-infected and ETEC-infected segments. Below 150 mOsmol/l the inverse relationship between osmolality and net fluid absorption disappeared. Substitution of sodium chloride with mannitol decreased net fluid absorption since mannitol cannot be actively absorbed. In ETEC-infected segments perfused with oral rehydration solution net fluid absorption significantly increased compared to a sodium chloride solution of similar osmolality, probably because of the high glucose concentration. Supplying hypotonic sodium chloride fluids to piglets can be beneficial in replenishing water and electrolyte losses in case of infectious diarrhoea.

Animals↗

PubMed2006

Mortality and growth performance of broilers given drinking water supplemented with chicken-specific probiotics.

For application in broiler production, we developed a multispecies (MSPB) and a chicken-specific (CSPB) probiotic preparation in fluid form. The MSPB contained different probiotic species of human origin, whereas the CSPB consisted of 7 Lactobacillus species isolated from the digestive tract of chickens. In a field trial with broilers, MSPB treatment resulted in a slight increase (by 1.84%) in broiler productivity based on an index taking into account daily weight gain, feed efficiency, and mortality. The CSPB treatment reduced mortality in 2 subsequent field trials and raised productivity by 2.94 and 8.70%. In a controlled trial with broilers showing a high index of productivity, probiotic treatment further raised productivity by 3.72%. Based on the present 4 studies in combination with 9 studies published earlier, it is suggested that with higher productivity rates of the broilers the effect of probiotics becomes smaller.

Animals↗

PubMed2006

Prevalence of potentially pathogenic Bacillus cereus in food commodities in The Netherlands.

Randomly selected food commodities, categorized in product groups, were investigated for the presence and number of Bacillus cereus bacteria. If positive, and when possible, five separate colonies were isolated and investigated for the presence of four virulence factors: presence of genes encoding three enterotoxins (hemolysin BL [HBL], nonhemolytic enterotoxin [NHE], and cytotoxin K) and the ability to produce cereulide. In addition, the presence of psychrotrophic and mesophilic signatures was determined. The genes for NHE are found in more than 97% of the isolates, those for HBL in approximately 66% of the isolates, and the gene for cytotoxin K in nearly 50% of the isolates. Significant associations between product groups and (combinations of) virulence factors were the relatively low percentage of isolates from the "flavorings" group containing genes encoding NHE and the higher-than-average occurrence of both the genes encoding HBL and NHE in the "pastry" group. Cereulide was produced by 8.2% of the isolates but only in combination with the presence of genes for one or more other virulence factors. Most isolates (89.9%) were mesophilic; minorities of the isolates were psychrotrophic (4.4%) or of intermediate signature (5.7%). In the product group "milk and milk products," the incidence of strains with psychrotrophic or intermediate signatures is significantly higher than in the other product groups. In the product groups "flavorings," "milk and milk products," "vegetable(s) and vegetable products," "pastry," and "ready-to-eat foods," a relatively high number of samples contain high numbers of B. cereus bacteria. Within the product group "ready-to-eat foods," the products containing rice and pasta show a relatively high incidence of high numbers of B. cereus bacteria.

Animals↗

PubMed2005

Functionality of selected strains of moulds and yeasts from Vietnamese rice wine starters.

The role of starch-degrading mycelial fungi, and the alcohol production and ethanol tolerance of the yeasts isolated from selected Vietnamese traditional rice wine starters were examined, and optimum conditions for these essential steps in rice wine fermentation were determined. Of pure isolates from Vietnamese rice wine starters, mould strains identified as Amylomyces rouxii, Amylomyces aff. rouxii, Rhizopus oligosporus and Rhizopus oryzae, were superior in starch degradation, glucose production and amyloglucosidase activity during the saccharification of purple glutinous rice. A. rouxii was able to produce up to 25%w/w glucose with an amyloglucosidase activity up to 0.6 Ug(-1) of fermented moulded mass. Five yeast isolates identified as Saccharomyces cerevisiae were selected for their superior alcohol productivity. They were able to deplete a relatively high initial percentage of glucose (20% w/v), forming 8.8% w/v ethanol. The ethanol tolerance of S. cerevisiae in challenge tests was 9-10% w/v, and 13.4% w/v as measured in fed-batch fermentations. Optimum conditions for the saccharification were: incubation for 2 d at 34 degrees C, of steamed rice inoculated with 5 log cfu g(-1); for the alcoholic fermentation 4 d at 28.3 degrees C, of saccharified rice liquid inoculated with 5.5 log cfu mL(-1).

Colony Count, Microbial↗

PubMed2005

Effect of individual amino acids and glucose on activation and germination of Rhizopus oligosporus sporangiospores in tempe starter.

AIM: To understand the conditions promoting activation and germination of spores, and to contribute to the control of tempe starters. METHODS AND RESULTS: Using microscopic counts of fluorescent labelled spores, the following results were obtained: (1) L-alanine plays an important role (of the same order as that of peptone) in stimulation of germination of dormant spores. Alanine can satisfy the requirements of carbon as well as nitrogen for spore germination; (2) L-proline, on the other hand, inhibits alanine uptake presumably by blocking/congesting transporters of spore cells, resulting in apparent low viability on agar media; (3) L-leucine and L-isoleucine slightly favour spore germination while L-arginine and L-lysine do not have any stimulating effect; (4) The stimulatory role of glucose was only evident in the presence of phosphate (in minimal medium); when glucose is used in the absence of phosphate, either alone or in combination with single amino acids its role is hardly distinguishable; (5) Phosphate plays a facilitating role in spore germination. CONCLUSIONS: Glucose and amino acids play important roles in activation and germination of sporangiospores of Rhizopus oligosporus in tempe starter (stored for 12 months). The ability and rate of germination of dormant/old sporangiospores of R. oligosporus, depend on their ability for uptake of individual amino acids and/or glucose. SIGNIFICANCE AND IMPACT OF STUDY: New light was shed on the counteractive role of proline and the stimulating effect of phosphate. Soybeans subjected to traditional preparation for tempe making are heavily leached; germination of starter spores on such beans is sub-optimal, and bean processing could be optimized.

Alanine↗

PubMed2005

Health and growth of veal calves fed milk replacers with or without probiotics.

Four experiments with 1-wk-old veal calves were conducted to assess the influence of probiotics on growth and health indicators. In experiments 1 and 2, the liquid probiotic supplements were administered daily from experimental d 1 to 15. The treatment period in experiments 3 and 4 was extended to 56 d. The probiotics used were a multispecies probiotic (MSPB) containing different probiotic species of human origin, or a calf-specific probiotic (CSPB) containing 6 Lactobacillus species isolated from calf feces and selected on the basis of a combination of characteristics. When the data for the 4 experiments were pooled, the probiotics enhanced growth rate during the first 2 wk. During the 8-wk experimental period, average daily gain and feed efficiency were significantly improved in the probiotic-treated groups. The MSPB-induced increase in weight gain was greater when the control calves were considered less healthy based on a health score (an index of diarrhea and therapeutic treatments). Probiotic treatment tended to diminish mortality. The CSPB treatment reduced the incidence of diarrhea and the fecal counts of coliforms. When therapeutic treatment was intensive in the control calves, the ingestion of probiotics reduced the percentage of calves that required therapy and the amount of treatments needed against digestive or respiratory diseases. There was no clear difference in the efficiency of the MSPB and CSPB preparations. Further research is necessary to identify underlying mechanisms and to evaluate the potential of probiotics to improve respiratory health in veal calf production.

Animals↗

PubMed2005

Gut flora in health and disease: potential role of probiotics.

In a young evolving science, there are always more questions than answers. That is also the situation in the emerging field of Probiotics, and this was made very clear at the International Probiotics Workshop in Amsterdam. In the report of this workshop, we present a selection of the most urgent questions in the field of probiotics. In addition, we propose a few strategies for the future of probiotics research. During the workshop, 120 experts--from disciplines including Human Nutrition, Gastroenterology, Nutritional Therapy, Cell Biology, Microbiology and Immunology--discussed new views on microbe-host interactions and the role of probiotics in prevention and alleviation of gastro-intestinal, atopic and auto-immune diseases. There is a general consensus among the experts that administering defined strains can help in preventing and curing gut flora related diseases: the first clinical trials show a promising role for probiotics. But the system is very complex, and most underlying mechanisms are still unclear. Rapid progress in this field will depend largely on the collaboration between fundamental researchers from different disciplines and medical specialists. Besides, more clinical studies are required to convince authorities and the public of the value of microbial therapies.

Animals↗

PubMed2004

Behavior of Clostridium perfringens at low temperatures.

Refrigerated storage is an important step in the preparation of foods and inadequate storage is one of the main causes of food poisoning outbreaks of Clostridium perfringens. Therefore, growth and germination characteristics of C. perfringens in a temperature range of 3-42 degrees C were determined in fluid thioglycollate broth (FTG) and Dutch pea soup. To study the effect of adaptation, cells were either inoculated from a 37 degrees C pre-culture or from a temperature-adapted pre-culture. Membrane fatty acid patterns were determined at all temperatures to examine the effect of temperature on membrane composition. Spores were either inoculated with and without heat treatment. Adaptation of cells did not influence growth rate nor lag phase. Growth in pea soup, however, was slower and lag phases tended to be more extended compared to FTG. No growth was observed at temperatures < or =10 degrees C and death rates in pea soup were higher than those in FTG at these low temperatures. Cells preserved the membrane fluidity by reducing the arachidic acid content and increasing the lauric acid content when the temperature dropped. This resulted in a net reduction in chain length. Microscopic analysis of cells grown at 15 degrees C revealed a morphological change: cells were elongated compared to those grown at 37 degrees C. These data demonstrate the ability of C. perfringens to adapt to lower temperatures. However, this did not influence growth characteristics compared to non-adapted cells. Spores of C. perfringens did germinate at all temperatures with and without heat-activation. Combining this fact with the extended survival at low temperatures emphasizes the need for adequate heating of refrigerated foods before consumption to eliminate health risks due to C. perfringens.

Adaptation, Physiological↗

PubMed2004

Monostrain, multistrain and multispecies probiotics--A comparison of functionality and efficacy.

This literature review was carried out to make a comparison of functionality and efficacy between monostrain, multistrain and multispecies probiotics. A monostrain probiotic is defined as containing one strain of a certain species and consequently multistrain probiotics contain more than one strain of the same species or, at least of the same genus. Arbitrarily, the term multispecies probiotics is used for preparations containing strains that belong to one or preferentially more genera. Multispecies probiotics were superior in treating antibiotic-associated diarrhea in children. Growth performance and particularly mortality in broilers could be improved with multistrain probiotics. Mice were better protected against S. Typhimurium infection with a multistrain probiotic. A multispecies probiotic provided the best clearance of E. coli O157:H7 from lambs. Rats challenged with S. Enteritidis showed best post-challenge weight gains when treated with a multispecies probiotic. Possible mechanisms underlying the enhanced effects of probiotic mixtures are discussed. It is also emphasized that strains used in multistrain and multispecies probiotics should be compatible or, preferably, synergistic. The design and use of multistrain and multispecies probiotics should be encouraged.

Animals↗

PubMed2004

Effect of cooling on Clostridium perfringens in pea soup.

Foods associated with Clostridium perfringens outbreaks are usually abused after cooking. Because of their short generation times, C. perfringens spores and cells can grow out to high levels during improper cooling. Therefore, the potential of C. perfringens to multiply in Dutch pea soup during different cooling times was investigated. Tubes of preheated pea soup (50 degrees C) were inoculated with cocktails of cells or heat-activated spores of this pathogen. The tubes were linearly cooled to 15 degrees C in time spans of 3, 5, 7.5, and 10 h and were subsequently stored in a refrigerator at 3 or 7 degrees C for up to 84 h. Cell numbers increased by 1-log cycle during the 3-h cooling period and reached their maximum after 10 h of cooling. Subsequent refrigeration hardly reduced cell numbers. Cooling of 3.75 liters of pea soup in an open pan showed that this amount of pea soup cooled from 50 to 15 degrees C in 5 h, which will allow a more than 10-fold increase in cell numbers. These findings emphasize the need of good hygienic practices and quick cooling of heated foods after preparation.

Clostridium perfringens↗

PubMed2003

Comparison of media for enumeration of Clostridium perfringens from foods.

Many media have been developed to enumerate Clostridium perfringens from foods. In this study, six media [iron sulfite (IS) agar, tryptose sulfite cycloserine (TSC) agar, Shahidi Ferguson perfringens (SFP) agar, sulfite cycloserine azide (SCA), differential clostridial agar (DCA), and oleandomycin polymyxin sulfadiazine perfringens (OPSP) agar] were compared in a prestudy, of which four (IS, TSC, SCA, and DCA) were selected for an international collaborative trial. Recovery of 15 pure strains was tested in the prestudy and recovery of one strain from foodstuffs was tested in the collaborative trial. Results from the prestudy did reveal statistical difference of the media but recoveries on all media were within the microbiological limits (+/-30%) of IS, which was set as a reference medium. Recoveries on the media tested in the collaborative trial were statistically different as well, but these differences were of no microbiological-analytical relevance. Food matrices did not affect the recovery of C. perfringens in general. DCA and SCA, in particular, are labor-intensive to prepare and DCA frequently failed to produce black colonies; gray colonies were quite common. Since IS medium is nonselective, it was concluded that TSC was the most favorable medium for the enumeration of C. perfringens from foods.

Animals↗

PubMed2003

An antifungal compound produced by Bacillus subtilis YM 10-20 inhibits germination of Penicillium roqueforti conidiospores.

AIMS: To identify and characterize an antifungal compound produced by Bacillus subtilis YM 10-20 which prevents spore germination of Penicillium roqueforti. METHODS AND RESULTS: The antifungal compound was isolated by acid precipitation with HCl. This compound inhibited fungal germination and growth. Identification by HPLC and mass spectrometry analysis showed high similarity to iturin A. Permeabilization and morphological changes in P. roqueforti conidia in the presence of the inhibitor were revealed by fluorescence staining and SEM, respectively. CONCLUSOINS: The iturin-like compound produced by B. subtilis YM 10-20 permeabilizes fungal spores and blocks germination. SIGNIFICANCE AND IMPACT OF THE STUDY: Fluorescence staining in combination with flow cytometry and scanning electron microscopy are efficient tools for assessing the action of antifungal compounds against spores. Iturin-like compounds may permeabilize fungal spores and inhibit their germination.

Antifungal Agents↗

PubMed2003

Effect of fermented soya beans on diarrhoea and feed efficiency in weaned piglets.

AIMS: To evaluate anti-diarrhoeal and growth enhancing properties of fermented soya beans in weaned piglets. METHODS AND RESULTS: In a first phase piglet diet, toasted full-fat soya beans (20%) were replaced with either cooked soya beans or Rhizopus microsporus or Bacillus subtilis fermented soya beans. The effect on the incidence, severity and duration of diarrhoea in enterotoxigenic Escherichia coli (ETEC)-challenged weaned piglets was determined (pen trial, 24 piglets per treatment). Severity of diarrhoea was significantly less on the diet with Rhizopus-fermented soya beans compared with the control diet containing toasted soya beans. Piglets fed fermented soya beans showed increased feed intake (13 and 12%), average daily weight gain (18 and 21%) and feed efficiency (3 and 8%) (for Rhizopus and Bacillus-fermented soya beans, respectively). However, in the treatment groups an unequal mortality and a potential unequal distribution of receptor-positive piglets were observed. CONCLUSIONS: Cooked and fermented soya beans could be beneficial in the control of diarrhoea in ETEC-challenged weaned piglets (particularly Rhizopus fermented) and significantly improved weight gain and feed intake (particularly Bacillus fermented). SIGNIFICANCE AND IMPACT OF THE STUDY: Fermented soya beans could offer benefits with respect to the control of diarrhoea and feed efficiency in piglets.

Animal Feed↗

PubMed2003

Tolerance of Salmonella Enteritidis and Staphylococcus aureus to surface cleaning and household bleach.

Effective cleaning and sanitizing of food preparation sites is important because pathogens are readily spread to food contact surfaces after preparation of contaminated raw products. Tolerance of Salmonella Enteritidis and Staphylococcus aureus to surface cleaning by wiping with regular, microfiber, and antibacterial-treated cloths was investigated. Wiping with cleaning cloths resulted in a considerable reduction of microorganisms from surfaces, despite the greater difficulty in removing S. aureus than Salmonella Enteritidis. Depending on the cloth type, S. aureus were reduced on surfaces from initial numbers of approximately 10(5) CFU/100 cm2 to numbers from less than 4 CFU/100 cm2 (below the detection limit) to 100 CFU/100 cm2. Directly after the cloths were used to clean the contaminated surfaces, they contained high numbers of bacteria (10(4) to 10(5) CFU/100 cm2), except for the disposable antibacterial-treated cloths, in which no bacteria could be detected. The tolerance of these pathogens to sodium hypochlorite was studied in the suspension test and in cloths. S. aureus showed a better tolerance for sodium hypochlorite than Salmonella Enteritidis. Inactivation of microorganisms in cloths required a higher concentration of sodium hypochlorite than was needed in the suspension test. Repeated exposure to sodium hypochlorite, however, resulted in an increase in susceptibility to this compound. This study provides essential information about the transfer of bacteria when wiping surfaces and highlights the need for a hygiene procedure with cleaning cloths that sufficiently avoids cross-contamination in the household environment.

Bacterial Adhesion↗

PubMed2003

Selection of fluorescent probes for flow cytometric viability assessment of Listeria monocytogenes exposed to membrane-active and oxidizing disinfectants.

The aim of this study was to select fluorescence methods for use as alternatives to plate counting to assess the viability of Listeria monocytogenes cells exposed to benzalkonium chloride (BAC) and hydrogen peroxide, two disinfectants with different mechanisms of action. A further aim of this study was to determine whether growth phase influences fluorescence labeling and whether it is possible to predict whether a probe will be a good viability indicator for cells exposed to a certain disinfectant on the basis of the mechanism of action of the disinfectant and the target of the fluorescent probe. The fluorescence methods used were labeling with 5-cyano-2,3-ditolyl tetrazolium chloride (CTC; dehydrogenase activity), labeling with TOTO-1 iodide (TOTO; membrane-impermeant probe), and assessment of pH gradient maintenance in a low-pH buffer after labeling with the pH-sensitive probe 5-(and 6)-carboxyfluorescein succinimidyl ester (CFSE) (the pH(in) method). Growth phase influenced fluorescent labeling. However, the cutoff value for distinction between viable and nonviable cells was the same for both growth phases. The viability (determined by plate counts) of BAC-exposed cells correlated well with CTC labeling and TOTO exclusion. For both BAC-exposed and hydrogen peroxide-exposed cells, the pH(in) method gave a good qualitative indication of viability, sublethal damage, and cell death. CTC labeling and TOTO exclusion did not correlate with the viability of hydrogen peroxide-exposed cells. Our results demonstrate that even if the mechanism of action of a disinfectant is known, in some cases it is still difficult to predict whether a certain fluorescent probe is suitable for viability assessment. Thus, the proper selection of fluorescent probes for the assessment of the efficacy of antimicrobial agents is essential.

Benzalkonium Compounds↗

PubMed2002

Inhibition of adhesion of enterotoxigenic Escherichia coli K88 by soya bean tempe.

AIMS: Tempe is a traditional fungal fermented food made from soaked and cooked soya beans. It has been associated with antidiarrhoeal characteristics. This study investigated potential inhibitory effects of tempe on enterotoxigenic Escherichia coli (ETEC) K88. METHODS AND RESULTS: Soya beans were soaked, cooked and subsequently fermented using several Rhizopus spp. Water-soluble filter-sterile extracts were tested for their ability to inhibit growth of E. coli and several indicator microorganisms and to inhibit adhesion of ETEC K88. Antimicrobial activity was found against Bacillus stearothermophilus only. ETEC K88-induced haemagglutination of hamster red blood cells was strongly inhibited by a number of tempe extracts and hardly by the cooked soya bean extract. Furthermore, several tempe extracts were able to inhibit adhesion of ETEC K88 to piglet small intestinal brush-border membranes. CONCLUSIONS: Tempe appeared to interfere with ETEC K88 adhesion rather than showing growth inhibitory properties. SIGNIFICANCE AND IMPACT OF THE STUDY: The results indicate that tempe could exert an antagonistic effect against ETEC through inhibition of adhesion and might therefore have a protective effect against ETEC K88 infection in pigs. Hence, tempe could have potential to use as a feed supplement in the diet of weaned piglets.

Animals↗

PubMed2002

The effect of the growth phase of Staphylococcus aureus on resistance to disinfectants in a suspension test.

The influence of growth phase on the resistance of Staphylococcus aureus to the surface-active agents benzalkonium chloride and dodecylbenzyl sulfonic acid and the oxidizing agents sodium hypochlorite and hydrogen peroxide was studied. The resistances of cells in different growth phases were compared to those of solid medium cells grown according to the European phase I suspension test. Using cells from different growth phases (+/- 3 x 10(7) CFU ml(-1)), we found that decline-phase cells were the most resistant cells. However, the decline-phase cell suspension contained more than 90% dead cells. A 10-fold-diluted suspension with a total concentration of cells equal to that of the other cell suspensions still revealed decline-phase cells to be generally the most resistant cell type. However, the resistance was drastically reduced, indicating that the large proportion of dead cells provided significant protection to the viable decline-phase cells. Hydrogen peroxide resistance could be partly explained by the high catalase activity in the dead-cell fraction. Exponential-phase cells were less resistant than decline-phase cells, and, surprisingly, stationary-phase cells were the least resistant of the three. Cells grown according to the European phase 1 suspension test were never the most resistant cells. Their survival was 1 to 3 log units lower than that of the most resistant cells. These findings show that the solid-medium cells currently used in disinfectant tests are not the most resistant cells that can be used.

Catalase↗

PubMed2002

Effects of antibacterial dishwashing liquid on foodborne pathogens and competitive microorganisms in kitchen sponges.

In response to increasing concern about home hygiene, the use of antibacterial products to reduce microorganisms in kitchen sponges and cleaning cloths is strongly promoted by some producers of detergent for domestic use. The effects of an antibacterial dishwashing liquid on Escherichia coli, Salmonella Enteritidis, Staphylococcus aureus, and Bacillus cereus were investigated in a modified suspension test and in used sponges with and without food residues under laboratory conditions. A limited study was conducted in households to assess the efficacy of antibacterial dishwashing liquid as used by the consumer. In the suspension tests, S. aureus and B. cereus were shown to be susceptible to low concentrations of antibacterial dishwashing liquid (0.5%), whereas E. coli and Salmonella Enteritidis maintained their initial numbers for at least 24 h at 25 degrees C. At higher concentrations (2 to 4%), all test organisms decreased to below the detection limit after 24 h. Over a 24-h period, the antibacterial dishwashing liquid did not significantly reduce these organisms in used sponges in which food residues were present. The antibacterial product did not reduce the competitive microorganisms either. Similar results were found for sponges involved in daily household use. The results of this study demonstrate that the antibacterial dishwashing liquid was effective in reducing pathogens in the suspension test but not in the used sponges. This finding indicates that to determine the efficacy of antibacterial products, their use in a household setting must be considered.

Bacillus cereus↗