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Biomedical subjects

D A Mossel

Publications and source records attributed to D A Mossel.

At least 37 records · Page 2Linked to original sources
PubMed1994

The immediate bactericidal effect of lactic acid on meat-borne pathogens.

The kinetics of the bactericidal effect of lactic acid decontamination (LAD) on meat-borne pathogens (Salmonella spp., Campylobacter jejuni and Listeria monocytogenes) was studied in an in-vitro model. The bactericidal effect was greatest on organisms in the lactic acid film that replaced the natural fluid on the meat surface during LAD. A stepwise increase in pH from 2.6 to 3.5 and 4.0 progressively reduced the bactericidal effect of decontamination. For treatment with 2% lactic acid for 30-90 s at 21 degrees C, the immediate death of Salmonella spp. decreased from about 0.5-2 log10 cfu at pH 2.6 to an insignificant level at pH 4.0. The immediate death for Camp. jejuni decreased from 2.6 to > 5.3 at pH 2.6 to 0.3-1.0 at pH 4.0. The decrease in bactericidal effect with increasing pH could, however, be countered by an increase in the temperature from 21 degrees C to 37 degrees C. It is suggested that 2% LAD at 37 degrees C for 30-90 s is suitable for elimination of salmonellas on meat but not for L. monocytogenes. Decontamination with 1% lactic acid at pH 3.0 and 21 degrees C for at least 30 s was effective for Camp. jejuni. Mesophilic Enterobacteriaceae were reliable indicators of the LAD-induced bactericidal effect on Salmonella spp. and Camp. jejuni.

Buffers↗
PubMed1994

An in-vitro meat model for the immediate bactericidal effect of lactic acid decontamination on meat surfaces.

An in-vitro model of the lactic acid decontamination (LAD) of meat is described. As LAD is a disinfection rather than a preservation process the model is based on the inactivation kinetics of bacteria in a suspension of pork skin. The model takes account of interfering factors present in nature, such as microbial interactions, leaching of organic material from the meat surfaces and buffering activity.

Animals↗
PubMed1993

Assessment of cleaning and disinfection in the food industry with the rapid ATP-bioluminescence technique combined with the tissue fluid contamination test and a conventional microbiological method.

A quantitative ATP bioluminescence procedure has been used to determine the cleanliness of food processing factories and the results have been compared with those from conventional microbiological culture methods. ATP measurements were combined with the tissue or tissue fluid contamination (TTFC) assessment method to obtain an impression of the amount of inanimate contamination on the sampled surfaces. It was found that, in the sampled food factories, there was poor relation between the two assessment techniques: ATP bio-luminescence combined with TTFC and contact plating. However, either method in its own right is useful to check cleanliness of food industries. ATP measurements do have in addition the great advantage that it is a fast method and is easy to perform.

Adenosine Triphosphate↗
PubMed1991

[Cholera pandemic hits South America. Consequences for The Netherlands as import country of food and animal food].

The cholera-pandemic raging in South-America calls for measures of health protection with respect to citizens of countries importing food or feed components from the areas where the disease has struck. Instead of ruggedly barring importation a more humanitarian policy is recommended, relying on assistance with the introduction of and adherence to rigorous measures of longitudinally integrated microbiological safety assurance, to be monitored in cooperation with importing countries. Examples of how canned foods of neutral pH, fishery products, vegetables, fruits and fishmeal should be processed-for-safety for this purpose are presented.

Animal Feed↗
PubMed1991

Public health implication of refrigerated pasteurized ('sous-vide') foods.

Food that upon pasteurization is stored in hermetically sealed containers at food temperatures not exceeding 3 degrees C could be designated by the generic term Refrigerated Pasteurized Foods of Extended Durability, REPFEDs. If not properly processed or protected against recontamination, or if temperature-abused, REPFEDs may present serious health risks. However, control is readily available. Sound microbial ecology, supported by expert risk assessment, allows the design and introduction of longitudinally integrated manufacture, distribution, handling by outlets and consumers and culinary preparation, which result in the assurance of the wholesomeness of the commodity as eaten. Recent progress, including intrinsic preservation by the incorporation of starter cultures, bacteriocins or particular enzymes, opens vistas for attractive future developments. Once microbiological safety has been built into the REPFED-line, monitoring can be limited to (i) real-time tests particularly applied to the factory environment; and (ii) rapid, simple examination for marker organisms of freshly manufactured products versus those approaching expiration dates. Such audits will allow rapid retrieval of incidental process failure and its rectification. It also serves to substantiate measurements of food temperature and spot checks on intrinsic inhibitory attributes. The application of scientific knowledge and technological expertise should primarily be entrusted to the industry itself, heeding Lord Plumb's strategy of "partnership along the food production chain from farm to fork." It should be supported and validated by Public Health Authorities. At all stages safety communication with the public should be ensured.

Bacteria↗
PubMed1991

Selective enumeration of spores of Clostridium species in dried foods.

The suitability of a variety of media and procedures for the enumeration of sulphite-reducing clostridia in food was investigated. The most suitable procedure was pasteurization of the 1/10 macerate for at least 1 min at 80 degrees C; followed by culture at 30 degrees C for up to 3 d in a sulphite-based, differential reinforced clostridium medium, without bicarbonate or lactate but with an increased iron concentration, and sulphite and iron added after sterilization. Black sulphite-reducing colonies were finally tested for sensitivity to metronidazole and confirmation of their failure to grow on agar slopes under aerobic conditions.

Animals↗
PubMed1990

[The veterinarian active in the field of veterinary public health, towards the year 2000].

Introductory classes taught to seventeen successive generations of postgraduate veterinary students, intensive consultations, during about 40 years, with scientists in executive positions in the food industry, catering and military-medical organisations, and the response of participants after public lectures support the impression that, in the Netherlands, the public is not aware of the professional profile of the Public Health Veterinarian. This contrasts sharply to that of the small animal practitioner and of the herd management veterinarian. In the years immediately before the Second World War the professional standing of the Veterinary Public Health Officer was demonstrably better observable. The reason for this altered public image of the Public Health Veterinarian is sought in changes in the aetiology and transmission of zoonoses and other diseases spread by food, water and the environment. Whereas the majority of the latter was previously transmitted off intra vitam foci of infection, food-borne infections and intoxications presently mainly originate from the environment. Consequently adequate protection of the consumer has to rely on the elaboration and application of measures of intervention sensu Wilson. These include: well designed techniques of hygiene supported by disinfection at the farm and during transportation and holding animals for slaughter, use of probiotics in decontaminated animal feeds, meticulous adherence to expertly designed measures of hygiene and chilling at slaughter houses and, to the extent required, terminal decontamination of carcasses and/or consumer size cuts. Many of these facets do not traditionally belong to the veterinarian's vistas.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Psychrotrophic strains of Bacillus cereus producing enterotoxin.

In investigations on three outbreaks of Bacillus cereus food poisoning in Spain and The Netherlands, the causative strains grew within a temperature range of 4-37 degrees C, but not at 43 degrees C. Such psychrotrophic types were found to occur in various dairy products (including ca 25% of 35 samples of pasteurized milk) and some mousses and cook/chill meals. Growth of and enterotoxin production by psychrotrophic B. cereus could be prevented by temperatures below 4 degrees C and pH-values not exceeding 5.0.

Bacillus cereus↗
PubMed1989

Liquid and solid selective differential media for the detection and enumeration of L. monocytogenes and other Listeria spp.

A selective and differential medium (PALCAM agar) was elaborated for the isolation and enumeration of Listeria monocytogenes. PALCAM is based on Columbia agar with 0.05% glucose made selective by the addition of 0.001% polymyxin B, 0.0005% acriflavin, 1.5% lithium chloride and 0.002% ceftazidime. The diagnostic traits were attained by the incorporation of (i) 0.08% aesculin and 0.05% ferric salt; and (ii) 1% mannitol plus 0.008% phenol red. PALCAM recovered test strains of L. monocytogenes and other Listeria spp quantitatively and suppressed most other bacteria of common occurrence in fresh food. L. monocytogenes colonies were approximately 2 mm grey-green with a black sunken centre and a black halo on a cherry-red background. The occasional Enterococcus or Staphylococcus strains developing on the medium gave rise to grey colonies with a brown-green halo or yellow colonies with a yellow halo. PALCAM was the preferred medium out of 13 tested Listeria selective agars in current use. A similar differential enrichment broth, L-PALCAMY was developed based on peptone yeast extract broth with 2.5% egg yolk emulsion. The diagnostic traits and inhibitors used in this medium were the same as in PALCAM agar, through in different concentrations. Growth rate and cellcrop of L. monocytogenes in L-PALCAMY were of the same order as in Columbia broth. The growth of the majority of other bacteria of common occurrence in fresh foods was inhibited. The medium recovered L. monocytogenes more effectively from severely contaminated food than other current enrichment media.

Colony Count, Microbial↗
PubMed1989

Listeria monocytogenes in foods. Isolation, characterization and control.

The intent for examining foods for Listeria monocytogenes, i.e. for surveying, for epidemiological purposes, or to inspect consignments of foods for microbiological safety, determines which analytical method is to be used. For instance resuscitation of debilitated cells may be required, and the degree of accuracy and precision necessary should be considered. Moreover, in the case of acceptance-or-rejection monitoring target values for 'absence' of the pathogen have been amply but not always effectively discussed. Recommendations are given for assessing adequate repair of sublethally damaged populations of L. monocytogenes and for performance testing of selective enrichment and isolation media to be used for the isolation and enumeration of L. monocytogenes. An approach to the empirical assessment of reference values for L. monocytogenes in foods processed for safety is also presented. This relies on a data base of results obtained when examining foods manufactured and distributed according to practices previously validated by longitudinally integrated ('holistic') quantitative risk analysis.

Culture Media↗
PubMed1989

Adequate protection of the public against food-transmitted diseases of microbial aetiology. Achievements and challenges, half a century after the introduction of the Prescott-Meyer-Wilson strategy of active intervention.

No dramatic change in the approach to supplying microbiologically safe foods and meals to the consumer occurred immediately upon the introduction, in the 1930's, by S.C. Prescott and K.F. Meyer in the U.S. and Sir Graham Wilson in the U.K. of the principle of taking preventive remedial measures rather than merely examining final product samples. Thus morbidity and the economic impact of food-borne disease of microbial aetiology continued to rise and new food-transmitted pathogens continued to be identified. The 1930 strategy was not implemented until 1970 when food processing specialists in the U.S. launched a similar approach under the new acronym 'HACCP' (hazard analysis: critical control points). This relies on (i) identification, by meticulous ecological studies, of hazardous practices and locations, termed 'critical points' by the new generation; (ii) elimination of such hazards by developing processing techniques designed to control contamination and colonization of foods--also given an innovative term, viz. GMP; (iii) validation of the elaborated procedures by a new stem to the Science of Public Health: risk assessment, perhaps better termed Safety Science; (iv) upon introduction of the validated GMP's monitoring limited numbers of samples--which have become fully representative because of process management--for ecologically valid marker organisms, indicating incidental going-out-of-control of manufacture or distribution. This implementation of the Prescott-Meyer-Wilson maxim has been given the name longitudinally integrated safety assurance, charmingly acronymized to LISA. Introduction of LISA eliminates all previously existing or perceived difficulties about microbiological target values ('standards') for foods. These can henceforth be empirically assessed from surveys on samples obtained from factories or catering establishments previously inspected for adherence to LISA, deficiencies having, where necessary, been rectified prior to the examination of samples. Unfortunately, a more general adoption of the LISA maxim in food technology occurred at almost the same time as people became concerned about the perceived negative health impact of processing food for safety. This culminated in widespread rejection of foods decontaminated by low dose gamma irradiation. While behaviourial scientists seriously attempt to identify the mechanisms of this anxiety and devise means of reassurance, food scientists should continue to elaborate innovative LISA procedures. In this context three promising areas of research and development are briefly discussed.

Animals↗
PubMed1988

A selective and diagnostic medium for use in the enumeration of Listeria spp. in foods.

A new medium, called RAPAMY agar, has been elaborated for the isolation from and the enumeration of Listeria spp. in foods. It is based on Ralovich's nalidixic acid-trypaflavin-agar with the following modifications: (i) the slight inhibitory properties of that medium were overcome by the use of Columbia Blood agar base instead of tryptose agar and the addition of 0.05% ferric ammonium citrate and 2.5% egg yolk emulsion; (ii) selectivity was improved by the addition of 0.25% 2-phenyl ethanol and incubation under microaerobic conditions; (iii) the medium was provided with two diagnostic traits by the addition of (a) aesculin + ferric ammonium citrate; and (b) D-mannitol and phenol red. The growth of Enterococcus spp., the only organisms other than Listeria spp. which grow on RAPAMY agar, was not inhibited by the addition of 20 microgram.ml-1 Cefoxitin (Moxolactam). Higher levels inhibited some Listeria spp., but not the enterococci. The medium recovered Listeria spp. quantitatively and allowed recovery from foods colonized by Enterococcus spp. at levels upto 10(2) per g.

Colony Count, Microbial↗
PubMed1988

Mould spoilage of cereals during transportation by sea from Latin America to Europe mechanisms, impact and management.

Safe water contents of consignments of cereals to be shipped overseas can be calculated from the relation between mould-free storage time and storage conditions (temperature of the environment, aw of the cereal), corrected for heterogeneity of water distribution, content of damaged kernels and degree of infestation by insects. The validity of this model was substantiated by the inspection of shipments and theoretical data from the literature. This predictive model can usefully be substituted for previously used, ill-defined criteria like average or any portion's water content and should prompt the trade to sell consignments of cereals on the basis of dry substance.

Edible Grain↗
PubMed1988

Bacteriological quality of broiler carcasses as affected by in-plant lactic acid decontamination.

In an attempt to improve the bacteriological quality of broiler carcasses the bactericidal effect of treatments with 1% and 2% lactic acid was investigated. Bacterial colonisation was determined immediately after treatment, after the carcasses had been chilled and during storage at 0 degrees C. Examination included numbers of mesophilic aerobic and psychrotrophic aerobic colony-forming units (CFU), CFU of Enterobacteriaceae at 37 degrees C and CFU of Staphylococcus aureus. Immediately after treatment colonisation per gram skin was generally reduced by about 1 log. Initially 2% lactic acid was not found significantly more effective in reducing colony counts than 1%. However, treatment with 2% lactic acid suppressed post-decontamination colonisation with Enterobacteriaceae more effectively than 1% lactic acid, as determined after 15-18 days storage at about 0 degrees C. Lactic acid treatment was most effective when applied shortly before chilling. Successive treatment at three different stages during slaughtering did not increase reduction of colony counts. It is concluded that decontamination with 1-2% lactic acid at pH 2, when applied shortly before chilling, will markedly improve the bacterial safety and increase the refrigerated shelf life of broiler carcasses.

Animals↗