The contribution of microbial ecology to management and monitoring of the safety, quality and acceptability (SQA) of foods.
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Food↗
Biomedical subjects
D A Mossel
Publications and source records attributed to D A Mossel.
[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↗
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↗
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↗
[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↗
Staphylococcus aureus and related staphylococci in foods: ecology, proliferation, toxinogenesis, control and monitoring.
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Animals↗
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↗
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↗
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↗
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↗
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↗
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↗
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↗
[Identification and prevention of meat poisoning].
In this contribution to a series 'Papers of Yesterday and Today' a retrospective review of developments in the identification and control of meat 'poisoning' defined as infections and intoxications following the ingestion of bacteriologically unsound meat and meat products is presented. Starting from two classical Dutch papers, viz. by H. J. H. Stempel (1891) and K. Hoefnagel (1899) illustrating the knowledge of meat 'poisoning' acquired in the nineties of the 19th century, developments in the field of bacteriological research on meats and the resulting efforts to manage meat 'poisoning' are summarised. Attention is paid to the role of Dutch veterinarians in investigations on the aetiology of meat infections resulting in the adoption of legal meat inspection in 1922 and the ensuing reduction in the occurrence of mass outbreaks of meat poisoning. However, despite marked improvement of the standard of hygiene in the food industry in general and expert monitoring of meat production lines by veterinarians in particular, infections and intoxications transmitted by meat and meat products are still quite prevalent. Essentially, their management can only be achieved by strict adherence to Good Manufacturing Practices (GMP) throughout animal husbandry, slaughter, distribution and storage, termed longitudinally integrated safety assurance. Professional monitoring by an up-to-date meat inspection system, however, continues to be indispensable in the prevention of food-borne infections and intoxications. Some recommendations are made for effective intervention in the infection cycle of food-transmitted pathogens originating from the high infection pressure on slaughter lines, resulting from contamination acquired at previous stages of the animal production chain.
Animals↗
Integrated microbiological safety assurance and monitoring of food and drinking water. Professor Kampelmacher's contribution to postgraduate education in The Netherlands from the point of view of Veterinary Public Health.
The history of academic education in food microbiology and hygiene in the Netherlands has largely been written by Prof. Kampelmacher. The first contribution in this field dates from 1961, and suggested a new approach to teaching Veterinary Public Health. His later research led to the conclusion that intervention would be the only way to control the food-transmitted diseases originating from slaughter animals and poultry, particularly Salmonellosis. This intervention should take place at the beginning of the contamination cycle. In the 1970's, surveys showed that feed decontamination would no longer efficiently control the endemicity of Salmonellosis. The contamination cycles had become autonomous. Consequently, emphasis on terminal decontamination of food products was necessary. Besides his activities in teaching and research, Prof. Kampelmacher masterminded a modern view of the responsibilities of academic scientists. Moreover, he strongly promoted an interdisciplinary approach to scientific consultation and advice. In this respect, he has unfortunately not been successful in introducing radiation of dangerously contaminated food, having met strong opposition from various quarters. His efforts in multidisciplinary training and research programmes resulted in, among other things, fruitful cooperation between the Agricultural University at Wageningen and the Faculty of Veterinary Medicine at Utrecht University.
Education, Graduate↗
[A small outbreak of salmonellosis caused by Bologna sausage].
Late in August 1985, seventeen subjects in the 3-40 year range contracted salmonellosis which was associated with the consumption of fermented pork sausage prepared by a butcher. The incubation period varied from 6 to 9 hours, the attack rate was a hundred per cent; there were no deaths or complications. The pH of the incriminated sausage was 5.7 (the pH of controls ranged from 4.5 to 5.0), and the aw was 0.99 (vs. 0.92-0.97 in the controls), a colony count of thermotrophic Enterobacteriaceae was 10(7) per 1 g, including c. 10(6) of Salmonella typhimurium, c. 10(3) Staphylococcus aureus and c. 10(4) cfu of Clostridium perfringes per 1 g. These outbreaks may be prevented by ensuring good practices during production and distribution, supported by monitoring line samples by determining the pH and aw and cfu assessment of Staphylococcus aureus and thermotrophic Enterobacteriaceae.
Adolescent↗
The enumeration of thermotrophic types amongst the Enterobacteriaceae colonizing perishable foods.
A total of 41 pure cultures of Enterobacteriaceae, comprising 32 thermotrophic and nine psychrotrophic strains, pathogens or marker organisms, were examined for numbers of colony forming units obtained at 37 degrees and 42.5 degrees C (thermotrophs) and 30 degrees C (psychrotrophs), when surface-plated on a rich infusion agar and violet red bile agar. In addition 42 food and water samples, collected in a rural area of the Philippines, were examined by surface inoculating violet red bile AIPC (agar immersion plating and contact; 'dip') slides and incubating at 37 degrees and 42.5 degrees C. At 42.5 degrees C there was almost total recovery of the thermotrophic Enterobacteriaceae, whereas the psychrotrophic strains were completely suppressed. At 37 degrees C the psychrotrophs were only slightly inhibited. The Philippine foods, predominantly cooked meals, milk and drinking water, appeared to be significantly colonized by thermotrophic Enterobacteriaceae. It is concluded that incubation at 42.5 degrees C satisfactorily selects enteropathogenic and other enteric Enterobacteriaceae while suppressing the psychrotrophic types which are mainly of vegetable origin. It is emphasized that, regardless of the temperature used, a resuscitation procedure for Enterobacteriaceae populations that have incurred sublethal injury in food has to precede counts on or in the usual selective media.
Animals↗
Microbiological markers for swimming-associated infectious health hazards.
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Humans↗