Isolation, identification and characterization of Bacillus cereus from the dairy environment

In this thesis the occurrence of Bacillus cereus in the milk production and processing environment was investigated. Isolates were identified biochemically and by DNA probes based on the variable regions of 16S rRNA. Further characterization was carried out using biochemical and molecular typing, in order to determine the major contamination sources of milk. Furthermore, properties in relation to carbohydrate utilization, growth at low temperatures and enterotoxin production were examined.B. cereus is important as food spoilage organism. In the present study the microorganism was isolated from food ingredients such as yeast, flour, cacoa, herbs and spices. B. cereus was also found in a wide variety of processed food products including bakery products, Chinese meals, pasta products, chocolate and meat products. In pasteurized milk and dairy products, B. cereus was frequently present and it is well-known that it can be responsible for spoilage when post-heat- treatment contamination is absent.To enumerate spores in a sample, the most common procedure is to carry out a heat- activation treatment of 10 min at 80°C, followed by plating on a (selective) agar medium. To prevent germination of spores during sample preparation the time between the preparation of the primary dilution and heat-activation step should be less than 10 min and the temperature during the analysis should be as low as possible (e.g. by keeping dilutions in melting ice). After isolation, presumptive B. cereus are confirmed by biochemical tests, however, this may lead to incorrect identification. Several isolates, involved in food poisoning incidents, were shown to be B. thuringiensis, by sequencing part of the 16S rRNA. These results suggest that use of B. thuringiensis as insecticide may lead to foodborne infection or intoxication. To improve the confirmation procedure, we developed a specific and sensitive method, using DNA probes based on variable regions of the 16S rRNA, to differentiate between B. cereus and B. thuringiensis.On farms, B. cereus is introduced into raw milk by contamination of the udder with faeces, soil and, in winter, used bedding. In the dairy processing plants, additional contamination takes place via the equipment. Biochemical and growth characterization and molecular typing of isolates confirmed this and also showed that selection of strains occurs in the milk production and processing chain. Cleaning and disinfection will not eliminate all B. cereus in milking installations or heat exchangers, particularly not those adhering to surfaces of the equipment.Although only a few cases of milkborne infection and intoxication by B. cereus have been reported, most isolates were able to produce enterotoxin as determined by immunoblotting, cytotoxicity tests and PCR. However, if pasteurized milk is stored at7°C and consumed within the "best before" date, this will not cause any problems for healthy adults

Medicine, Medea and the Media: The Rise and Fall of Roy Meadow

For more than three decades eminent British paediatrician, Professor Sir Roy Meadow, was courted by the media for his startling pronouncements on maternal child murder and abuse, including his now infamous Meadow's Law and his creation ofMunchausen Syndrome by Proxy. His compelling evidence made headline news in the trials of several women, including Sally Clark, Donna Anthony, Angela Cannings and Trupti Patel. Journalists, however, persistently failed to investigate Meadow's potent claims, using the eminent paediatrician as a primary source to create highly newsworthy news narratives. Through an analysis of newspaper stories, primarily in the London Times, this study maps the rise and fall of Roy Meadow. My critique deploys a narrative trope I have called the Medea-Factor to explore the fictive qualities of news, and to develop an argument for understanding how Roy Meadow became the media's national authority on maternal child murder and abuse, as well as how his glittering career came to an ignominious end. An important key to revealing Meadow's power-and why it was that journalists continued to privilege his voice for so long--came in the unearthing of Meadow's nineteenth-century counterpart, and the first primary definer of infanticide news, Dr Edwin Lankester. This study concludes that the pattern for creating news narratives about mothers accused of murdering their children is so compelling that journalists, even when faced with the evidence of flawed science, will continue to create narratives shaped by the ideology ofthe Medea-Factor. The thesis is situated within the discipline of English, and its approach and methodology belong to that discipline. Its textual sources, however, come from newspapers, and to the extent that it is concerned with the use of expert witnesses the thesis engages with matters important to the discipline of journalism and is therefore interdisciplinary

Modelling Contamination of Raw Milk with Butyric Acid Bacteria Spores

Raw milk contains low concentrations of bacterial endospores, originating from the farm environment (e.g. soil, feeds, faeces). Spores of Clostridium tyrobutyricum, also called butyric acid bacterium (BAB), are of great interest to the dairy industry. They survive milk pasteurisation and cause off-flavours and texture defects in various cheese types. The contamination pathway of BAB spores is well known. Their primary origin is soil. In silage the number of spores will increase if conditions permit BAB growth. The spores are excreted in the cows faeces and are transferred to milk by contaminated teat surfaces. Many factors are involved in the contamination of milk with BAB spores. In this study, the contamination pathway was described using a combination of predictive models. The objective of the study was to quantitatively assess the importance of the different steps of the contamination pathway and to identify the most effective control points

Predictive Modelling Of Temperature And Water Activity (Solutes) On The In Vitro Radial Growth Of Botrytis Cinerea Pers

peer reviewe

Chlorate and Other Oxychlorine Contaminants Within the Dairy Supply Chain

The presence of chlorate in milk and dairy products can arise from the use of chlorinated water and chlorinated detergents for cleaning and sanitation of process equipment at both farm and food processor level. Chlorate and other oxychlorine species have been associated with inhibition of iodine uptake in humans and the formation of methemoglobin, with infants and young children being a high‐risk demographic. This comprehensive review of chlorate and chlorine derivatives in dairy, highlights areas of concern relative to the origin and/or introduction of chlorate within the dairy supply chain. This review also discusses the associated health concerns, regulations, and chemical behavior of chlorate and chlorine‐derived by‐products, and provides a summary of mechanisms for their detection and removal