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Call number: LD2668 .T4 1950 L8 / Master of Science

Digitized by Kansas Correctional Industries

Bacillus cereus is the most prevalent pathogenic Bacillus species found in foods, causing food spoilage and two types of toxin-mediated food poisoning known as the diarrhoeal and emetic syndromes. Other Bacillus species, particularly B. subtilis, B. licheniformis, B. brevis, B. pumilus and B. thuringensis, have also been recognised as food poisoning bacteria of increasing concern, with reports of outbreaks of diarrhoeal or emetic food poisoning. This study involved a systematic ecological investigation of Bacillus species isolated from rice products, commonly associated with Bacillus emetic food poisoning, using cultural and molecular methods. A centrifugation-plating method, more sensitive than the conventional spread plating method, was developed and used to determine the occurrence and biodiversity of Bacillus species in rice, a well known source of B. cereus. Eight different Bacillus species, B. cereus/B. thuringiensis, B. mycoides, B. subtilis/B. mojavensis, B. licheniformis, B. pumilus, B. sphaericus/B. fusiformis and B. megaterium, as well as Paenibacillus species, identified by partial rDNA sequencing, were isolated from raw (uncooked) and cooked rice products. The diversity of the isolates at the subspecies (strain) level was investigated using the RAPD-PCR typing technique, which proved to be useful for differentiating strains of bacilli, revealing broad diversity among the strains. Generally, different genotypes were found in raw and cooked rice, with some isolates of the same RAPD pattern found in both raw and cooked rice. The toxigenic potential of Bacillus isolates were also determined by molecular and immunological analysis as well as an MEKC method, developed in this study for quantitative analysis of the emetic toxin, cereulide. The results revealed that most isolates from the B. cereus group were potentially or actually toxigenic and some isolates were able to produce both diarrhoeal and emetic toxins. Other Bacillus species outside the B. cereus group were also shown to produce cereulide.

Thesis (M.S.)--University of Wisconsin--Madison, 1984. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

The aim of this investigation was to evaluate the hygiene of domestic food preparation practices. The traditional survey approach used to study this behaviour has problems of interpretation and verification. In this study direct observation, supplemented with food temperature measurements was used to gather information for the purpose of developing an understanding of the causes of domestic food poisoning. The food handling practices of 108 people preparing foods commonly implicated in outbreaks of food poisoning were analysed. A HACCP approach was employed and a standard measure of hygienic food handling behaviour, the Food Safety Risk Score, (FSR) was devised. The FSR score indicated the extent of the use of appropriate control measures during food preparation. The higher the score the greater the risk of unsafe food being produced. Scores expressed as a percentage, ranged from 0 to 65% with over half of the subjects scoring below 20%. More than half (60%) of the people cooked in advance of consumption but most (85%) cooked the food thoroughly. Few used any method to speed the cooling of cooked food. Temperature abuse during food transport and storage was exhibited by more than 40% of people. Cooked food was held at ambient temperature for prolonged periods by 19% of the people and was re-heated inadequately by 11%. The standard of personal hygiene of some participants was low. An assessment of the cleanliness of the domestic kitchen and the condition of equipment and surfaces used in food preparation, based on ATP measurements and a kitchen checklist showed that there was a wide variation in the standards found in homes. The great potential for indirect and direct cross contamination in the domestic kitchen was highlighted. The problems involved in persuading people to practise well-known food hygiene principles are considered and recommendations for improving domestic food hygiene are made.

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