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Diversity and Occurrence of Free-Living Protozoa on Food and in Food-Related Environments

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Diversity and Occurrence of Free-Living Protozoa on Food and in Food-Related Environments Diversity and occurrence of free-living protozoa on food and in food-related environments Natascha Chavatte Dissertation submitted in fulfilment of the requirements for the degree of Doctor in Veterinary Sciences (PhD) 2016 Promotors: Prof. Dr. Kurt Houf Department of Veterinary Public Health and Food Safety Faculty of Veterinary Medicine Ghent University Prof. Dr. Koen Sabbe Department of Biology Faculty of Sciences Ghent University Members of the examination committee Chairman Prof. Dr. Annemie Decostere Dr. Julie Baré Prof. Dr. Edwin Claerebout Dr. Lieve Herman Prof. Dr. Ir. Mieke Uyttendaele Dr. Jeroen Van Wichelen Prof. Dr. Anne Willems To cite this thesis Chavatte N. (2016). Diversity and occurrence of free-living protozoa on food and in food-related environments. Thesis submitted in fulfilment of the requirements for the degree of Doctor in Veterinary Sciences (PhD), Faculty of Veterinary Medicine, Ghent University. The author and promoters give the permission to consult and to copy parts of this work for personal use only. Any other use is subject to the Laws of Copyright. Permission to reproduce any material contained in this work should be obtained from the author. Table of contents Table of contents Table of contents.......................................................................................................................................................5 List of abbreviations ................................................................................................................................................ 13 Preface .................................................................................................................................................................... 21 General introduction ............................................................................................................................................... 25 1 Free-living protozoa ......................................................................................................................................... 27 1.1 Morphology .................................................................................................................................................... 27 1.2 Motility and feeding ....................................................................................................................................... 29 1.3 Life cycle and reproduction ............................................................................................................................. 31 1.4 Classification and phylogenetic relationships ................................................................................................. 31 1.5 Diversity .......................................................................................................................................................... 35 1.6 Ecology ........................................................................................................................................................... 37 2 Methodology ................................................................................................................................................... 43 2.1 Recovery and cultivation ................................................................................................................................ 43 2.2 Identification and quantification .................................................................................................................... 45 3 Impact of free-living protozoa on food safety and public health ...................................................................... 49 3.1 Free-living protozoa in food-related environments ........................................................................................ 49 3.2 Free-living protozoa on food products and in drinking water ........................................................................ 51 3.3 Free-living protozoa in animals and humans .................................................................................................. 53 3.4 Free-living protozoa in biofilms in the food environment ............................................................................... 55 3.5 Pathogenic and opportunistic free-living protozoa ........................................................................................ 57 3.6 Interactions of free-living protozoa with foodborne pathogenic bacteria ..................................................... 59 Scientific aims ......................................................................................................................................................... 69 Chapter 1. Co-occurrence of free-living protozoa and foodborne pathogens on dishcloths: implications for food safety ...................................................................................................................................................................... 73 Abstract ................................................................................................................................................................... 75 5 Table of contents 1 Introduction ..................................................................................................................................................... 77 2 Material and methods ..................................................................................................................................... 79 2.1 Development and evaluation of two protocols for the recovery and quantification of FLP from dishcloths . 79 2.1.1 Cultivation of FLP .................................................................................................................................... 79 2.1.2 Evaluation of the protocols .................................................................................................................... 79 2.2 Occurrence, enumeration and diversity of FLP on used dishcloths ................................................................. 81 2.3 Bacteriological analysis of used dishcloths ..................................................................................................... 83 2.4 Data analysis .................................................................................................................................................. 85 3 Results ............................................................................................................................................................. 87 3.1 Development and evaluation of two protocols for the recovery and quantification of FLP from dishcloths . 87 3.2 Occurrence, enumeration and diversity of FLP on used dishcloths ................................................................. 89 3.3 Bacteriological analysis of used dishcloths ..................................................................................................... 91 3.4 Evaluation of dishcloth usage and kitchen practices ...................................................................................... 91 4 Discussion ........................................................................................................................................................ 93 Acknowledgements ................................................................................................................................................. 99 Chapter 2. Abundance, diversity and community composition of free-living protozoa on vegetable sprouts ........ 107 Abstract ................................................................................................................................................................. 109 1 Introduction ................................................................................................................................................... 111 2 Material and methods ................................................................................................................................... 113 2.1 Occurrence, abundance and diversity of FLP ................................................................................................ 113 2.2 Total aerobic bacteria and Escherichia coli .................................................................................................. 115 2.3 Data analysis ................................................................................................................................................ 115 3 Results ........................................................................................................................................................... 117 3.1 Occurrence and abundance of FLP ............................................................................................................... 117 3.1.1 Within-lot variation .............................................................................................................................. 117 3.1.2 Between-lot variation ........................................................................................................................... 119 3.2 Diversity of free-living protozoa ................................................................................................................... 119 3.3 Bacterial load on vegetable sprouts ............................................................................................................. 125 7 Table of contents 4 Discussion .....................................................................................................................................................
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