Browsing by Author "Springael, Dirk"

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    Development and Validation of a Culture-Based Method Suitable for Monitoring Environmental Survival of Escherichia Coli O157:H7 and Salmonella Enterica Serovar Typhimurium in Developing Countries
    (Annals of microbiology, 2011) Ongeng, Duncan; Muyanja, Charles; Ryckeboer, Jaak; Geeraerd, Annemie Helena; Springael, Dirk
    A non-GMO culture-based method suitable for studying the fate of Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium in an agricultural environment in developing countries was developed and validated. This method is based on the use of spontaneous rifampicin-resistant mutants of non-toxigenic variants of E. coli O157:H7 and S. Typhimurium combined with counting of colony-forming units (CFU) on selective media, i.e., Cefixime–Tellurite–Sorbitol MacConkey agar containing 100 μg/ml rifampicin, 50 μg/ml cycloheximide and 50 μg/ml nystatin for E. coli O157:H7 and Xylose–Lysine–Tergitol-4 agar containing the same antimicrobials for S. Typhimurium. Validation experiments using gfp- and ds-red-labelled derivatives of the rifampicin-resistant mutants in a non-sterile manure-soil matrix demonstrated that the new culture method was effective in the selection and recovery of the test strains without any detectable interference from background contaminants both in the short and long term. The rifampicin-resistant-based culture method designed provides a feasible low-cost option to study environmental survival of E. coli O157:H7 and Salmonella spp. in developing countries.
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    Fate of Escherichia Coli O157:H7 and Salmonella Enterica in the Manure-Amended Soil-Plant Ecosystem of Fresh Vegetable Crops: A Review
    (Critical reviews in microbiology, 2015) Ongeng, Duncan; Geeraerd, Annemie Hellena; Springael, Dirk; Ryckeboer, Jaak; Muyanja, Charles; Mauriello, Gianluigi
    Enterohemorrhagic Escherichia coli (EHEC) and Salmonella enterica have been implicated in several disease outbreaks linked to consumption of fresh vegetables. Both ruminant and non-ruminant animals carry EHEC and S. enterica in their gastrointestinal tracts and can shed the pathogens in the faecal matter both in symptomatic and asymptomatic states. Application of animal waste in soil fertility management and irrigation of crops with contaminated waste water has been recognised as an important route through which EHEC and S. enterica can contaminate fresh vegetables during primary production. The behavior of E. coli O157:H7 and S. enterica in the agricultural environment has been extensively studied in the last decades. Several microbiological detection methods have been applied. This review therefore puts together current knowledge on the behavior of E. coli O157:H7 and S. enterica in the manure-amended soil-plant ecosystem of fresh vegetable crops during cultivation under various environmental conditions. The review focuses on methodological issues involved in undertaking survival studies and makes comparative analysis of experimental results obtained from studies conducted under controlled environmental conditions integrating results obtained from field experiments. Finally, a theoretical discussion on the potential likely impact of climate change on pre-harvest safety of field-cultivated vegetables is highlighted.
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    Modeling the Fate of Escherichia coli O157:H7 and Salmonella enterica in the Agricultural Environment: Current Perspective
    (Journal of food science, 2014) Ongeng, Duncan; Haberbeck, Leticia U.; Mauriello, Gianluigi; Ryckeboer, Jaak; Springael, Dirk; Geeraerd, Annemie H.
    The significance of fresh vegetable consumption on human nutrition and health is well recognized. Human infections with Escherichia coli O157:H7 and Salmonella enterica linked to fresh vegetable consumption have become a serious public health problem inflicting a heavy economic burden. The use of contaminated livestock wastes such as manure and manure slurry in crop production is believed to be one of the principal routes of fresh vegetable contamination with E. coli O157:H7 and S. enterica at preharvest stage because both ruminant and nonruminant livestock are known carriers of E. coli O157:H7 and S. enterica in the environment. A number of challenge-testing studies have examined the fate of E. coli O157:H7 and S. enterica in the agricultural environment with the view of designing strategies for controlling vegetable contamination preharvest. In this review, we examined the mathematical modeling approaches that have been used to study the behavior of E. coli O157:H7 and S. enterica in the manure, manure-amended soil, and in manure-amended soil–plant ecosystem during cultivation of fresh vegetable crops. We focused on how the models have been applied to fit survivor curves, predict survival, and assess the risk of vegetable contamination preharvest. The inadequacies of the current modeling approaches are discussed and suggestions for improvements to enhance the applicability of the models as decision tools to control E. coli O157:H7 and S. enterica contamination of fresh vegetables during primary production are presented.
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    Rhizosphere Effect on Survival of Escherichia Coli O157:H7 and Salmonella Enterica Serovar Typhimurium in Manure-Amended Soil during Cabbage (Brassica Oleracea) Cultivation under Tropical Field Conditions in Sub-Saharan Africa
    (International Journal of Food Microbiology, 2011) Ongeng, Duncan; Muyanja, Charles; Ryckeboer, Jaak; Geeraerd, Annemie H.; Springael, Dirk
    The effect of cabbage (Brassica oleracea) rhizosphere on survival of Escherichia coli O157:H7 and Salmonella Typhimurium in manure-amended soils under tropical field conditions was investigated in the Central Agro-Ecological Zone of Uganda. Three-week old cabbage seedlings were transplanted and cultivated for 120 days on manure-amended soil inoculated with 4 or 7 log CFU/g non-virulent E. coli O157:H7 and S. Typhimurium. Cabbage rhizosphere did not affect survival of the 4 log CFU/g inocula in manure-amended soil and the two enteric bacteria were not detected on/in cabbage leaves at harvest. The 7 log CFU/g E. coli O157:H7 and S. Typhimurium survived in bulk soil for a maximum of 80 and 96 days, respectively, but the organisms remained culturable in cabbage rhizosphere up to the time of harvest. At 7 log CFU/g inoculum, E. coli O157:H7 and S. Typhimurium contamination on cabbage leaves occurred throughout the cultivation period. Leaf surface sterilisation with 1% AgNO3 indicated that the organisms were present superficially and in protected locations on the leaves. These results demonstrate that under tropical field conditions, cabbage rhizosphere enhances the persistence of E. coli O157:H7 and S. Typhimurium in manure-amended soil at high inoculum density and is associated with long-term contamination of the leaves.