June 27

Symposium: Food Microbiology

In collaboration with the University of Guelph a joint symposium about Food Microbiology was held on Friday the 27th of July. The symposium, attended by more than 70 people, was opened by Dr Griffiths of the University of Guelph (UofG). His department, the Canadian Research Institute for Food Safety (CRIFS) has a farm to fork approach and joints work with the department of Food Science chaired by Keith Warriner.
Next, Prof. Abee introduced the Wageningen University and Research centre (WUR). This university has 6 colleges, Agricultural technology and Food sciences, Plant sciences, Social sciences, Environmental sciences, and animal sciences. There are students from all over the world, more than 100 nationalities. The department of Food Microbiology, works both on Food quality & functionality and Food safety covered by the subjects: chain wide risk assessment, hygiene and detection, fermentation, and genomics & physiology. Last subject is the working field of Abee.
Véronique Delcenserie (UofG) studied the genomic difference between two Bifidobacterium longum strains: CRC-002 and NCC 2705 using the SSH method. Her conclusion is that the SSH method an efficient method is to compare two closely related genomes. Furthermore, the research demonstrates the presence of an interesting technological potential for CRC-002 strain: presence of EPS machinery and presence of endoxylanase.
Els Peters (WUR) validates the Gamma hypothesis of microbial growth. In the hurdle technology several inhibitory effects are combined. These effects can either be interactive, which results in a greater protection than expected, or with no interaction, which is called the Gamma hypothesis. Up to now, the Gamma hypothesis seems to describe the combination of pH and undissociated acid concentration . However, the data collection is not yet finished and the modelling will be extended.
Jianxiong Ye (UofG) used a combination of antagonistic bacteria and bacteriophage to control Salmonella on sprouted mung beans. She concluded that an Enterobacter strain exhibits antagonistic activity against Salmonella. The combination of Enterobacter and phages exhibit synergistic activity against Salmonella.
Maarten Mols (WUR) titled his presentation “What makes acid stress lethal? Exposure of Bacillus cereus to mild and lethal acid stress leads to response specific transcriptome profiles.” The strains investigated are ATCC 14579, an air isolate, and ATCC 10987, a cheese isolate. The conclusions were:pH 5.0 or lower inactivates B. cereus strain ATCC 10987, ATCC 14579 can continue growth at pH 5.0 or higher and is inactivated at pH 4.6 and lower. Main difference between transcriptomes from cells exposed to mild and lethal acid is in induction level. Induction of alternative electron transfer chain components (nitrate reductase) is main difference between the strains tested. Cytoplasmic acidification, perturbation of electron transfer chain and formation of oxidative compounds are indicators of acid-induced malfunctioning of cellular processes that may lead to cell death.
Angela Maria Tellez-Garay (UofG) presented her work about “Milk Fermented with L. helveticus protects mice against Salmonella infection”. The general objective was to confirm immunomodulatory effect of peptidic fraction(F5) from milk fermented by L. helveticus”. Her conclusions were:Mice fed with F5 (100 μl of 0.2 μg/ml) showed significant high health score index than control group. Percentage of surviving mice was significant higher for PO2-fed group compared with control group. Salmonella translocation in liver and spleen was lower in mice from PO2 group compared with the other groups tested. F5 showed to induce TNF-α production in early stage of infection. Mice with a low rate of bacterial clearance exhibited a Th1 cytokine pattern and higher IFN-γ production by T cells than mice with a high rate of clearance. Results suggest that the T cells involved in clearance act through mechanism different from IFN- γ production.
Naiyana Chaitiemwong (WUR) presented her work on the transmission of Listeria monocytogenes from/to cooked meat products via slicing machine. The transfer rate of L. monocytogenes from the ham to surface of the slicing machine is the highest on table, handle board, and plate. The transfer rate of L. monocytogenes from surface to ham decreased as the number of slices increased except for the last cut. The higher transfer rate on the last ham was because of a long contact and a large area exposed to the contaminated areas. After balancing the input and output it appeared that not all L. monocytogenes transferred to the slicing machine and clean ham. At higher concentration (106 cfu/cm2) transfer rate is higher than at low concentration (104 cfu/cm2).
Maira J. Medellin-Peña (UofG) investigated molecules secreted by probiotics. They are useful to prevent infection by harmful bacteria. Her conclusions are that probiotics secrete molecules that are involved in the QS regulation of virulence in EHEC O157:H7 and Salmonella Typhimurium. Furthermore, probiotics can be use as an alternative therapy to treat gastrointestinal infections.
Mark de Been (WUR) presented:”Identification of the transcriptional networks governed by two-component signal transduction systems in Bacillus cereus and closely related organisms.” The goal was to predict regulatory networks of B. cereus TCSs; which genes are controlled by which TCS and to understand adaptive flexibility of B. cereus and relatives. So far, this research gave useful information for phylogenetic footprinting and insight in the adaptive flexibility of B. cereus / Gram-positives.
Kim Hyung Jung (UofG) presented her work “Quantitative risk modeling for staphylococcal intoxication from meat-based food dishes prepared in food service establishments in Korea”. Her conclusions are that the simulation results (baseline model) show a very low probability for staphylococcal intoxication in food service establishments and do not reflect extremely bad practices. The scenario analysis showed that a slight change in initial variables increased the possibility of staphylococcal intoxication. This risk model can be used as platform risk model for staphylococcal intoxication in food service establishments. Furthermore, a new approach for staphylococcal intoxication is suggested: threshold model using minimum toxin dose, prediction of toxin production.
Pradeep Dahiya from PDQ group (WUR) introduced the project Telfun aiming to better understanding of the role of local food networks in food sovereignty and providing scientific support for improving crop-food combinations as means to enhance food sovereignty, and his research target Mung bean (Vigna radiata) yielded in India.
Asad Raza (UofG); he studied on the dissemination of enteric contamination in beef processing lines. By sponge samples from three anatomical locations of carcass and air samples collected from dehiding, evisceration and washing areas, the plate counts of indicator generic E.coli showed that farm/stun floors and transportation were the main cross-contamination points. The E.coli populations appeared to be diverse and heterogeneously distributed over carcasses by using ERIC-PCR DNA fingerprinting.
Ineke van Boeijen (WUR) switched to heterogeneity of Listeria monocytogenes population. From a strain LO28 population, 23 mutants with stable resistance to high hydrostatic pressure were further characterized for resistance to other stresses (heat, acid), growth and motility. This result will be clustered to obtain insight in the different mechanisms involved in piezotolerance, correlated with the further Microarray experiments.
Rocío Morales (UofG) tested a few non-conventional methods for separation or detection of food-borne pathogens were including Immunomagnetic separation (C. jejuni) and Ion exchange filtration - RT-PCR assay (murine Norovirus, MNV). The former could only be used as a qualitative method for the rapid detection of Campylobacter due to the low recovery of beads and necessary enrichment procedure. Up to 30% MNV can be recovered from ion exchange filters and the detection limit of latter method could be 101 PFU.
Petra Roubos (WUR) introduced her study about tempe, a traditional Indonesian soybean-fermented food. It has been concluded that tempe extracts can protect against the adhesion of enterotoxgenic E. coli to pig intestinal brush borders and Caco-2 epithelial cells and might protect pig as well human intestinal cells against E. coli infection. The putative functional fraction could be a specific carbohydrate.
Sandy Moorhead (UofG) was interestingly the only English-native speaker presenting today (Sandy comes from New Zealand). Her speech was about the physiological characteristics of an Autoinducer-2 mutant of C. jejuni. Autoinducers is defined as low molecular weight diffusible molecules synthesized by one organism to trigger gene activation in others, which process is called Quorum Sensing. Sandy´s results indicated that some survival and virulence characteristics are regulated by AI-2.
At 4:00 pm, the symposium was successfully completed and closed by Prof. Abee. Then a reception was held in University Club, UofG, in which all participants were invited. (Ida Dijkhoff-Jongenburger and Yinghua Xiao)