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Papers by Arjen Wagendorp

Antonie Van Leeuwenhoek International Journal of General and Molecular Microbiology, 2002

Spore-forming bacteria can survive food-processing treatments. In the dairy industry, Bacillus an... more Spore-forming bacteria can survive food-processing treatments. In the dairy industry, Bacillus and Clostridium species determine the shelf-life of a variety of heat-treated milk products, mainly if the level of post-process contamination is low. In order to minimize problems caused by bacterial spores in foods and food production processes a chain management approach, from raw materials, ingredients and environmental sources to

FEMS Microbiology Letters, 2006

International Journal of Dairy Technology

The performance of the ISO method for the 'Enumeration of the Specially Thermoresistant Spores of... more The performance of the ISO method for the 'Enumeration of the Specially Thermoresistant Spores of Thermophilic Bacteria in Dried Milk' (ISO/TS27265; 2009) was compared with a more practical method. Both were tested for predictability of spoilage of UHT treated reconstituted milk. The data show that heating for 30 min at 100°C has the same predictive value as heating for 30 min at 106°C, provided that specifications are increased 1 log 10 and the use of TSA as a cultivation medium is recommended over PCMA. Predictability of spoilage using classical plating methods is furthermore discussed in relation to variation in spore heat resistance of spores commonly present in the dairy industry.

Journal of food protection, 2009

Listeria monocytogenes is a foodborne pathogen that has the ability to survive relatively high te... more Listeria monocytogenes is a foodborne pathogen that has the ability to survive relatively high temperatures compared with other nonsporulating foodborne pathogens. This study was performed to determine whether L. monocytogenes strains with relatively high heat resistances are adequately inactivated in a high-temperature, short-time pasteurization process (72 degrees C for 15 s). To obtain heat-resistant strains, 48 strains were exposed to 55 degrees C for up to 3 h. The energy of activation constant and inactivation constant of strains that survived best (strains 1E and NV8) were subsequently determined in a continuous-flow-through system. Strain Scott A was taken along as a reference. The 3 strains were cultured in whole milk and in brain heart infusion broth at 30 and 7 degrees C. Strains 1E and NV8 were significantly more heat resistant than was strain Scott A after growth in brain heart infusion broth at 30 degrees C and after growth in milk at 7 degrees C. From the inactivation...

International Journal of Food Microbiology, 2015

In the current study, the outgrowth of spores of 15 different food isolates of Clostridium perfri... more In the current study, the outgrowth of spores of 15 different food isolates of Clostridium perfringens was evaluated in vacuum-packed ground beef during storage at 12°C and 25°C. This included enterotoxic strains carrying the gene encoding the CPE enterotoxin on the chromosome (C-cpe), on a plasmid (P-cpe) and cpe-negative strains. The 15 strains were selected from a larger group of strains that were first evaluated for their ability to sporulate in modified Duncan-Strong sporulating medium. Sporulation ability varied greatly between strains but was not associated with a particular cpe genotype. In line with previous studies, the tested C-cpe strains produced spores with significantly higher heat resistance than the cpe-negative and P-cpe strains (both IS1151 and IS1470-like) with the exception of strain VWA009. Following inoculation of vacuum-packed cooked ground beef with spores, the heat-resistant C-cpe strains showed lower outgrowth potential in this model food stored at 12°C than the P-cpe and cpe-negative strains, while no significant differences were observed at 25°C. These results suggest that the latter strains may have a competitive advantage over C-cpe strains at reduced temperatures during storage of foods that support the growth of C. perfringens. While spores of P-cpe strains are readily inactivated by heat processing, post-processing contamination by food handlers who may carry P-cpe strains that have a better growth potential at lower temperatures must be avoided. The varying responses of C. perfringens spores to heat and the differences in outgrowth capacity at different temperatures are factors to be considered in strain selection for challenge tests, and for predictive modelling of C. perfringens.

Journal of Pediatric Gastroenterology and Nutrition, 2000

An obvious difference between breast-fed and formula-fed newborn infants is the development of th... more An obvious difference between breast-fed and formula-fed newborn infants is the development of the intestinal flora, considered to be of importance for protection against harmful micro-organisms and for the maturation of the intestinal immune system. In this study, novel molecular identification methods were used to verify the data obtained by traditional culture methods and to validate the culture independent fluorescent in situ hybridization (FISH) technique. From each of six breast-fed and six formula-fed newborn infants, six fecal samples were obtained during the first 20 days of life. The microbial compositions of the samples were analyzed by culturing on specific media and by FISH, by using specific 16S rRNA-targeted oligonucleotide probes. The colonies growing on the media were identified by random amplified polymorphic DNA pattern analysis and by polymerase chain reaction amplification and subsequent analysis of the 16S rRNA gene. Molecular identification of the colonies showed that the selective media are insufficiently selective and unsuitable for quantitative analyses. Qualitative information from the culturing results combined with the data obtained by the FISH technique revealed initial colonization in all infants of a complex (adult-like) flora. After this initial colonization, a selection of bacterial strains began in all infants, in which Bifidobacterium strains played an important role. In all breast-fed infants, bifidobacteria become dominant, whereas in most formula-fed infants similar amounts of Bacteroides and bifidobacteria (approximately 40%) were found. The minor components of the fecal samples from breast-fed infants were mainly lactobacilli and streptococci; samples from formula-fed infants often contained staphylococci, Escherichia coli, and clostridia. This study confirms the differences in development of intestinal flora between breast-fed and formula-fed infants. The results obtained from the FISH technique were consistent. Although the repertoire of probes for this study was not yet complete, the FISH technique will probably become the method of reference for future studies designed to develop breast-fed-like intestinal flora in formula-fed infants.

International Dairy Journal, 1997

Isolates from UHT products suspected for the presence of highly heat resistant sporeforming bacte... more Isolates from UHT products suspected for the presence of highly heat resistant sporeforming bacteria obtained from different European countries and sporeforming bacteria isolated from heated raw milk were identified by 16s rRNA sequence analysis, RAPD-and REP-patterns. The isolates from the UHT products formed a very homogeneous group and based on the 16s rRNA sequence they belong to the recently described new species Bacillus sporothermodurans. Similar RAPD or REP-PCR patterns could be observed for all isolates from non-sterile UHT-milk, while other bacilli from milk had clearly different patterns. The heat resistance of the spores of B. sporothermodurans in the UHT region was high, less than three decimal reductions in 5 s at 140°C in particular compared to spores of other mesophilic sporeforrners and Bacillus stearothermophilus. Identification of B. sporothermodurans on phenotypic characteristics was problematic, partly because other Bacillus species with similar phenotypes could be isolated from raw milk. Since 16SrRNA sequence analysis for B. sporothermoduruns is complicated by the presence of multiple 16SrRNA types, it was concluded that for the rapid and reliable identification of isolates the application of RAPD or REP-PCR fingerprinting presents a most useful tool.

Applied and Environmental Microbiology, 2012

ABSTRACTOf 98 suspected food-borneClostridium perfringensisolates obtained from a nationwide surv... more ABSTRACTOf 98 suspected food-borneClostridium perfringensisolates obtained from a nationwide survey by the Food and Consumer Product Safety Authority in The Netherlands, 59 strains were identified asC. perfringenstype A. Using PCR-based techniques, thecpegene encoding enterotoxin was detected in eight isolates, showing a chromosomal location for seven isolates and a plasmid location for one isolate. Further characterization of these strains by using (GTG)5fingerprint repetitive sequence-based PCR analysis distinguishedC. perfringensfrom other sulfite-reducing clostridia but did not allow for differentiation between various types ofC. perfringensstrains. To characterize theC. perfringensstrains further, multilocus sequence typing (MLST) analysis was performed on eight housekeeping genes of both enterotoxic and non-cpeisolates, and the data were combined with a previous global survey covering strains associated with food poisoning, gas gangrene, and isolates from food or healthy indiv...

International Dairy Journal, 2006