R. Temmerman | Ghent University (original) (raw)

Papers by R. Temmerman

International Journal of Food Microbiology, 2005

A total of 58 probiotic products obtained worldwide, which were claimed to contain Bifidobacteriu... more A total of 58 probiotic products obtained worldwide, which were claimed to contain Bifidobacterium strains (including 22 yoghurts, 5 dairy fruit drinks, 28 food supplements and 3 pharmaceutical preparations) were investigated in parallel using a culture-dependent and a culture-independent approach. Three isolation media previously reported as selective for Bifidobacterium were evaluated for their suitability in the quality analysis of these products. Subsequently, possible bifidobacterial colonies were picked from the best medium and identified by means of rep-PCR fingerprinting using the BOX primer (BOX-PCR). Bifidobacterium animalis subsp. lactis, formerly classified as Bifidobacterium lactis, was most frequently found, but strains belonging to Bifidobacterium longum biotypes longum and infantis, Bifidobacterium bifidum and Bifidobacterium breve were recovered also. In parallel, all products were also subjected to culture-independent analysis which involved a nested-PCR step on total bacterial DNA extracted directly from the product, followed by separation of the amplicons by Denaturing Gradient Gel Electrophoresis (DGGE) and subsequent identification of species from the band patterns. By conventional cultivation, 70.7% of the products analysed were found to contain culturable bifidobacteria whereas by cultureindependent DGGE analysis members of the genus Bifidobacterium could be detected in 96.5% of the analysed products. Genotypic characterization of a number of bifidobacterial isolates at the strain level by means of Pulsed-Field Gel Electrophoresis (PFGE) revealed a relatively high degree of genomic homogeneity among the Bifidobacterium strains currently used in the probiotic industry. D

Engineering in Life Sciences, 2007

... [24] N. Raddadi, A. Cherif, D. Mora, H. Ouzari, A. Boudabous, F. Molinari et al., The autolyt... more ... [24] N. Raddadi, A. Cherif, D. Mora, H. Ouzari, A. Boudabous, F. Molinari et al., The autolytic phenotype of Bacillus thurin-giensis, J. Appl. ... [25] N. Raddadi, A. Cherif, D. Mora, L. Brusetti, S. Borin, A. Bou-dabous et al., The autolytic phenotype of the Bacillus cereus group, J. Appl. ...

Applied and Environmental Microbiology, 2003

In order to obtain functional and safe probiotic products for human consumption, fast and reliabl... more In order to obtain functional and safe probiotic products for human consumption, fast and reliable quality control of these products is crucial. Currently, analysis of most probiotics is still based on culture-dependent methods involving the use of specific isolation media and identification of a limited number of isolates, which makes this approach relatively insensitive, laborious, and time-consuming. In this study, a collection of 10 probiotic products, including four dairy products, one fruit drink, and five freeze-dried products, were subjected to microbial analysis by using a culture-independent approach, and the results were compared with the results of a conventional culture-dependent analysis. The culture-independent approach involved extraction of total bacterial DNA directly from the product, PCR amplification of the V3 region of the 16S ribosomal DNA, and separation of the amplicons on a denaturing gradient gel. Digital capturing and processing of denaturing gradient gel electrophoresis (DGGE) band patterns allowed direct identification of the amplicons at the species level. This whole culture-independent approach can be performed in less than 30 h. Compared with culturedependent analysis, the DGGE approach was found to have a much higher sensitivity for detection of microbial strains in probiotic products in a fast, reliable, and reproducible manner. Unfortunately, as reported in previous studies in which the culture-dependent approach was used, a rather high percentage of probiotic products suffered from incorrect labeling and yielded low bacterial counts, which may decrease their probiotic potential.

Applied and Environmental Microbiology, 2006

This study examined whether Legionella pneumophila is able to thrive on heat-killed microbial cel... more This study examined whether Legionella pneumophila is able to thrive on heat-killed microbial cells (necrotrophy) present in biofilms or heat-treated water systems. Quantification by means of plate counting, real-time PCR, and flow cytometry demonstrated necrotrophic growth of L. pneumophila in water after 96 h, when at least 100 dead cells are available to one L. pneumophila cell. Compared to the starting concentration of L. pneumophila, the maximum observed necrotrophic growth was 1.89 log units for real-time PCR and 1.49 log units for plate counting. The average growth was 1.57 ؎ 0.32 log units (n ‫؍‬ 5) for real-time PCR and 1.14 ؎ 0.35 log units (n ‫؍‬ 5) for plate counting. Viability staining and flow cytometry showed that the fraction of living cells in the L. pneumophila population rose from the initial 54% to 82% after 96 h. Growth was measured on heat-killed Pseudomonas putida, Escherichia coli, Acanthamoeba castellanii, Saccharomyces boulardii, and a biofilm sample. Gram-positive organisms did not result in significant growth of L. pneumophila, probably due to their robust cell wall structure. Although necrotrophy showed lower growth yields compared to replication within protozoan hosts, these findings indicate that it may be of major importance in the environmental persistence of L. pneumophila. Techniques aimed at the elimination of protozoa or biofilm from water systems will not necessarily result in a subsequent removal of L. pneumophila unless the formation of dead microbial cells is minimized.

International Journal of Food Microbiology, 2003

In the present study, a total of 55 European probiotic products were evaluated with regard to the... more In the present study, a total of 55 European probiotic products were evaluated with regard to the identity and the antibiotic resistance of the bacterial isolates recovered from these products. Bacterial isolation from 30 dried food supplements and 25 dairy products, yielded a total of 268 bacterial isolates selected from several selective media. Counts of food supplements showed bacterial recovery in 19 (63%) of the dried food supplements ranging from 10 3 to 10 6 CFU/g, whereas all dairy products yielded growth in the range of 10 5 -10 9 CFU/ml. After identification of the isolates using whole-cell protein profiling, mislabeling was noted in 47% of the food supplements and 40% of the dairy products. In six food supplements, Enterococcus faecium was isolated whereas only two of those products claim this species on their label. Using the disc diffusion method, antibiotic resistance among 187 isolates was detected against kanamycin (79% of the isolates), vancomycin (65%), tetracycline (26%), penicillinG (23%), erythromycin (16%) and chloramphenicol (11%). Overall, 68.4% of the isolates showed resistance against multiple antibiotics including intrinsic resistances. Initially, 38% of the isolated enterococci was classified as vancomycin resistant using the disc diffusion method, whereas additional broth dilution and PCR assays clearly showed that all E. faecium isolates were in fact vancomycin susceptible. D

International Journal of Food Microbiology, 2005

A total of 58 probiotic products obtained worldwide, which were claimed to contain Bifidobacteriu... more A total of 58 probiotic products obtained worldwide, which were claimed to contain Bifidobacterium strains (including 22 yoghurts, 5 dairy fruit drinks, 28 food supplements and 3 pharmaceutical preparations) were investigated in parallel using a culture-dependent and a culture-independent approach. Three isolation media previously reported as selective for Bifidobacterium were evaluated for their suitability in the quality analysis of these products. Subsequently, possible bifidobacterial colonies were picked from the best medium and identified by means of rep-PCR fingerprinting using the BOX primer (BOX-PCR). Bifidobacterium animalis subsp. lactis, formerly classified as Bifidobacterium lactis, was most frequently found, but strains belonging to Bifidobacterium longum biotypes longum and infantis, Bifidobacterium bifidum and Bifidobacterium breve were recovered also. In parallel, all products were also subjected to culture-independent analysis which involved a nested-PCR step on total bacterial DNA extracted directly from the product, followed by separation of the amplicons by Denaturing Gradient Gel Electrophoresis (DGGE) and subsequent identification of species from the band patterns. By conventional cultivation, 70.7% of the products analysed were found to contain culturable bifidobacteria whereas by cultureindependent DGGE analysis members of the genus Bifidobacterium could be detected in 96.5% of the analysed products. Genotypic characterization of a number of bifidobacterial isolates at the strain level by means of Pulsed-Field Gel Electrophoresis (PFGE) revealed a relatively high degree of genomic homogeneity among the Bifidobacterium strains currently used in the probiotic industry. D

Engineering in Life Sciences, 2007

... [24] N. Raddadi, A. Cherif, D. Mora, H. Ouzari, A. Boudabous, F. Molinari et al., The autolyt... more ... [24] N. Raddadi, A. Cherif, D. Mora, H. Ouzari, A. Boudabous, F. Molinari et al., The autolytic phenotype of Bacillus thurin-giensis, J. Appl. ... [25] N. Raddadi, A. Cherif, D. Mora, L. Brusetti, S. Borin, A. Bou-dabous et al., The autolytic phenotype of the Bacillus cereus group, J. Appl. ...

Applied and Environmental Microbiology, 2003

In order to obtain functional and safe probiotic products for human consumption, fast and reliabl... more In order to obtain functional and safe probiotic products for human consumption, fast and reliable quality control of these products is crucial. Currently, analysis of most probiotics is still based on culture-dependent methods involving the use of specific isolation media and identification of a limited number of isolates, which makes this approach relatively insensitive, laborious, and time-consuming. In this study, a collection of 10 probiotic products, including four dairy products, one fruit drink, and five freeze-dried products, were subjected to microbial analysis by using a culture-independent approach, and the results were compared with the results of a conventional culture-dependent analysis. The culture-independent approach involved extraction of total bacterial DNA directly from the product, PCR amplification of the V3 region of the 16S ribosomal DNA, and separation of the amplicons on a denaturing gradient gel. Digital capturing and processing of denaturing gradient gel electrophoresis (DGGE) band patterns allowed direct identification of the amplicons at the species level. This whole culture-independent approach can be performed in less than 30 h. Compared with culturedependent analysis, the DGGE approach was found to have a much higher sensitivity for detection of microbial strains in probiotic products in a fast, reliable, and reproducible manner. Unfortunately, as reported in previous studies in which the culture-dependent approach was used, a rather high percentage of probiotic products suffered from incorrect labeling and yielded low bacterial counts, which may decrease their probiotic potential.

Applied and Environmental Microbiology, 2006

This study examined whether Legionella pneumophila is able to thrive on heat-killed microbial cel... more This study examined whether Legionella pneumophila is able to thrive on heat-killed microbial cells (necrotrophy) present in biofilms or heat-treated water systems. Quantification by means of plate counting, real-time PCR, and flow cytometry demonstrated necrotrophic growth of L. pneumophila in water after 96 h, when at least 100 dead cells are available to one L. pneumophila cell. Compared to the starting concentration of L. pneumophila, the maximum observed necrotrophic growth was 1.89 log units for real-time PCR and 1.49 log units for plate counting. The average growth was 1.57 ؎ 0.32 log units (n ‫؍‬ 5) for real-time PCR and 1.14 ؎ 0.35 log units (n ‫؍‬ 5) for plate counting. Viability staining and flow cytometry showed that the fraction of living cells in the L. pneumophila population rose from the initial 54% to 82% after 96 h. Growth was measured on heat-killed Pseudomonas putida, Escherichia coli, Acanthamoeba castellanii, Saccharomyces boulardii, and a biofilm sample. Gram-positive organisms did not result in significant growth of L. pneumophila, probably due to their robust cell wall structure. Although necrotrophy showed lower growth yields compared to replication within protozoan hosts, these findings indicate that it may be of major importance in the environmental persistence of L. pneumophila. Techniques aimed at the elimination of protozoa or biofilm from water systems will not necessarily result in a subsequent removal of L. pneumophila unless the formation of dead microbial cells is minimized.

International Journal of Food Microbiology, 2003

In the present study, a total of 55 European probiotic products were evaluated with regard to the... more In the present study, a total of 55 European probiotic products were evaluated with regard to the identity and the antibiotic resistance of the bacterial isolates recovered from these products. Bacterial isolation from 30 dried food supplements and 25 dairy products, yielded a total of 268 bacterial isolates selected from several selective media. Counts of food supplements showed bacterial recovery in 19 (63%) of the dried food supplements ranging from 10 3 to 10 6 CFU/g, whereas all dairy products yielded growth in the range of 10 5 -10 9 CFU/ml. After identification of the isolates using whole-cell protein profiling, mislabeling was noted in 47% of the food supplements and 40% of the dairy products. In six food supplements, Enterococcus faecium was isolated whereas only two of those products claim this species on their label. Using the disc diffusion method, antibiotic resistance among 187 isolates was detected against kanamycin (79% of the isolates), vancomycin (65%), tetracycline (26%), penicillinG (23%), erythromycin (16%) and chloramphenicol (11%). Overall, 68.4% of the isolates showed resistance against multiple antibiotics including intrinsic resistances. Initially, 38% of the isolated enterococci was classified as vancomycin resistant using the disc diffusion method, whereas additional broth dilution and PCR assays clearly showed that all E. faecium isolates were in fact vancomycin susceptible. D