Yersinia enterocolitica prevalence, on fresh pork, poultry and beef meat at retail level, in France

Y. enterocolitica is a zoonotic agent, and the third bacterial cause of human entiritis in Europe. The objective of this study was to assess consumer exposure to the pathogen Y. enterocolitica through meat consumption over a one-year period, in France. In this context, the prevalence of Y. enterocolitica was established on samples of fresh pork, beef and poultry collected at retail level in France. Of the 649 samples, 5.1% (34) were positive for Y. enterocolitica. No significant difference in prevalence between the categories of fresh meat was observed: the prevalence was 5.2 % for pork, 5.2% for beef and 5.9% for poultry meat. However, tongues of pork were highly contaminated by Y. enterocolitica (12.5%) compared to other type of meat

Chromosome Structuring Limits Genome Plasticity in Escherichia coli

Chromosome organizations of related bacterial genera are well conserved despite a very long divergence period. We have assessed the forces limiting bacterial genome plasticity in Escherichia coli by measuring the respective effect of altering different parameters, including DNA replication, compositional skew of replichores, coordination of gene expression with DNA replication, replication-associated gene dosage, and chromosome organization into macrodomains. Chromosomes were rearranged by large inversions. Changes in the compositional skew of replichores, in the coordination of gene expression with DNA replication or in the replication-associated gene dosage have only a moderate effect on cell physiology because large rearrangements inverting the orientation of several hundred genes inside a replichore are only slightly detrimental. By contrast, changing the balance between the two replication arms has a more drastic effect, and the recombinational rescue of replication forks is required for cell viability when one of the chromosome arms is less than half than the other one. Macrodomain organization also appears to be a major factor restricting chromosome plasticity, and two types of inverted configurations severely affect the cell cycle. First, the disruption of the Ter macrodomain with replication forks merging far from the normal replichore junction provoked chromosome segregation defects. The second major problematic configurations resulted from inversions between Ori and Right macrodomains, which perturb nucleoid distribution and early steps of cytokinesis. Consequences for the control of the bacterial cell cycle and for the evolution of bacterial chromosome configuration are discussed

Diversity of Yersinia enterocolitica population in a slaughterhouse between 2009 and 2010 and discrimination ability of MLVA compared to PFGE

Yersiniosis is a human disease mainly due to the ingestion of raw or undercooked pork meat contaminated mostly with Yersinia enterocolitica (Ye). In France, 74.3% of pig batches at slaughterhouses carried pathogenic Ye. Among them, biotype 4 (BT4) and biotype 3 (BT3) were often recovered. PFGE is one of the most used methods to type Ye, with the restriction enzymes, XbaI and NotI. Nevertheless, MLVA method based on the diversity of six loci tends to replace PFGE; this method showed a higher discriminatory power in others studies. We investigated the genetic diversity of Ye strains isolated in 2009 and in 2010 in one pig slaughterhouse in France and compared the ability of MLVA and PFGE to discriminate the strains. During these two years, 335 isolates were collected from pigs. The BT4 represented 88.4% of the strains (296/335) and the BT3 only 11.6% (39/335). PFGE using XbaI enzyme allowed the identification of 12 XbaI-PFGE types and among them only one was common to the both surveys. Because the Simpson’s Index shows a low genetic diversity 31 BT4 strains and 39 BT3 strains were typed using MLVA. For BT3 strains, MLVA had the same index of diversity than PFGE (DI=0.472). In contrary, the index of diversity was significantly higher with MLVA (DI=0.871) than with PFGE (DI=0.665) for BT4 strains. Our study revealed that the population of Ye in pig varied over the time. The comparison of the both typing methods indicated that MLVA has a better discriminatory power than XbaI-PFGE method for BT4 strains but not for BT3 strains

In vitro characterization of the ability of Yersinia enterocolitica BT4 to colonize pigs and stainless steel surfaces

Yersiniosis is, after campylobacteriosis and salmonellosis, the third most frequently reported zoonosis in Europe. Humans become infected with Y. enterocolitica through the consumption of undercooked pork and raw food having been in contact with contaminated surfaces. Pigs, the main reservoir for human pathogenic strains, do not develop clinical signs. In France and worldwide, biotype 4 (BT4) is the biotype the most frequently isolated from both pigs and clinical yersiniosis. In this study, a collection of 26 pathogenic BT4 strains isolated from pig tonsils was used to investigate their ability to adhere and invade intestinal pig cells (IPEC-J2) and to adhere to abiotic surfaces (stainless steel coupons) using two in vitro tests. Regression analysis was performed between data sets obtained from IPECJ2 cells assays versus stainless steel assays. All BT4 strains were able to adhere and invade IPEC-J2 cells. However, the results showed heterogeneity between strains with respect to their ability to adhere to IPECJ2 cells, with a percentage of adhesion varying from 9% to more than 90%. The BT4 population displayed a more homogeneous ability to invade IPECJ2 cells with percentages varying from 10% to 26%. The BT4 strains displayed a great ability to adhere to the stainless steel surface, percentage of adhesion varying from 0.3% to 4.2%. No correlation was observed between IPEC-J2 cell adhesion, cell invasion and adhesion to the stainless steel surface (R² \u3c 0.02). In conclusion, these results reflect the ability of the different BT4 strains to colonize the intestinal tract of pigs and to contaminate the stainless steel surfaces of the food processing environment

Etude de la conformation du chromosome chez la bactérie escherichia coli (plasticité et contraintes)

La connaissance des paramètres contraignant l'organisation des chromosomes est importante pour la compréhension plus générale du fonctionnement de la cellule. La plupart des génomes bactériens sont circulaires. Leur réplication progresse de façon bidirectionnelle à partir d'une origine unique et se termine dans la région opposée. La conformation chromosomique naturelle a été modifiée par des inversions. L'impact de ces réarrangements sur la physiologie de la cellule a été regardé. Les résultats montrent que le positionnement préférentiel des gènes sur le brin direct, la localisation des gènes impliqués dans la transcription, la réplication à proximité de l'origine de réplication sur le brin direct, et le biais de séquence observé le long des réplichores, ont une influence à long terme. Au contraire, la symétrie de réplichore a une influence à court terme. Si la perturbation de l'organisation en macrodomaine est le plus souvent bien tolérée par la cellule, deux types d'inversions affectent sévèrement la physiologie de la cellule : l une impliquant le macrodomaine Ori et l'autre le macrodomaine Ter. La délocalisation de la fin de la réplication en dehors du macrodomaine Ter est très bien tolérée pas la cellule. Par contre, lorsqu une petite portion de macrodomaine Ter est présente au niveau du nouveau terminus de réplication, la configuration chromosomique devient instable et nécessite RecA pour la viabilité. Des étapes post-réplicatives seraient affectées. RecA est importante de par son activité de recombinaison et parce qu'elle permet l'activation d'une réponse dite réponse SOS, qui permettrait à la cellule d'éviter de finir la réplication dans la région délocalisée.Knowledge of forces limiting genome plasticity could improve the general understanting of cell functioning. Most bacterial genomes are circular molecules, and DNA replication proceeds in two directions from a single origin to an opposite region where replication forks meet. Chromosomes were rearranged by large inversions. The respective effects of the rearrangements were assessed. The results show that the preferential positioning of essential genes on the leading strand, the proximity of genes involved in transcription and translation to the origin of replication on the leading strand, and the presence of biased sequences along the replichores operate only as long-term positive selection determinants. By contrast, selection operates to maintain replication arms of similar lengths. If modifying the macrodomain organization is most ofen well tolerated by the cell, two types of inversions severely affect the cell cycle. One involves the Ori macrodomain and the other involves the Ter macrodomain. In an interesting way, the positioning of the replication terminus outside the Ter macrodomain is well tolerated by the cell. On the contrary, when a portion of Ter macrodomain is present in the new zone where replication terminates, the cell physiology is severely affected. This configuration is unstable and RecA becomes essential for viability. Essential post-replication steps, that remain to be identified, seem to be inhibited. The role of RecA is important because of its recombination activity and its capacity to activate the SOS response. The SOS response probably allows replication to terminate outside the mispositionned terminus of replication.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Yersinia enterocolitica prevalence, on fresh pork, poultry and beef meat at retail level, in France

Y. enterocolitica is a zoonotic agent, and the third bacterial cause of human entiritis in Europe. The objective of this study was to assess consumer exposure to the pathogen Y. enterocolitica through meat consumption over a one-year period, in France. In this context, the prevalence of Y. enterocolitica was established on samples of fresh pork, beef and poultry collected at retail level in France. Of the 649 samples, 5.1% (34) were positive for Y. enterocolitica. No significant difference in prevalence between the categories of fresh meat was observed: the prevalence was 5.2 % for pork, 5.2% for beef and 5.9% for poultry meat. However, tongues of pork were highly contaminated by Y. enterocolitica (12.5%) compared to other type of meat.</p

Spermatogenesis in the carnivorous sponge Lycopodina hypogea (Porifera, Demospongiae)

International audienceCarnivorous sponges (family Cladorhizidae) lack the aquiferous system and choanocytes and, therefore, their reproduction and in particular spermatogenesis is unusual for Porifera. We studied spermatogenesis in a carnivorous sponge Lycopodina hypogea using confocal microscopy, SEM and TEM. In brief, spermatogenesis in L. hypogea proceeds as follows. Male cells derive from archaeocyte-like cells. During its first divisions, the spermatogonia are surrounded by a thin follicle made up by a single cell. The spermatogonia divide mitotically, giving rise to next generation of spermatogonia, primary spermatocytes and secondary spermatocytes. Spermatozoa of L. hypogea are long and narrow mono-flagellated cells, tightly packed inside the spermatic cyst. They are unusual for sponges, being dart-shaped, with an anterior filament, which is an electron-dense, rod-like outgrowth terminating in an acrosome. The flagellum is long, and its proximal region is located within a cytoplasmic tunnel. In the course of spermiogenesis, a secondary envelope made up by several cells tightly intertwined by their pseudo-podia is formed around the first unicellular envelope. Symbiotic bacteria are usually present between the sperm cells. During maturation, the sperm cyst, which may be called the spermatophore, migrates from the sponge body to the filaments and acquires two bundles of forceps spicules. Mature spermatophores are released from the filaments. To sum up, we showed that spermatogenesis and fertilization in L. hypogea are strikingly different from these processes in other sponges. The differences mostly concern the origin of male germ cells, the structure of mature spermatozoa and the formation of spermatophores

Diversity of Yersinia enterocolitica population in a slaughterhouse between 2009 and 2010 and discrimination ability of MLVA compared to PFGE

Yersiniosis is a human disease mainly due to the ingestion of raw or undercooked pork meat contaminated mostly with Yersinia enterocolitica (Ye). In France, 74.3% of pig batches at slaughterhouses carried pathogenic Ye. Among them, biotype 4 (BT4) and biotype 3 (BT3) were often recovered. PFGE is one of the most used methods to type Ye, with the restriction enzymes, XbaI and NotI. Nevertheless, MLVA method based on the diversity of six loci tends to replace PFGE; this method showed a higher discriminatory power in others studies. We investigated the genetic diversity of Ye strains isolated in 2009 and in 2010 in one pig slaughterhouse in France and compared the ability of MLVA and PFGE to discriminate the strains. During these two years, 335 isolates were collected from pigs. The BT4 represented 88.4% of the strains (296/335) and the BT3 only 11.6% (39/335). PFGE using XbaI enzyme allowed the identification of 12 XbaI-PFGE types and among them only one was common to the both surveys. Because the Simpson’s Index shows a low genetic diversity 31 BT4 strains and 39 BT3 strains were typed using MLVA. For BT3 strains, MLVA had the same index of diversity than PFGE (DI=0.472). In contrary, the index of diversity was significantly higher with MLVA (DI=0.871) than with PFGE (DI=0.665) for BT4 strains. Our study revealed that the population of Ye in pig varied over the time. The comparison of the both typing methods indicated that MLVA has a better discriminatory power than XbaI-PFGE method for BT4 strains but not for BT3 strains.</p

In vitro characterization of the ability of Yersinia enterocolitica BT4 to colonize pigs and stainless steel surfaces

Yersiniosis is, after campylobacteriosis and salmonellosis, the third most frequently reported zoonosis in Europe. Humans become infected with Y. enterocolitica through the consumption of undercooked pork and raw food having been in contact with contaminated surfaces. Pigs, the main reservoir for human pathogenic strains, do not develop clinical signs. In France and worldwide, biotype 4 (BT4) is the biotype the most frequently isolated from both pigs and clinical yersiniosis. In this study, a collection of 26 pathogenic BT4 strains isolated from pig tonsils was used to investigate their ability to adhere and invade intestinal pig cells (IPEC-J2) and to adhere to abiotic surfaces (stainless steel coupons) using two in vitro tests. Regression analysis was performed between data sets obtained from IPECJ2 cells assays versus stainless steel assays. All BT4 strains were able to adhere and invade IPEC-J2 cells. However, the results showed heterogeneity between strains with respect to their ability to adhere to IPECJ2 cells, with a percentage of adhesion varying from 9% to more than 90%. The BT4 population displayed a more homogeneous ability to invade IPECJ2 cells with percentages varying from 10% to 26%. The BT4 strains displayed a great ability to adhere to the stainless steel surface, percentage of adhesion varying from 0.3% to 4.2%. No correlation was observed between IPEC-J2 cell adhesion, cell invasion and adhesion to the stainless steel surface (R² < 0.02). In conclusion, these results reflect the ability of the different BT4 strains to colonize the intestinal tract of pigs and to contaminate the stainless steel surfaces of the food processing environment.</p