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Accueil > Pages Perso > Estelle LOUKIADIS

Equipe de Recherche Bactéries Pathogènes et Opportunistes de l’Environnement

Estelle LOUKIADIS

Docteur vétérinaire, Inspecteur de la Santé Publique Vétérinaire, Chercheur en Ecologie Microbienne

Activité

  • Thèmes de recherches :
    1. Biogéographie et matrices (sources, transferts et dynamiques)
    2. Structure et diversité des populations (phénotype, génotype, génome)
    3. Expologie (exposition et épidémiologie)
    4. Adaptations génétiques aux contraintes environnementales (virulence, fonctions extérieures)

Parcours scientifique

  • Thèse de Doctorat vétérinaire. 2002. Faculté de Médecine de Lyon.
  • Certificat d’études approfondies vétérinaires (CEAV) de Santé Publique. 2003. Ecole Nationale des Services Vétérinaires.
  • Titularisation dans le corps des Inspecteurs de la Santé Publique Vétérinaire (ISPV). 2003. Ecole Nationale des Services Vétérinaires.
  • Thèse de troisième cycle universitaire en microbiologie. 2007. Université Paul Sabatier de Toulouse.

Publications

2016



  • Bonanno L, Petit M-A, Loukiadis E, Michel V, Auvray F. 2016. Heterogeneity in Induction Level, Infection Ability, and Morphology of Shiga Toxin-Encoding Phages (Stx Phages) from Dairy and Human Shiga Toxin-Producing Escherichia coli O26:H11 Isolates Dudley, EG. Applied and Environmental Microbiology. 82:2177-2186. doi: 10.1128/AEM.03463-15.
    Résumé : Shiga toxin (Stx)-producing Escherichia coli (STEC) bacteria are foodborne pathogens responsible for diarrhea and hemolytic-uremic syndrome (HUS). Shiga toxin, the main STEC virulence factor, is encoded by the stx gene located in the genome of a bacteriophage inserted into the bacterial chromosome. The O26:H11 serotype is considered to be the second-most-significant HUS-causing serotype worldwide after O157:H7. STEC O26:H11 bacteria and their stx-negative counterparts have been detected in dairy products. They may convert from the one form to the other by loss or acquisition of Stx phages, potentially confounding food microbiological diagnostic methods based on stx gene detection. Here we investigated the diversity and mobility of Stx phages from human and dairy STEC O26:H11 strains. Evaluation of their rate of in vitro induction, occurring either spontaneously or in the presence of mitomycin C, showed that the Stx2 phages were more inducible overall than Stx1 phages. However, no correlation was found between the Stx phage levels produced and the origin of the strains tested or the phage insertion sites. Morphological analysis by electron microscopy showed that Stx phages from STEC O26:H11 displayed various shapes that were unrelated to Stx1 or Stx2 types. Finally, the levels of sensitivity of stx-negative E. coli O26:H11 to six Stx phages differed among the 17 strains tested and our attempts to convert them into STEC were unsuccessful, indicating that their lysogenization was a rare event.
    Mots-clés : #6, #vetagrosup, Bacteriophages, converting phages, genes, Hemolytic-Uremic Syndrome, in-vivo, minced beef, quantification, Real-time PCR, sos regulatory system, strains.


  • Douëllou T, et al. 2016. Shiga toxin-producing Escherichia coli strains isolated from dairy products — Genetic diversity and virulence gene profiles. International Journal of Food Microbiology. 232:52-62. doi: 10.1016/j.ijfoodmicro.2016.04.032.
    Résumé : Shiga toxin-producing Escherichia coli (STEC) are widely recognized as pathogens causing food borne disease. Here we evaluate the genetic diversity of 197 strains, mainly STEC, from serotypes O157:H7, O26:H11, O103:H2, O111:H8 and O145:28 and compared strains recovered in dairy products against strains from human, meat and environment cases. For this purpose, we characterized a set of reference-collection STEC isolates from dairy products by PFGE DNA fingerprinting and a subset of these by virulence-gene profiling. PFGE profiles of restricted STEC total DNA showed high genomic variability (0.9976 on Simpson's discriminatory index), enabling all dairy isolates to be differentiated. High-throughput real-time PCR screening of STEC virulence genes were applied on the O157:H7 and O26:H11 STEC isolates from dairy products and human cases. The virulence gene profiles of dairy and human STEC strains were similar. Nevertheless, frequency-wise, stx1 was more prevalent among dairy O26:H11 isolates than in human cases ones (87% vs. 44%) while stx2 was more prevalent among O26:H11 human isolates (23% vs. 81%). For O157:H7 isolates, stx1 (0% vs. 39%), nleF (40% vs 94%) and Z6065 (40% vs 100%) were more prevalent among human than dairy strains. Our data point to differences between human and dairy strains but these differences were not sufficient to associate PFGE and virulence gene profiles to a putative lower pathogenicity of dairy strains based on their lower incidence in disease. Further comparison of whole-genome expression and virulence gene profiles should be investigated in cheese and intestinal tract samples.
    Mots-clés : #6, #vetagrosup, Biodiversity, Dairy products, Genetic, STEC.


  • Kerangart S, et al. 2016. Variable tellurite resistance profiles of clinically-relevant Shiga toxin-producing Escherichia coli (STEC) influence their recovery from foodstuffs. Food Microbiology. 59:32-42. doi: 10.1016/j.fm.2016.05.005.
    Résumé : Tellurite (Tel)-amended selective media and resistance (Tel-R) are widely used for detecting Shiga toxin-producing Escherichia coli (STEC) from foodstuffs. Tel-R of 81 O157 and non-O157 STEC strains isolated from animal, food and human was thus investigated. Variations of STEC tellurite minimal inhibitory concentration (MIC) values have been observed and suggest a multifactorial and variable tellurite resistome between strains. Some clinically-relevant STEC were found highly susceptible and could not be recovered using a tellurite-based detection scheme. The ter operon was highly prevalent among highly Tel-R STEC but was not always detected among intermediately-resistant strains. Many STEC serogroup strains were found to harbor sublines showing a gradient of MIC values. These Tel-R sublines showed statistically significant log negative correlations with increasing tellurite concentration. Whatever the tellurite concentration, the highest number of resistant sublines was observed for STEC belonging to the O26 serogroup. Variations in the number of these Tel-R sublines could explain the poor recovery of some STEC serogroups on tellurite-amended media especially from food products with low levels of contamination. Comparison of tellurite MIC values and distribution of virulence-related genes showed Tel-R and virulence to be related.
    Mots-clés : #6, #vetagrosup, Foodstuff, selective media, STEC, Tellurite resistance, ter genes.

2015



  • Bonanno L, et al. 2015. Diversity of Shiga toxin-producing Escherichia coli (STEC) O26:H11: characterization of stx subtypes and insertion sites of Stx and EspK bacteriophages. Applied and Environmental Microbiology. AEM.00077-15. doi: 10.1128/AEM.00077-15.
    Résumé : Shiga toxin-producing Escherichia coli (STEC) are food-borne pathogens that may be responsible for severe human infections. Only a limited number of serotypes, including O26:H11, are involved in the majority of serious cases and outbreaks. The main virulence factors, Shiga-toxins (Stx), are encoded by bacteriophages. Seventy four STEC O26:H11 strains of various origins (including human, dairy and cattle) were characterized for their stx subtypes and Stx phage chromosomal insertion sites. The majority of food and cattle strains possessed the stx1a subtype, while human strains mainly carried either stx1a or stx2a. The wrbA and yehV genes were the main Stx phage insertion sites in STEC O26:H11, followed distantly by yecE and sbcB. Interestingly, the occurrence of Stx phages inserted into the yecE gene was low in dairy strains. In most of 29 stx-negative E. coli O26:H11 strains also studied here, these bacterial insertion sites were vacant. Multilocus sequence typing of 20 stx-positive or stx-negative E. coli O26:H11 showed that they were distributed into two phylogenetic groups defined by sequence type (ST) 21 and ST29. Finally, an EspK-carrying phage was found inserted into the ssrA gene in the majority of STEC O26:H11 but only in a minority of stx-negative E. coli O26:H11. The differences of stx subtypes and Stx phage insertion sites observed in STEC O26:H11 according to their origin might reflect that strains circulating in cattle and foods are clonally distinct from those isolated from human patients.


  • Galia W, et al. 2015. Genome Sequence and Annotation of a Human Infection Isolate of Escherichia coli O26:H11 Involved in a Raw Milk Cheese Outbreak. Genome Announcements. 3:e01568-14. doi: 10.1128/genomeA.01568-14.
    Résumé : The consumption of raw milk cheese can expose populations to Shiga toxin-producing Escherichia coli (STEC). We report here the genome sequence of an E. coli O26:H11 strain isolated from humans during the first raw milk cheese outbreak described in France (2005).
    Mots-clés : #6.

  • Wheeler SR, et al. 2015. Detection of Non-O157 Shiga Toxin–Producing Escherichia coli in 375 Grams of Beef Trim Enrichments across Multiple Commercial PCR Detection Platforms. Journal of Food Protection. 78:196-202. doi: 10.4315/0362-028X.JFP-14-263.
    Résumé : Although serotype O157:H7 remains the pathogenic Shiga toxin–producing Escherichia coli (STEC) of primary concern worldwide, some focus in the United States has shifted to six particular non-O157 STEC serogroups (O26, O45, O103, O111, O121, and O145). Some of these serogroups have also emerged as concerns elsewhere around the world, including Europe. The objective of this work was to compare commercial detection methods with the U.S. Department of Agriculture (USDA) reference method for detection of non-O157 STEC in 375 g of beef trim using a limit of detection study design. Overall, the commercial platforms performed well, showing similar levels of sensitivity for detection of presumptive positives for O45, O26, O103, and O121 (PCR screen results only). For O111, one method that utilizes an integrated immunomagnetic separation and PCR approach was more sensitive than a PCR-only screen approach. Additionally, one commercial method showed more presumptive and confirmed positives overall. Use of an immunomagnetic separation tool, such as antibody-coated beads, aided considerably with the confirmation procedures and is an important step when confirming suspect samples. A secondary goal of this study was to evaluate isolation and International Organization for Standardization confirmation protocols used in Europe compared with strategies provided by the USDA Microbiology Laboratory Guidebook (MLG). Generally, results from the USDA confirmation plates (modified Rainbow agar) were better than the European Union confirmation plates (MacConkey agar with or without rhamnose). In summary, detection of non-O157 STEC in 375 g of beef trim can be performed by any of the three methods on the market evaluated in the study.
    Mots-clés : #6.

2014



  • Bibbal D, et al. 2014. Slaughterhouse effluent discharges into rivers not responsible for environmental occurrence of enteroaggregative Escherichia coli. Veterinary Microbiology. 168:451-454. doi: 10.1016/j.vetmic.2013.11.042.
    Résumé : Enteroaggregative Shiga-toxin-producing Escherichia coli strains were responsible for a massive outbreak in Europe in 2011, and had been previously isolated from French patients. The objective of this study was to investigate the presence of enteroaggregative E. coli (EAEC) in slaughterhouse effluents (wastewater, slurry, sludge and effluents), and in river waters near these slaughterhouses. A total of 10,618 E. coli isolates were screened by PCR for the presence of EAEC-associated genetic markers (aggR, aap and aatA). None of these markers was detected in E. coli isolated from slaughterhouse samples. A unique enteroaggregative E. coli (EAEC) O126:H8 was detected in river water sampled upstream from slaughterhouse effluent discharge. These results confirmed that animals might not be reservoirs of EAEC, and that further studies are required to evaluate the role of the environment in the transmission of EAEC to humans.
    Mots-clés : #6, Cattle, E. coli, EAEC, Effluent, Slaughterhouse, STEC.

  • Bibbal D, et al. 2014. Prevalence of carriers of Shiga toxin-producing Escherichia coli serotypes O157:H7, O26:H11, O103:H2, O111:H8 and O145:H28 in French slaughtered adult cattle. Applied and Environmental Microbiology. doi: 10.1128/AEM.03315-14.
    Résumé : The main pathogenic enterohemorrhagic Escherichia coli (EHEC) are defined as Shiga toxin (Stx)-producing E. coli (STEC) belonging to one of the following serotypes: O157:H7, O26:H11, O103:H2, O111:H8 and O145:H28. Each of these five serotypes is known to be associated with a specific subtype of the intimin-encoding gene (eae). The objective of this study was to evaluate the prevalence of bovine carriers of these 'top five' STEC in the four adult cattle categories slaughtered in France. Fecal samples were collected from 1,318 cattle, including 291 young dairy bulls, 296 young beef bulls, 337 dairy cows and 394 beef cows. A total of 96 E. coli isolates including 33 'top five' STEC and 63 atypical enteropathogenic E. coli (aEPEC), with the same genetic characteristics as 'top five' STEC strains except that they lacked an stx gene, were recovered from these samples. O157:H7 was the most frequently isolated STEC serotype. The prevalence of 'top five' STEC (all serotypes included) was 4.5% in young dairy bulls, 2.4% in young beef bulls, 1.8% in dairy cows and 1.0% in beef cows. It was significantly highest in young dairy bulls (p<0.05) compared to the other 3 categories. The basis for these differences between categories remains to be elucidated. Moreover, simultaneous carriage of STEC O26:H11 and STEC O103:H2 was detected in one young dairy bull. Lastly, the prevalence of bovine carriers of 'top five' STEC, evaluated through a weighted arithmetic mean of the prevalence by categories, was estimated to 1.8% in French slaughtered adult cattle.
    Mots-clés : #6.


  • Bibbal D, et al. 2014. Intimin gene (eae) subtypes-based real-time PCR strategy for the specific detection of Shiga toxin-producing Escherichia coli serotypes O157:H7, O26:H11, O103:H2, O111:H8 and O145:H28 in cattle feces. Applied and Environmental Microbiology. AEM.03161-13. doi: 10.1128/AEM.03161-13.
    Résumé : Shiga toxin-producing Escherichia coli (STEC) belonging to serotypes O157:H7, O26:H11, O103:H2, O111:H8 and O145:H28 are known to be associated with particular subtypes of the intimin gene (eae), namely γ1, β1, ɛ, θ and γ1, respectively. This study aimed at evaluating the usefulness of their detection for the specific detection of these five main pathogenic STEC serotypes in cattle feces. Using real-time PCR assays, 58.7% of 150 fecal samples were found positive for at least one of the four targeted eae subtypes. The simultaneous presence of stx, eae and one of the five O group markers was found in 58.0% of the samples, and the five targeted stx/eae/O genetic combinations were detected 143 times. However, when taking into consideration the association between eae subtypes and O group markers, the resulting stx/eae-subtype/O combinations were detected only 46 times. The 46 isolation assays performed allowed to recover 22 E. coli strains belonging to one of the five targeted STEC serogroups. By contrast, only 2 out of 39 isolation assays performed on samples that were positive for stx, eae and an O group marker, but were negative for the corresponding eae subtype, were successful. Characterization of the 24 E. coli isolates showed that 6 were STEC, including 1 O157:H7, 3 O26:H11 and 2 O145:H28. The remaining 18 strains corresponded to atypical enteropathogenic E. coli (aEPEC). Finally, the more discriminating eae subtypes-based PCR strategy described here may be helpful for the specific screening of the five major STEC in cattle feces.


  • Chagnot C, et al. 2014. Colonization of the meat extracellular matrix proteins by O157 and non-O157 enterohemorrhagic Escherichia coli. International Journal of Food Microbiology. doi: 10.1016/j.ijfoodmicro.2014.07.016.
    Résumé : Enterohemorrhagic Escherichia coli (EHEC) are anthropozoonotic agents that range third among food-borne pathogens respective to their incidence and dangerousness in the European Union. EHEC are Shiga-toxin producing E. coli (STEC) responsible for foodborne poisoning mainly incriminated to the consumption of contaminated beef meat. Among the hundreds of STEC serotypes identified, EHEC mainly belong to O157:H7 but non-O157 can represent 20 to 70 % of EHEC infections per year. Seven of those serogroups are especially of high-risk for human health, i.e. O26, O45, O103, O111, O121, O145 and O104. While meat can be contaminated all along the food processing chain, EHEC contamination essentially occurs at the dehiding stage of slaughtering. Investigating bacterial colonization to the skeletal-muscle extracellular matrix (ECM) proteins, it appeared that environmental factors influenced specific and non-specific bacterial adhesion of O157 and non-O157 EHEC as well as biofilm formation. Importantly, mechanical treatment (i.e. shaking, centrifugation, pipetting and vortexing) inhibited and biased the results of bacterial adhesion assay. Besides stressing the importance of the protocol to investigate bacterial adhesion to ECM proteins, this study demonstrated that the colonization abilities to ECM proteins varies among EHEC serogroups and should ultimately be taken into consideration to evaluate the risk of contamination for different type of food matrices.
    Mots-clés : bacterial adhesion, Biofilm formation, Enterohemorrhagic Escherichia coli, Extracellular matrix protein, Meat contamination, Shiga-toxin producing E. coli.


  • King LA, et al. 2014. Foodborne transmission of sorbitol-fermenting Escherichia coli O157:[H7] via ground beef: an outbreak in northern France, 2011. Clinical Microbiology and Infection. n/a-n/a. doi: 10.1111/1469-0691.12736.
    Résumé : Sorbitol-fermenting Escherichia coli O157:[H7] is a particularly virulent clone of E. coli O157:H7 associated with a higher incidence of haemolytic uraemic syndrome and a higher case fatality rate. Many fundamental aspects of its epidemiology remain to be elucidated including its reservoir and transmission routes and vehicles. We describe an outbreak of sorbitol-fermenting E. coli O157:[H7] that occurred in France in 2011. Eighteen cases of paediatric haemolytic uremic syndrome with symptom onset between 6 June and 15 July 2011 were identified among children aged 6 months to 10 years residing in northern France. A strain of sorbitol-fermenting E. coli O157:[H7] stx2a eae was isolated from 10 cases. Epidemiological, microbiological and trace-back investigations identified multiply-contaminated frozen ground beef products bought in a supermarket chain as the outbreak vehicle. Strains with three distinct pulsotypes that were isolated from patients, ground beef preparations recovered from patients’ freezers and from stored production samples taken at the production plant were indistinguishable upon molecular comparison. This investigation documents microbiologically confirmed food-borne transmission of sorbitol-fermenting of E. coli O157 via beef and could additionally provide evidence of a reservoir in cattle for this pathogen. This article is protected by copyright. All rights reserved.
    Mots-clés : E. coli O157, France, haemolytic uraemic syndrome, HUS, Outbreak, Shiga toxin-producing E. coli, STEC.

2013


  • Barret A-S, et al. 2013. Shopper cards data and storage practices for the investigation of an outbreak of Shiga-toxin producing Escherichia coli O157 infections. Médecine Et Maladies Infectieuses. 43:368-373. doi: 10.1016/j.medmal.2013.05.004.
    Résumé : INTRODUCTION: An outbreak of shiga-toxin producing Escherichia coli infections occurred in southwest France in June 2012. The outbreak was investigated to identify the source of infection, and guide control measures. METHODS: Confirmed outbreak cases were patients who developed bloody diarrhoea or haemolytic uremic syndrome (HUS) between 28 May and 6 July 2012, with E. coli O157 isolates showing indistinguishable patterns on pulse field gel electrophoresis (PFGE). A standardized questionnaire was administered to patients to document food consumption and other risk exposures. Their purchase was checked through their supermarket shopper card data. RESULTS: Six patients (four with HUS and two with bloody diarrhea) were confirmed outbreak cases. Fresh ground beef burgers from one supermarket were the only common food exposure, identified by interviews and shopper card data. The PFGE profile of shiga toxin-producing E. coli O157 isolated from the suspected beef burgers was identical to those from the human cases. The suspected beef burgers were no longer on sale at the time of investigation but three patients confirmed as outbreak cases had deep-frozen some at home. CONCLUSION: Shopper card data was particularly useful to obtain precise and reliable information on the traceability of consumed food. Despite the expired use-by date, a recall was issued for the beef burgers. This contributed to preventing other cases among consumers who had deep-frozen the beef burgers.
    Mots-clés : #6, Animals, Bacterial Typing Techniques, Cattle, Cryopreservation, Disease Outbreaks, Escherichia coli Infections, Escherichia coli O157, Food Contamination, Food Preservation, Food Storage, France, Genes, Bacterial, Hemolytic-Uremic Syndrome, Humans, Meat Products, Public Health Surveillance, Records as Topic.

2012



  • King LA, et al. 2012. Outbreak of Shiga Toxin-Producing Escherichia coli O104:H4 Associated With Organic Fenugreek Sprouts, France, June 2011. Clinical Infectious Diseases. 54:1588-1594. doi: 10.1093/cid/cis255.
    Mots-clés : #6.


  • Miszczycha SD, et al. 2012. Novel Real-Time PCR Method To Detect &lt;I&gt;Escherichia&lt;/I&gt; &lt;I&gt;coli&lt;/I&gt; O157:H7 in Raw Milk Cheese and Raw Ground Meat. Journal of Food Protection. 75:1373-1381. doi: 10.4315/0362-028X.JFP-11-498.
    Mots-clés : #6.

2011



  • Bugarel M, Beutin L, Scheutz F, Loukiadis E, Fach P. 2011. Identification of Genetic Markers for Differentiation of Shiga Toxin-Producing, Enteropathogenic, and Avirulent Strains of Escherichia coli O26. Applied and Environmental Microbiology. 77:2275-2281. doi: 10.1128/AEM.02832-10.
    Mots-clés : #6.


  • Madic J, et al. 2011. Duplex real-time PCR detection of type III effector tccP and tccP2 genes in pathogenic Escherichia coli and prevalence in raw milk cheeses: tccP/tccP2 real-time PCR detection. Letters in Applied Microbiology. 52:538-545. doi: 10.1111/j.1472-765X.2011.03038.x.
    Mots-clés : #6.

  • Neto M, Skorski G, Thevenot-Sergentet D, Loukiadis E. 2011. Optical maps: methodology and applications in microbiology. http://www.phylogene.com/Local/phylogene/files/40/Neto.M.and.all.Euroreference.n_5.summer.2011.Mini-review.-.Optical.maps.methodology.and.applications.pdf.

2008


  • Loukiadis E, et al. 2008. Distribution, functional expression, and genetic organization of Cif, a phage-encoded type III-secreted effector from enteropathogenic and enterohemorrhagic Escherichia coli. Journal of Bacteriology. 190:275-285. doi: 10.1128/JB.00844-07.
    Résumé : Enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic E. coli (EHEC) inject effector proteins into host cells via a type III secretion system encoded by the locus of enterocyte effacement (LEE). One of these effectors is Cif, encoded outside the LEE by a lambdoid prophage. In this study, we demonstrated that the Cif-encoding prophage of EPEC strain E22 is inducible and produces infectious phage particles. We investigated the distribution and functional expression of Cif in 5,049 E. coli strains of human, animal, and environmental origins. A total of 115 E. coli isolates from diverse origins and geographic locations carried cif. The presence of cif was tightly associated with the LEE, since all the cif-positive isolates were positive for the LEE. These results suggested that the Cif-encoding prophages have been widely disseminated within the natural population of E. coli but positively selected within the population of LEE-positive strains. Nonetheless, 66% of cif-positive E. coli strains did not induce a typical Cif-related phenotype in eukaryotic cells due to frameshift mutations or insertion of an IS element in the cif gene. The passenger region of the prophages carrying cif was highly variable and showed various combinations of IS elements and genes coding for other effectors such as nleB, nleC, nleH, nleG, espJ, and nleA/espI (some of which were also truncated). This diversity and the presence of nonfunctional effectors should be taken into account to assess EPEC and EHEC pathogenicity and tropism.
    Mots-clés : Bacteriophages, DNA, Bacterial, Enterohemorrhagic Escherichia coli, Enteropathogenic Escherichia coli, Escherichia coli Proteins, Genes, Bacterial, Molecular Sequence Data, Phenotype, Phylogeny, Prophages, Virulence.

2006


  • Loukiadis E, Kérourédan M, Beutin L, Oswald E, Brugère H. 2006. Characterization of Shiga toxin gene (stx)-positive and intimin gene (eae)-positive Escherichia coli isolates from wastewater of slaughterhouses in France. Applied and Environmental Microbiology. 72:3245-3251. doi: 10.1128/AEM.72.5.3245-3251.2006.
    Résumé : Wastewater samples from 12 slaughterhouses located in different regions in France were tested for the presence of stx-positive and eae-positive Escherichia coli isolates, and characteristics of the isolates obtained were determined. A total of 224 wastewater samples were collected in wastewater treatment plants at different stages of wastewater processing. Altogether, 5,001 E. coli isolates were obtained by colony counting and screened for the presence of stx and eae genes by multiplex PCR. stx-positive and eae-positive E. coli isolates were detected in 25% of the samples collected; they were found in 13% and 3% of the samples obtained from treated effluent and sludge, respectively, suggesting that they could be spread into the environment. Screening of the samples collected by immunomagnetic separation allowed us to isolate 31 additional E. coli serogroup O157 isolates. Four of these isolates harbored stx and eae genes. All stx-positive and eae-positive E. coli isolates were analyzed for eae and stx genetic variants, as well as for additional virulence factors and serotypes. Our results suggest that the majority of the stx- and eae-positive E. coli isolates from wastewater have low virulence for humans. However, the diversity of the enterohemorrhagic E. coli-associated virulence factors in the strains indicates that the environment may play an important role in the emergence of new pathogenic enterohemorrhagic E. coli strains.
    Mots-clés : Abattoirs, Adhesins, Bacterial, Animals, Escherichia coli, Escherichia coli O157, Escherichia coli Proteins, France, Fresh Water, HeLa Cells, Humans, Rivers, Serotyping, Shiga Toxin, Virulence, Waste Disposal, Fluid.

Année non précisée



  • Douëllou T, et al. sans date. Molecular characterization of O157:H7, O26:H11 and O103:H2 Shiga toxin-producing Escherichia coli isolated from dairy products. International Journal of Food Microbiology. doi: 10.1016/j.ijfoodmicro.2017.04.010.
    Résumé : Pathogenic Shiga toxin-producing E. coli (STEC) are recognized worldwide as environment and foodborne pathogens which can be transmitted by ingestion of ready-to-eat food such as raw milk-derived products. STEC show a prevalence rate in dairy products of 0.9%, yet comparably few outbreaks have been related to dairy products consumption. In this study, we used rt-qPCR to identify the virulence potential of O157, O26 and O103 STEC strains isolated from raw-milk dairy products by analyzing virulence-related gene frequencies and associations with O-island (OI) 44, OI-48, OI-50, OI-57, OI-71 and OI-122. Results showed that 100% of STEC strains investigated harbored genes associated with EHEC-related virulence profile patterns (eae and stx, with either espK, espV, ureD and/or Z2098). We also found similarities in virulence-related gene content between O157:H7 and O103:H2 dairy and non-dairy STEC strains, especially isolates from human cases. The O26:H11-serotype STEC strains investigated harbor the arcA-allele 2 gene associated with specific genetic markers. These profiles are associated with high-virulence seropathotype-A STEC. However, the low frequency of stx2 gene associated with absence of other virulence genes in dairy isolates of O26:H11 remains a promising avenue of investigation to estimate their real pathogenicity. All O26:H11 attaching-effacing E. coli (AEEC) strains carried CRISPRO26:H11 SP_O26_E but not genetic markers espK, espV, ureD and/or Z2098 associated with the emerging potentially high-virulence “new French clone”. These strains are potentially as “EHEC-like” strains because they may acquire (or have lost) stx gene. In this study, O157:H7, O103:H2 and O26:H11 STEC strains isolated from dairy products were assigned as potential pathogens. However, research now needs to investigate the impact of dairy product environment and dairy processing on the expression of their pathogenicity.
    Mots-clés : #6, Dairy products, Non-O157 STEC, O157 STEC, Virulence genetic markers.


  • Loukiadis E, et al. sans date. Distribution of Escherichia coli O157:H7 in ground beef: Assessing the clustering intensity for an industrial-scale grinder and a low and localized initial contamination. International Journal of Food Microbiology. doi: 10.1016/j.ijfoodmicro.2017.03.009.
    Résumé : Undercooked ground beef is regularly implicated in food-borne outbreaks involving pathogenic Shiga toxin-producing Escherichia coli. The dispersion of bacteria during mixing processes is of major concern for quantitative microbiological risk assessment since clustering will influence the number of bacteria the consumers might get exposed to as well as the performance of sampling plans used to detect contaminated ground beef batches. In this study, batches of 25 kg of ground beef were manufactured according to a process mimicking an industrial-scale grinding with three successive steps: primary grinding, mixing and final grinding. The ground beef batches were made with 100% of chilled trims or with 2/3 of chilled trims and 1/3 of frozen trims. Prior grinding, one beef trim was contaminated with approximately 106–107 CFU of E. coli O157:H7 on a surface of 0.5 cm2 to reach a concentration of 10–100 cells/g in ground beef. The E. coli O157:H7 distribution in ground beef was characterized by enumerating 60 samples (20 samples of 5 g, 20 samples of 25 g and 20 samples of 100 g) and fitting a Poisson-gamma model to describe the variability of bacterial counts. The shape parameter of the gamma distribution, also known as the dispersion parameter reflecting the amount of clustering, was estimated between 1.0 and 1.6. This k-value of approximately 1 expresses a moderate level of clustering of bacterial cells in the ground beef. The impact of this clustering on the performance of sampling strategies was relatively limited in comparison to the classical hypothesis of a random repartition of pathogenic cells in mixed materials (purely Poisson distribution instead of Poisson-gamma distribution).
    Mots-clés : #6, Frequency distribution, Poisson-gamma distribution, Spatial heterogeneity.

Chapitre d’ouvrages

2010


  • Loukiadis E, Kérourédan M, Oswald E, Brugère H. 2010. Effluents d’abattoir et risque d’émergence. In: Les maladies émergentes: épidémiologie chez le végétal, l'animal et l'homme. Editions Quae p. .
    Résumé : Les maladies émergentes, causes de crises sanitaires potentiellement dévastatrices, représentent un enjeu majeur pour la santé végétale, animale et humaine. Difficiles à anticiper en raison de leur caractère nouveau et imprévisible, elles suscitent une réflexion pluridisciplinaire et une analyse spécifique. L'originalité de cet ouvrage est d'appliquer des concepts d'épidémiologie générale à l'émergence de maladies dans les domaines du végétal, de l'animal et de l'humain. La première partie de l'ouvrage présente les facettes de l'émergence dans ces trois domaines. A partir d'études de cas concrets et de synthèses, les parties suivantes traitent de la détection et de l'analyse biologiques des émergences, de leur traitement statistique et de leur modélisation, des facteurs environnementaux qui les déterminent, et du franchissement de la barrière d'espèces par les virus. La dernière partie de l'ouvrage fait le point sur les politiques nationales et internationales de santé face à ces maladies. Destiné aux étudiants, aux professionnels et aux chercheurs intéressés par une vision globale des maladies émergentes, l'ouvrage s'adresse également à tout public concerné par les problématiques actuelles et futures en santé végétale, animale et humaine.
    Mots-clés : #6.

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