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Santos-Santórum Suárez C, Sanders P, Gaugain M, Viel A, Paboeuf F, Taillandier JF, Houée P, Valentin C, Perrin-Guyomard A. Selection of antibiotic resistance in pigs after exposure to feed cross-contaminated with oxytetracycline. Vet Microbiol 2023; 287:109924. [PMID: 38007921 DOI: 10.1016/j.vetmic.2023.109924] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 10/18/2023] [Accepted: 11/20/2023] [Indexed: 11/28/2023]
Abstract
Due to possible cross-contamination of animal feedstuff with antibiotics, food-producing animals may be exposed to undesirable low concentrations of antimicrobials. These sub-therapeutic levels of antibiotics can lead to the selection of resistant bacteria in the animal gut. The goal of this study was to assess, through analysis of the faeces of treated and control pigs, the risk of resistant E. coli being selected after daily exposure for three weeks to feed contaminated with oxytetracycline at 1% of the therapeutic dose. Liquid Chromatography coupled to tandem Mass Spectrometry was used to determine the oxytetracycline concentrations in faecal samples. In the treated group, concentrations were in the range of 4481.9 - 8671.2 µg/kg. In the control group, these concentrations were either below the method's limit of quantification or up to 60.5 µg/kg. After a transient increase in resistance in both groups, microbiological analysis showed that the treated group had a significantly higher oxytetracycline resistance rate by the end of the study than the control group (p < 0.001). Furthermore, the treated animals were found to select co-resistances to nalidixic acid and ampicillin. Finally, at tolerated antibiotic contamination levels of feed, the treated group had a higher proportion of multidrug-resistant isolates at the end of the study than the control one (p < 0.05). The present study demonstrates that, at the tolerated contamination rates, both antimicrobial resistance and multidrug-resistant bacteria can be selected and evidenced in the gut microbiota.
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Affiliation(s)
- Cristina Santos-Santórum Suárez
- ANSES-Fougères Laboratory (French National Agency for Food, Environment and Occupational Health & Safety), 10 B, rue Claude Bourgelat - Javené, CS 40608, 35306 CEDEX Fougères, France
| | - Pascal Sanders
- ANSES-Fougères Laboratory (French National Agency for Food, Environment and Occupational Health & Safety), 10 B, rue Claude Bourgelat - Javené, CS 40608, 35306 CEDEX Fougères, France
| | - Murielle Gaugain
- ANSES-Fougères Laboratory (French National Agency for Food, Environment and Occupational Health & Safety), 10 B, rue Claude Bourgelat - Javené, CS 40608, 35306 CEDEX Fougères, France
| | - Alexis Viel
- ANSES-Fougères Laboratory (French National Agency for Food, Environment and Occupational Health & Safety), 10 B, rue Claude Bourgelat - Javené, CS 40608, 35306 CEDEX Fougères, France
| | - Frédéric Paboeuf
- ANSES-Ploufragan-Plouzané Laboratory (French National Agency for Food, Environment and Occupational Health & Safety), 22440 Ploufragan, France
| | - Jean-François Taillandier
- ANSES-Fougères Laboratory (French National Agency for Food, Environment and Occupational Health & Safety), 10 B, rue Claude Bourgelat - Javené, CS 40608, 35306 CEDEX Fougères, France
| | - Paméla Houée
- ANSES-Fougères Laboratory (French National Agency for Food, Environment and Occupational Health & Safety), 10 B, rue Claude Bourgelat - Javené, CS 40608, 35306 CEDEX Fougères, France
| | - Charlotte Valentin
- ANSES-Fougères Laboratory (French National Agency for Food, Environment and Occupational Health & Safety), 10 B, rue Claude Bourgelat - Javené, CS 40608, 35306 CEDEX Fougères, France
| | - Agnès Perrin-Guyomard
- ANSES-Fougères Laboratory (French National Agency for Food, Environment and Occupational Health & Safety), 10 B, rue Claude Bourgelat - Javené, CS 40608, 35306 CEDEX Fougères, France.
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Santos-Santórum Suárez C, Sanders P, Perrin-Guyomard A, Hurtaud-Pessel D, Laurentie M, Viel A, Taillandier JF, Lagree MP, Gaugain M. Validation of a LC-MS/MS method for the quantitative analysis of four antibiotics in pig tissues and plasma to assess the risk of transfer of residues to edible matrices after exposure to cross-contaminated feed. Food Addit Contam Part A Chem Anal Control Expo Risk Assess 2022; 39:1818-1827. [PMID: 36194447 DOI: 10.1080/19440049.2022.2126529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/10/2022]
Abstract
Cross-contamination between medicated and non-medicated feed can occur during production, processing, transport or storage of animal feed. This may lead to the presence of low concentrations of antibiotics in supposedly drug-free feed for food production animals, which potentially could also harm consumers due to residues. In addition, consumption of sub-therapeutic concentrations of antibiotics may increase the risk of emergence of resistant bacteria. In this study, LC-MS/MS methods were developed to quantify four antibiotics (sulfadimethoxine, oxytetracycline, trimethoprim and amoxicillin) in several pig matrices, i.e. plasma, muscle, liver, kidneys and faeces. All methods were validated using the accuracy profile, except for amoxicillin in faeces, for which extraction could not be optimised for low concentrations. These methods were then applied as part of an animal study during which several pigs received contaminated feed at a concentration corresponding to 2% of therapeutic dose, in order to evaluate the risk of the presence of residues in animal faeces and tissues. The results showed that sulfadimethoxine is well absorbed and accumulates in the muscle, kidneys and liver, where concentrations were higher than the maximum residue limits (MRLs) authorised in EU legislation. Conversely, oxytetracycline was mostly found in faeces as its oral absorption is very low. Trimethoprim concentrations were slightly higher than the tolerated MRL in the kidneys, but they were below this level in the other tissues. Finally, amoxicillin concentrations remained below the lower limit of quantification of the methods in all matrices.
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Affiliation(s)
- Cristina Santos-Santórum Suárez
- ANSES-Fougères Laboratory (French National Agency for Food, Environment and Occupational Health & Safety), Fougères Cedex, France
| | - Pascal Sanders
- ANSES-Fougères Laboratory (French National Agency for Food, Environment and Occupational Health & Safety), Fougères Cedex, France
| | - Agnès Perrin-Guyomard
- ANSES-Fougères Laboratory (French National Agency for Food, Environment and Occupational Health & Safety), Fougères Cedex, France
| | - Dominique Hurtaud-Pessel
- ANSES-Fougères Laboratory (French National Agency for Food, Environment and Occupational Health & Safety), Fougères Cedex, France
| | - Michel Laurentie
- ANSES-Fougères Laboratory (French National Agency for Food, Environment and Occupational Health & Safety), Fougères Cedex, France
| | - Alexis Viel
- ANSES-Fougères Laboratory (French National Agency for Food, Environment and Occupational Health & Safety), Fougères Cedex, France
| | - Jean-François Taillandier
- ANSES-Fougères Laboratory (French National Agency for Food, Environment and Occupational Health & Safety), Fougères Cedex, France
| | - Marie-Pierre Lagree
- ANSES-Fougères Laboratory (French National Agency for Food, Environment and Occupational Health & Safety), Fougères Cedex, France
| | - Murielle Gaugain
- ANSES-Fougères Laboratory (French National Agency for Food, Environment and Occupational Health & Safety), Fougères Cedex, France
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Liu G, Thomsen LE, Olsen JE. Antimicrobial-induced horizontal transfer of antimicrobial resistance genes in bacteria: a mini-review. J Antimicrob Chemother 2021; 77:556-567. [PMID: 34894259 DOI: 10.1093/jac/dkab450] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The emergence and spread of antimicrobial resistance (AMR) among pathogenic bacteria constitute an accelerating crisis for public health. The selective pressures caused by increased use and misuse of antimicrobials in medicine and livestock production have accelerated the overall selection of resistant bacteria. In addition, horizontal gene transfer (HGT) plays an important role in the spread of resistance genes, for example mobilizing reservoirs of AMR from commensal bacteria into pathogenic ones. Antimicrobials, besides antibacterial function, also result in undesirable effects in the microbial populations, including the stimulation of HGT. The main aim of this narrative review was to present an overview of the current knowledge of the impact of antimicrobials on HGT in bacteria, including the effects of transformation, transduction and conjugation, as well as other less well-studied mechanisms of HGT. It is widely accepted that conjugation plays a major role in the spread of AMR in bacteria, and the focus of this review is therefore mainly on the evidence provided that antimicrobial treatment affects this process. Other mechanisms of HGT have so far been deemed less important in this respect; however, recent discoveries suggest their role may be larger than previously thought, and the review provides an update on the rather limited knowledge currently available regarding the impact of antimicrobial treatment on these processes as well. A conclusion from the review is that there is an urgent need to investigate the mechanisms of antimicrobial-induced HGT, since this will be critical for developing new strategies to combat the spread of AMR.
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Affiliation(s)
- Gang Liu
- College of Veterinary Medicine, Qingdao Agricultural University, Qingdao 266109, China.,Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 1870 Frederiksberg C, Denmark
| | - Line Elnif Thomsen
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 1870 Frederiksberg C, Denmark
| | - John Elmerdahl Olsen
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 1870 Frederiksberg C, Denmark
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In Vitro Assessment of Antimicrobial Resistance Dissemination Dynamics during Multidrug-Resistant-Bacterium Invasion Events by Using a Continuous-Culture Device. Appl Environ Microbiol 2021; 87:AEM.02659-20. [PMID: 33361364 DOI: 10.1128/aem.02659-20] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Accepted: 12/11/2020] [Indexed: 11/20/2022] Open
Abstract
Antimicrobial-resistant pathogens display significant public health threats by causing difficulties in clinical treatment of bacterial infection. Antimicrobial resistance (AMR) is transmissible between bacteria, significantly increasing the appearance of antimicrobial-resistant pathogens and aggravating the AMR problem. In this work, the dissemination dynamics of AMR from invading multidrug-resistant (MDR) Escherichia coli to a community of pathogenic Salmonella enterica was investigated using a continuous-culture device, and the behaviors of dissemination dynamics under different levels of antibiotic stress were investigated. Three MDR E. coli invasion events were analyzed in this work: MDR E. coli-S. enterica cocolonization, MDR E. coli invasion after antibiotic treatment of S. enterica, and MDR E. coli invasion before antibiotic treatment of S. enterica It was found that both horizontal gene transfer (HGT) and vertical gene transfer (VGT) play significant roles in AMR dissemination, although different processes contribute differently under different circumstances, that environmental levels of antibiotics promote AMR dissemination by enhancing HGT rather than leading to selective advantage for resistant bacteria, and that early invasion of MDR E. coli completely and quickly sabotages the effectiveness of antibiotic treatment. These findings contribute to understanding the drivers of AMR dissemination under different antibiotic stresses, the detrimental impact of environmental tetracycline contamination, and the danger of nosocomial presence and dissemination of MDR nonpathogens.IMPORTANCE Antimicrobial resistance poses a grave threat to public health and reduces the effectiveness of antimicrobial drugs in treating bacterial infections. Antimicrobial resistance is transmissible, either by horizontal gene transfer between bacteria or by vertical gene transfer following inheritance of genetic traits. The dissemination dynamics and behaviors of this threat, however, have not been rigorously investigated. In this work, with a continuous-culture device, we studied antimicrobial resistance dissemination processes by simulating antimicrobial-resistant Escherichia coli invasion to a pathogenic Salmonella enterica community. Using this novel tool, we provide evidence on the drivers of antimicrobial resistance dissemination, on the detrimental impact of environmental antibiotic contamination, and on the danger of antimicrobial resistance in hospitals, even if what harbors the antimicrobial resistance is not a pathogen. This work furthers our understanding of antimicrobial resistance and its dissemination between bacteria and of antibiotic therapy, our most powerful tool against bacterial infection.
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Stability, Homogeneity and Carry-Over of Amoxicillin, Doxycycline, Florfenicol and Flubendazole in Medicated Feed and Drinking Water on 24 Pig Farms. Antibiotics (Basel) 2020; 9:antibiotics9090563. [PMID: 32878274 PMCID: PMC7559249 DOI: 10.3390/antibiotics9090563] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 08/27/2020] [Accepted: 08/29/2020] [Indexed: 11/17/2022] Open
Abstract
The vast majority of medicines in pig rearing are administered via oral group medication through medicated feed and drinking water. However, relevant on-farm factors affecting the concentration of these drugs in feed and drinking water, such as the homogeneity, stability, and cross-contamination, are largely unknown. To characterize these factors, samples of medicated feed and drinking water were taken on 24 Belgian pig farms during treatment and 2 days thereafter, as well as at different on-farm sampling sites from production to feeding troughs or drinking nipples. The samples contained amoxicillin, doxycycline, florfenicol, or flubendazole. Additionally, a questionnaire was completed. In contrast to the results of medicated feed, results of medicated water showed a large between-farm variation in antimicrobial drug concentration. The therapeutic concentration range was only met in 2 out of 11 farms using medicated feed, and in 3 out of 13 farms using medicated water. Medicated feed concentrations were often below the therapeutic concentration range mentioned in the Summary of Product Characteristics, while drinking water concentrations were just as often above as they were below the advised target concentration range. Drug residues measured 2 days after the end of therapy with both feed and water medication rarely exceeded 1% of the lowest therapeutic concentration. This study demonstrates that recommendations on good clinical practices for oral group medication in the pig industry are highly needed.
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Vandael F, Filippitzi ME, Dewulf J, Daeseleire E, Eeckhout M, Devreese M, Croubels S. Oral group medication in pig production: characterising medicated feed and drinking water systems. Vet Rec 2019; 185:405. [PMID: 31427411 DOI: 10.1136/vr.105495] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Revised: 07/19/2019] [Accepted: 07/25/2019] [Indexed: 11/04/2022]
Abstract
Despite common use of oral group medication in pig rearing, the homogeneity, stability and carry-over of frequently used medicinal products in feed and drinking water are largely unknown. Therefore, a field study was performed on 52 Belgian pig farms, characterising preparation and administration of medicinal products via these systems, and farmers' user experiences with medicated feed and medicated drinking water. The study showed that medicated drinking water is more commonly used than medicated feed, since 90.4 per cent of the farms sometimes use medicated drinking water and 69.2 per cent of the farms sometimes use medicated feed. The drinking water quality is evaluated at least once a year on only 30.7 per cent of the farms. Separate pipelines for medicated and non-medicated circuits were not present in any of the farms using medicated feed and in 27.7 per cent of the farms using medicated drinking water. With drinking water medication, 63.5 per cent of the farmers reported encountering practical problems, often related to solubility issues and precipitation of the active compounds. In contrast, medicated feed is bought ready-to-use from the feed manufacturer in 68.2 per cent of the cases, thus reducing the number of practical problems experienced by the farmer. This study shows room for improvement of oral group treatment, developing appropriate pharmaceutical formulations for drinking water medication, quality control of drinking water, using separate pipeline circuits, and cleaning and disinfecting protocols.
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Affiliation(s)
- Femke Vandael
- Department of Pharmacology, Toxicology and Biochemistry, Laboratory of Pharmacology and Toxicology, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium
| | | | - Jeroen Dewulf
- Department of Reproduction, Obstetrics and Herd Health, Veterinary Epidemiology Unit, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium
| | - Els Daeseleire
- Technology and Food Science Unit, ILVO, Merelbeke, Belgium
| | - Mia Eeckhout
- Department of Food Technology, Food Safety and Health, Ghent University Faculty of Bioscience Engineering, Ghent, Belgium
| | - Mathias Devreese
- Department of Pharmacology, Toxicology and Biochemistry, Laboratory of Pharmacology and Toxicology, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium
| | - Siska Croubels
- Department of Pharmacology, Toxicology and Biochemistry, Laboratory of Pharmacology and Toxicology, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium
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De Smet J, Boyen F, Croubels S, Rasschaert G, Haesebrouck F, De Backer P, Devreese M. Similar Gastro-Intestinal Exposure to Florfenicol After Oral or Intramuscular Administration in Pigs, Leading to Resistance Selection in Commensal Escherichia coli. Front Pharmacol 2018; 9:1265. [PMID: 30459619 PMCID: PMC6232271 DOI: 10.3389/fphar.2018.01265] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2018] [Accepted: 10/17/2018] [Indexed: 12/24/2022] Open
Abstract
Florfenicol, which is licensed for veterinary use only, proves to be a potent antimicrobial for treatment of respiratory disease. However, the subsequent exposure of the gut microbiota to florfenicol is not well described. Hence, the effect of various administration protocols on both plasma and gastro-intestinal florfenicol concentrations in pigs was evaluated. In field situations were simulated by application of different administration routes and dosages [single oral bolus at 10 or 5 mg/kg body weight (BW), medicated feed at 10 or 5 mg/kg BW and intramuscular injections at 15 or 30 mg/kg BW]. After intramuscular administration of 30 mg florfenicol/kg BW, gastro-intestinal concentrations of florfenicol, quantified 10 h after the last administration, were significantly elevated in comparison with the other treatment groups and ranging between 31.5 and 285.8 μg/g over the different gut segments. For the other treatment groups, the influence of dose and administration route was not significantly different. Bacteriological analysis of the fecal samples from the animals at the start of the experiment, demonstrated the presence of both florfenicol susceptible (with minimal inhibitory concentration (MIC) values of 2-16 μg/mL) and florfenicol resistant (MIC ≥ 256 μg/mL) Escherichia coli isolates in all treatment groups. Following, at 10 h after the last administration the susceptible E. coli population was eradicated in all treatment groups due to the high intestinal florfenicol concentrations measured. Moreover, selection of the resistant E. coli strains during treatment occurred in all groups. This is likely related to the fact that the different treatment strategies led to high gastro-intestinal concentrations albeit not reaching the high magnitude of MIC values associated with florfenicol resistance (≥256 μg/mL). Conclusively, in our experimental setup the administration route and dose alterations studied, had no influence on monitored florfenicol resistance selection in E. coli from the microbiota.
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Affiliation(s)
- Joren De Smet
- Department of Pharmacology, Toxicology and Biochemistry, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
| | - Filip Boyen
- Department of Pathology, Bacteriology and Poultry Diseases, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
| | - Siska Croubels
- Department of Pharmacology, Toxicology and Biochemistry, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
| | - Geertrui Rasschaert
- Technology and Food Science Unit, Flanders Research Institute for Agriculture, Fisheries and Food, Melle, Belgium
| | - Freddy Haesebrouck
- Department of Pathology, Bacteriology and Poultry Diseases, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
| | - Patrick De Backer
- Department of Pharmacology, Toxicology and Biochemistry, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
| | - Mathias Devreese
- Department of Pharmacology, Toxicology and Biochemistry, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
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Mestorino N, Zeinsteger P, Buchamer A, Buldain D, Aliverti F, Marchetti L. Tissue depletion of doxycycline after its oral administration in food producing chicken for fattening. ACTA ACUST UNITED AC 2018. [DOI: 10.15406/ijawb.2018.03.00095] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Filippitzi ME, Chantziaras I, Devreese M, Dewulf J. Probabilistic risk model to assess the potential for resistance selection following the use of anti-microbial medicated feed in pigs. Food Addit Contam Part A Chem Anal Control Expo Risk Assess 2018; 35:1266-1277. [DOI: 10.1080/19440049.2018.1461257] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Affiliation(s)
- Maria Eleni Filippitzi
- Veterinary Epidemiology Unit, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium
| | - Ilias Chantziaras
- Porcine Health Management Unit, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium
| | - Mathias Devreese
- Department of Pharmacology, Toxicology and Biochemistry, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium
| | - Jeroen Dewulf
- Veterinary Epidemiology Unit, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium
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Peeters L, De Mulder T, Van Coillie E, Huygens J, Smet A, Daeseleire E, Dewulf J, Imberechts H, Butaye P, Haesebrouck F, Croubels S, Heyndrickx M, Rasschaert G. Selection and transfer of an IncI1-tet
(A) plasmid of Escherichia coli
in an ex vivo
model of the porcine caecum at doxycycline concentrations caused by crosscontaminated feed. J Appl Microbiol 2017; 123:1312-1320. [DOI: 10.1111/jam.13561] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2017] [Revised: 07/18/2017] [Accepted: 08/04/2017] [Indexed: 11/29/2022]
Affiliation(s)
- L.E.J. Peeters
- Department of General Bacteriology; Veterinary and Agrochemical Research centre; Brussels Belgium
- Department of Pathology, Bacteriology and Avian Diseases; Ghent University; Merelbeke Belgium
| | - T. De Mulder
- Technology and Food Science Unit; Institute for Agricultural and Fisheries Research; Melle Belgium
| | - E. Van Coillie
- Technology and Food Science Unit; Institute for Agricultural and Fisheries Research; Melle Belgium
| | - J. Huygens
- Technology and Food Science Unit; Institute for Agricultural and Fisheries Research; Melle Belgium
| | - A. Smet
- Laboratory Experimental Medicine and Pediatrics; Faculty of Medicine and Health Sciences; University of Antwerp; Antwerp Belgium
| | - E. Daeseleire
- Technology and Food Science Unit; Institute for Agricultural and Fisheries Research; Melle Belgium
| | - J. Dewulf
- Veterinary Epidemiology Unit; Department of Reproduction; Obstetrics and Herd health; Ghent University; Merelbeke Belgium
| | - H. Imberechts
- Department of General Bacteriology; Veterinary and Agrochemical Research centre; Brussels Belgium
| | - P. Butaye
- Department of Pathology, Bacteriology and Avian Diseases; Ghent University; Merelbeke Belgium
- Department of Biosciences; Ross University School of Veterinary Medicine; St Kitts and Nevis West Indies
| | - F. Haesebrouck
- Department of Pathology, Bacteriology and Avian Diseases; Ghent University; Merelbeke Belgium
| | - S. Croubels
- Department of Pharmacology, Toxicology and Biochemistry; Ghent University; Merelbeke Belgium
| | - M. Heyndrickx
- Department of Pathology, Bacteriology and Avian Diseases; Ghent University; Merelbeke Belgium
- Technology and Food Science Unit; Institute for Agricultural and Fisheries Research; Melle Belgium
| | - G. Rasschaert
- Technology and Food Science Unit; Institute for Agricultural and Fisheries Research; Melle Belgium
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