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Antimicrobial resistance (AMR) in bacteria and associated human morbidity and mortality is increasing. The use of antimicrobials in livestock selects for AMR that can subsequently be transferred to humans. This flow of AMR between reservoirs demands surveillance in livestock and in humans. We quantified and characterized the acquired resistance gene pools (resistomes) of 181 pig and 178 poultry farms from nine European countries, sequencing more than 5,000 Gb of DNA using shotgun metagenomics. We quantified acquired AMR using the ResFinder database and a second database constructed for this study, consisting of AMR genes identified through screening environmental DNA. The pig and poultry resistomes were very different in abundance and composition. There was a significant country effect on the resistomes, more so in pigs than in poultry. We found higher AMR loads in pigs, whereas poultry resistomes were more diverse. We detected several recently described, critical AMR genes, including mcr-1 and optrA, the abundance of which differed both between host species and between countries. We found that the total acquired AMR level was associated with the overall country-specific antimicrobial usage in livestock and that countries with comparable usage patterns had similar resistomes. However, functionally determined AMR genes were not associated with total drug use.

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Nature Microbiology, 23 July 2018,

Carbapenems are an important class of β-lactams and one of the last options for treating severe human infections. We present here the complete genome sequence of avian native carbapenemase-producing Salmonella enterica subsp. enterica serovar Corvallis strain 12-01738, harboring a blaNDM-1-carrying IncA/C2 plasmid, isolated in 2012 from a wild bird (Milvus migrans) in Germany.

© 2018 Hadziabdic et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license. Address correspondence to Jennie Fischer,

Genome Announc 6:e00593-18.


The emergence and spread of carbapenemase-producing Enterobacteriaceae (CPE) in wildlife and livestock animals pose an important safety concern for public health. With our in vivo broiler chicken infection study, we investigated the transfer and experimental microevolution of the blaNDM-1-carrying IncA/C2 plasmid (pRH-1238) introduced by avian native Salmonella enterica subsp. enterica serovar Corvallis without inducing antibiotic selection pressure. We evaluated the dependency of the time point of inoculation on donor (S. Corvallis [12-SA01738]) and plasmid-free Salmonella recipient [d-tartrate-fermenting (d-Ta+) S. Paratyphi B (13-SA01617), referred to here as S. Paratyphi B (d-Ta+)] excretion by quantifying their excretion dynamics. Using plasmid profiling by S1 nuclease-restricted pulsed-field gel electrophoresis, we gained insight into the variability of the native plasmid content among S. Corvallis reisolates as well as plasmid acquisition in S. Paratyphi B (d-Ta+) and the enterobacterial gut microflora. Whole-genome sequencing enabled us to gain an in-depth insight into the microevolution of plasmid pRH-1238 in S. Corvallis and enterobacterial recipient isolates. Our study revealed that the fecal excretion of avian native carbapenemase-producing S. Corvallis is significantly higher than that of S. Paratyphi (d-Ta+) and is not hampered by S. Paratyphi (d-Ta+). Acquisition of pRH-1238 in other Enterobacteriaceae and several events of plasmid pRH-1238 transfer to different Escherichia coli sequence types and Klebsiella pneumoniae demonstrated an interspecies broad host range. Regardless of the microevolutionary structural deletions in pRH-1238, the single carbapenem resistance marker blaNDM-1 was maintained on pRH-1238 throughout the trial. Furthermore, we showed the importance of the gut E. coli population as a vector of pRH-1238. In a potential scenario of the introduction of NDM-1-producing S. Corvallis into a broiler flock, the pRH-1238 plasmid could persist and spread to a broad host range even in the absence of antibiotic pressure.

Antimicrobial Agents and Chemotherapy, March 2018, 10.1128/AAC.02128-17

ColE1 plasmids are important vehicles for the spread of antibiotic resistance in the Enterobacteriaceae and Pasteurellaceae families of bacteria. Their monitoring is essential, as they harbor important resistant determinants in humans, animals and the environment. In this work, we have analyzed ColE1 replicons using bioinformatic and experimental approaches. First, we carried out a computational study examining the structure of different ColE1 plasmids deposited in databases. Bioinformatic analysis of these ColE1 replicons revealed a mosaic genetic structure consisting of a host-adapted conserved region responsible for the housekeeping functions of the plasmid, and a variable region encoding a wide variety of genes, including multiple antibiotic resistance determinants. From this exhaustive computational analysis we developed a new PCR-based technique, targeting a specific sequence in the conserved region, for the screening, capture and sequencing of these small plasmids, either specific for Enterobacteriaceae or specific for Pasteurellaceae. To validate this PCR-based system, we tested various collections of isolates from both bacterial families, finding that ColE1 replicons were not only highly prevalent in antibiotic-resistant isolates, but also present in susceptible bacteria. In Pasteurellaceae, ColE1 plasmids carried almost exclusively antibiotic resistance genes. In Enterobacteriaceae, these plasmids encoded a large range of traits, including not only antibiotic resistance determinants, but also a wide variety of genes, showing the huge genetic plasticity of these small replicons. Finally, we also used a metagenomic approach in order to validate this technique, performing this PCR system using total DNA extractions from fecal samples from poultry, turkeys, pigs and humans. Using Illumina sequencing of the PCR products we identified a great diversity of genes encoded by ColE1 replicons, including different antibiotic resistance determinants, supporting the previous results achieved with the collections of bacterial isolates. In addition, we detected cryptic ColE1 plasmids in both families with no known genes in their variable region, which we have named sentinel plasmids. In conclusion, in this work we present a useful genetic tool for the detection and analysis of ColE1 plasmids, and confirm their important role in the dissemination of antibiotic resistance, especially in the Pasteurellaceae family of bacteria.

Frontiers in Microbiology, 16 March 2018,


The World Health Organization has recognized antimicrobial resistance as one of the top three threats to human health. Any use of antibiotics in animals will ultimately affect humans and vice versa. Appropriate monitoring of antimicrobial use and resistance has been repeatedly emphasized along with the need for global policies. Under the auspices of the European Union research project, EFFORT, we mapped antimicrobial use and resistance monitoring programs in ten European countries. We then compared international and European guidelines and policies. In resistance monitoring, we did not find important differences between countries. Current resistance monitoring systems are focused on food animal species (using fecal samples). They ignore companion animals. The scenario is different for monitoring antibiotics use. Recently, countries have tried to harmonize methodologies, but reporting of antimicrobial use remains voluntary. We therefore identified a need for stronger policies.

Keywords: antimicrobial resistance (AMR) monitoring policies animals antimicrobial use (AMU)

J Public Health Pol (2017). doi:10.1057/s41271-017-0067-y

Objectives: Reliable methods for monitoring antimicrobial resistance (AMR) in livestock and other reservoirs are essential to understand the trends, transmission and importance of agricultural resistance. Quantification of AMR is mostly done using culture-based techniques, but metagenomic read mapping shows promise for quantitative resistance monitoring.

Conclusions: We present a workflow, from sampling to interpretation, showing how resistance monitoring can be carried out in swine herds using a metagenomic approach. We propose metagenomic sequencing should be part of routine livestock resistance monitoring programmes and potentially of integrated One Health monitoring in all reservoirs.

J Antimicrob Chemother. 2017 Feb;72(2):385-392. doi: 10.1093/jac/dkw415


IncK plasmids are one of the main carriers of blaCTX-M-14 and blaCMY-2 genes and show high similarity to other plasmids belonging to the I complex, including IncB/O plasmids. Here, we studied the phylogenetic relationship of 37 newly sequenced IncK and IncB/O plasmids. We show that IncK plasmids can be divided into two compatible lineages named IncK1 and IncK2.

Antimicrob Agents Chemother. 2017 Jan 4. pii: AAC.01954-16. doi: 10.1128/AAC.01954-16. [Epub ahead of print]


ColE1 plasmids are small mobilizable replicons that play an important role in the spread of antibiotic resistance in Pasteurellaceae. In this study, we describe how a natural single nucleotide polymorphism (SNP) near the origin of replication of the ColE1-type plasmid pB1000 found in a Pasteurella multocida clinical isolate generates two independent plasmid variants able to coexist in the same cell simultaneously. Using the Haemophilus influenzae Rd KW20 strain as a model system, we combined antibiotic susceptibility tests, quantitative PCRs, competition assays, and experimental evolution to characterize the consequences of the coexistence of the pB1000 plasmid variants. This coexistence produced an increase of the total plasmid copy number (PCN) in the host bacteria, leading to a rise in both the antibiotic resistance level and the metabolic burden produced by pB1000. Using experimental evolution, we showed that in the presence of ampicillin, the bacteria maintained both plasmid variants for 300 generations. In the absence of antibiotics, on the other hand, the bacteria are capable of reverting to the single-plasmid genotype via the loss of one of the plasmid variants. Our results revealed how a single mutation in plasmid pB1000 provides the bacterial host with a mechanism to increase the PCN and, consequently, the ampicillin resistance level. Crucially, this mechanism can be rapidly reversed to avoid the extra cost entailed by the increased PCN in the absence of antibiotics.

Antimicrobial Agents and Chemotherapy, January 2017, 10.1128/AAC.01735-16